Unrated severityNVD Advisory· Published May 28, 2026

CVE-2026-46195

Description

In the Linux kernel, the following vulnerability has been resolved:

smb: client: validate dacloffset before building DACL pointers

parse_sec_desc(), build_sec_desc(), and the chown path in id_mode_to_cifs_acl() all add the server-supplied dacloffset to pntsd before proving a DACL header fits inside the returned security descriptor.

On 32-bit builds a malicious server can return dacloffset near U32_MAX, wrap the derived DACL pointer below end_of_acl, and then slip past the later pointer-based bounds checks. build_sec_desc() and id_mode_to_cifs_acl() can then dereference DACL fields from the wrapped pointer in the chmod/chown rewrite paths.

Validate dacloffset numerically before building any DACL pointer and reuse the same helper at the three DACL entry points.

Affected products

SUSE S.A./Linux Enterprise Debuginfoinferred
Ubuntu/Linux Kernelllm-fuzzy

Patches

3b1ddba19e77

smb: client: validate dacloffset before building DACL pointers

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitMichael BommaritoApr 20, 2026Fixed in 6.12.88via kernel-cna

commit

1 file changed · +32 −4

fs/smb/client/cifsacl.c+32 −4 modified

diff --git a/fs/smb/client/cifsacl.c b/fs/smb/client/cifsacl.c
index 1026cbcf1d4fcd..2422ac371262b3 100644
--- a/fs/smb/client/cifsacl.c
+++ b/fs/smb/client/cifsacl.c
@@ -1265,6 +1265,17 @@ static int parse_sid(struct smb_sid *psid, char *end_of_acl)
 	return 0;
 }
 
+static bool dacl_offset_valid(unsigned int acl_len, __u32 dacloffset)
+{
+	if (acl_len < sizeof(struct smb_acl))
+		return false;
+
+	if (dacloffset < sizeof(struct smb_ntsd))
+		return false;
+
+	return dacloffset <= acl_len - sizeof(struct smb_acl);
+}
+
 
 /* Convert CIFS ACL to POSIX form */
 static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
@@ -1285,7 +1296,6 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 	group_sid_ptr = (struct smb_sid *)((char *)pntsd +
 				le32_to_cpu(pntsd->gsidoffset));
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
-	dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 	cifs_dbg(NOISY, "revision %d type 0x%x ooffset 0x%x goffset 0x%x sacloffset 0x%x dacloffset 0x%x\n",
 		 pntsd->revision, pntsd->type, le32_to_cpu(pntsd->osidoffset),
 		 le32_to_cpu(pntsd->gsidoffset),
@@ -1316,11 +1326,18 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 		return rc;
 	}
 
-	if (dacloffset)
+	if (dacloffset) {
+		if (!dacl_offset_valid(acl_len, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
+		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		parse_dacl(dacl_ptr, end_of_acl, owner_sid_ptr,
 			   group_sid_ptr, fattr, get_mode_from_special_sid);
-	else
+	} else {
 		cifs_dbg(FYI, "no ACL\n"); /* BB grant all or default perms? */
+	}
 
 	return rc;
 }
@@ -1343,6 +1360,11 @@ static int build_sec_desc(struct smb_ntsd *pntsd, struct smb_ntsd *pnntsd,
 
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
 	if (dacloffset) {
+		if (!dacl_offset_valid(secdesclen, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
 		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		rc = validate_dacl(dacl_ptr, end_of_acl);
 		if (rc)
@@ -1716,6 +1738,12 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		nsecdesclen = sizeof(struct smb_ntsd) + (sizeof(struct smb_sid) * 2);
 		dacloffset = le32_to_cpu(pntsd->dacloffset);
 		if (dacloffset) {
+			if (!dacl_offset_valid(secdesclen, dacloffset)) {
+				cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+				rc = -EINVAL;
+				goto id_mode_to_cifs_acl_exit;
+			}
+
 			dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 			rc = validate_dacl(dacl_ptr, (char *)pntsd + secdesclen);
 			if (rc) {
@@ -1758,6 +1786,7 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		rc = ops->set_acl(pnntsd, nsecdesclen, inode, path, aclflag);
 		cifs_dbg(NOISY, "set_cifs_acl rc: %d\n", rc);
 	}
+id_mode_to_cifs_acl_exit:
 	cifs_put_tlink(tlink);
 
 	kfree(pnntsd);
-- 
cgit 1.3-korg

c688f3ed73d3

smb: client: validate dacloffset before building DACL pointers

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitMichael BommaritoApr 20, 2026Fixed in 6.18.30via kernel-cna

commit

1 file changed · +32 −4

fs/smb/client/cifsacl.c+32 −4 modified

diff --git a/fs/smb/client/cifsacl.c b/fs/smb/client/cifsacl.c
index 5b43d5ddfd94ad..e2948835587094 100644
--- a/fs/smb/client/cifsacl.c
+++ b/fs/smb/client/cifsacl.c
@@ -1215,6 +1215,17 @@ static int parse_sid(struct smb_sid *psid, char *end_of_acl)
 	return 0;
 }
 
+static bool dacl_offset_valid(unsigned int acl_len, __u32 dacloffset)
+{
+	if (acl_len < sizeof(struct smb_acl))
+		return false;
+
+	if (dacloffset < sizeof(struct smb_ntsd))
+		return false;
+
+	return dacloffset <= acl_len - sizeof(struct smb_acl);
+}
+
 
 /* Convert CIFS ACL to POSIX form */
 static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
@@ -1235,7 +1246,6 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 	group_sid_ptr = (struct smb_sid *)((char *)pntsd +
 				le32_to_cpu(pntsd->gsidoffset));
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
-	dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 	cifs_dbg(NOISY, "revision %d type 0x%x ooffset 0x%x goffset 0x%x sacloffset 0x%x dacloffset 0x%x\n",
 		 pntsd->revision, pntsd->type, le32_to_cpu(pntsd->osidoffset),
 		 le32_to_cpu(pntsd->gsidoffset),
@@ -1266,11 +1276,18 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 		return rc;
 	}
 
-	if (dacloffset)
+	if (dacloffset) {
+		if (!dacl_offset_valid(acl_len, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
+		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		parse_dacl(dacl_ptr, end_of_acl, owner_sid_ptr,
 			   group_sid_ptr, fattr, get_mode_from_special_sid);
-	else
+	} else {
 		cifs_dbg(FYI, "no ACL\n"); /* BB grant all or default perms? */
+	}
 
 	return rc;
 }
@@ -1293,6 +1310,11 @@ static int build_sec_desc(struct smb_ntsd *pntsd, struct smb_ntsd *pnntsd,
 
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
 	if (dacloffset) {
+		if (!dacl_offset_valid(secdesclen, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
 		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		if (end_of_acl < (char *)dacl_ptr + le16_to_cpu(dacl_ptr->size)) {
 			cifs_dbg(VFS, "Server returned illegal ACL size\n");
@@ -1669,6 +1691,12 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		nsecdesclen = sizeof(struct smb_ntsd) + (sizeof(struct smb_sid) * 2);
 		dacloffset = le32_to_cpu(pntsd->dacloffset);
 		if (dacloffset) {
+			if (!dacl_offset_valid(secdesclen, dacloffset)) {
+				cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+				rc = -EINVAL;
+				goto id_mode_to_cifs_acl_exit;
+			}
+
 			dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 			if (mode_from_sid)
 				nsecdesclen +=
@@ -1705,6 +1733,7 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		rc = ops->set_acl(pnntsd, nsecdesclen, inode, path, aclflag);
 		cifs_dbg(NOISY, "set_cifs_acl rc: %d\n", rc);
 	}
+id_mode_to_cifs_acl_exit:
 	cifs_put_tlink(tlink);
 
 	kfree(pnntsd);
-- 
cgit 1.3-korg

8bd07e417b6b

smb: client: validate dacloffset before building DACL pointers

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitMichael BommaritoApr 20, 2026Fixed in 7.0.7via kernel-cna

commit

1 file changed · +32 −4

fs/smb/client/cifsacl.c+32 −4 modified

diff --git a/fs/smb/client/cifsacl.c b/fs/smb/client/cifsacl.c
index 62fccba6fede72..e5d0d581c130bf 100644
--- a/fs/smb/client/cifsacl.c
+++ b/fs/smb/client/cifsacl.c
@@ -1264,6 +1264,17 @@ static int parse_sid(struct smb_sid *psid, char *end_of_acl)
 	return 0;
 }
 
+static bool dacl_offset_valid(unsigned int acl_len, __u32 dacloffset)
+{
+	if (acl_len < sizeof(struct smb_acl))
+		return false;
+
+	if (dacloffset < sizeof(struct smb_ntsd))
+		return false;
+
+	return dacloffset <= acl_len - sizeof(struct smb_acl);
+}
+
 
 /* Convert CIFS ACL to POSIX form */
 static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
@@ -1284,7 +1295,6 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 	group_sid_ptr = (struct smb_sid *)((char *)pntsd +
 				le32_to_cpu(pntsd->gsidoffset));
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
-	dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 	cifs_dbg(NOISY, "revision %d type 0x%x ooffset 0x%x goffset 0x%x sacloffset 0x%x dacloffset 0x%x\n",
 		 pntsd->revision, pntsd->type, le32_to_cpu(pntsd->osidoffset),
 		 le32_to_cpu(pntsd->gsidoffset),
@@ -1315,11 +1325,18 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 		return rc;
 	}
 
-	if (dacloffset)
+	if (dacloffset) {
+		if (!dacl_offset_valid(acl_len, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
+		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		parse_dacl(dacl_ptr, end_of_acl, owner_sid_ptr,
 			   group_sid_ptr, fattr, get_mode_from_special_sid);
-	else
+	} else {
 		cifs_dbg(FYI, "no ACL\n"); /* BB grant all or default perms? */
+	}
 
 	return rc;
 }
@@ -1342,6 +1359,11 @@ static int build_sec_desc(struct smb_ntsd *pntsd, struct smb_ntsd *pnntsd,
 
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
 	if (dacloffset) {
+		if (!dacl_offset_valid(secdesclen, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
 		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		rc = validate_dacl(dacl_ptr, end_of_acl);
 		if (rc)
@@ -1710,6 +1732,12 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		nsecdesclen = sizeof(struct smb_ntsd) + (sizeof(struct smb_sid) * 2);
 		dacloffset = le32_to_cpu(pntsd->dacloffset);
 		if (dacloffset) {
+			if (!dacl_offset_valid(secdesclen, dacloffset)) {
+				cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+				rc = -EINVAL;
+				goto id_mode_to_cifs_acl_exit;
+			}
+
 			dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 			rc = validate_dacl(dacl_ptr, (char *)pntsd + secdesclen);
 			if (rc) {
@@ -1752,6 +1780,7 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		rc = ops->set_acl(pnntsd, nsecdesclen, inode, path, aclflag);
 		cifs_dbg(NOISY, "set_cifs_acl rc: %d\n", rc);
 	}
+id_mode_to_cifs_acl_exit:
 	cifs_put_tlink(tlink);
 
 	kfree(pnntsd);
-- 
cgit 1.3-korg

f98b48151cc5

smb: client: validate dacloffset before building DACL pointers

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitMichael BommaritoApr 20, 2026Fixed in 7.1-rc3via kernel-cna

commit

1 file changed · +32 −4

fs/smb/client/cifsacl.c+32 −4 modified

diff --git a/fs/smb/client/cifsacl.c b/fs/smb/client/cifsacl.c
index a2750f1e3d90bd..786dbbc43c5b99 100644
--- a/fs/smb/client/cifsacl.c
+++ b/fs/smb/client/cifsacl.c
@@ -1264,6 +1264,17 @@ static int parse_sid(struct smb_sid *psid, char *end_of_acl)
 	return 0;
 }
 
+static bool dacl_offset_valid(unsigned int acl_len, __u32 dacloffset)
+{
+	if (acl_len < sizeof(struct smb_acl))
+		return false;
+
+	if (dacloffset < sizeof(struct smb_ntsd))
+		return false;
+
+	return dacloffset <= acl_len - sizeof(struct smb_acl);
+}
+
 
 /* Convert CIFS ACL to POSIX form */
 static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
@@ -1284,7 +1295,6 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 	group_sid_ptr = (struct smb_sid *)((char *)pntsd +
 				le32_to_cpu(pntsd->gsidoffset));
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
-	dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 	cifs_dbg(NOISY, "revision %d type 0x%x ooffset 0x%x goffset 0x%x sacloffset 0x%x dacloffset 0x%x\n",
 		 pntsd->revision, pntsd->type, le32_to_cpu(pntsd->osidoffset),
 		 le32_to_cpu(pntsd->gsidoffset),
@@ -1315,11 +1325,18 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 		return rc;
 	}
 
-	if (dacloffset)
+	if (dacloffset) {
+		if (!dacl_offset_valid(acl_len, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
+		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		parse_dacl(dacl_ptr, end_of_acl, owner_sid_ptr,
 			   group_sid_ptr, fattr, get_mode_from_special_sid);
-	else
+	} else {
 		cifs_dbg(FYI, "no ACL\n"); /* BB grant all or default perms? */
+	}
 
 	return rc;
 }
@@ -1342,6 +1359,11 @@ static int build_sec_desc(struct smb_ntsd *pntsd, struct smb_ntsd *pnntsd,
 
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
 	if (dacloffset) {
+		if (!dacl_offset_valid(secdesclen, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
 		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		rc = validate_dacl(dacl_ptr, end_of_acl);
 		if (rc)
@@ -1710,6 +1732,12 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		nsecdesclen = sizeof(struct smb_ntsd) + (sizeof(struct smb_sid) * 2);
 		dacloffset = le32_to_cpu(pntsd->dacloffset);
 		if (dacloffset) {
+			if (!dacl_offset_valid(secdesclen, dacloffset)) {
+				cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+				rc = -EINVAL;
+				goto id_mode_to_cifs_acl_exit;
+			}
+
 			dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 			rc = validate_dacl(dacl_ptr, (char *)pntsd + secdesclen);
 			if (rc) {
@@ -1752,6 +1780,7 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		rc = ops->set_acl(pnntsd, nsecdesclen, inode, path, aclflag);
 		cifs_dbg(NOISY, "set_cifs_acl rc: %d\n", rc);
 	}
+id_mode_to_cifs_acl_exit:
 	cifs_put_tlink(tlink);
 
 	kfree(pnntsd);
-- 
cgit 1.3-korg

ba7f71b6161c

smb: client: validate dacloffset before building DACL pointers

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitMichael BommaritoApr 20, 2026Fixed in 6.6.140via kernel-cna

commit

1 file changed · +32 −4

fs/smb/client/cifsacl.c+32 −4 modified

diff --git a/fs/smb/client/cifsacl.c b/fs/smb/client/cifsacl.c
index fb090e001e444e..48d78a41b8afe1 100644
--- a/fs/smb/client/cifsacl.c
+++ b/fs/smb/client/cifsacl.c
@@ -1216,6 +1216,17 @@ static int parse_sid(struct smb_sid *psid, char *end_of_acl)
 	return 0;
 }
 
+static bool dacl_offset_valid(unsigned int acl_len, __u32 dacloffset)
+{
+	if (acl_len < sizeof(struct smb_acl))
+		return false;
+
+	if (dacloffset < sizeof(struct smb_ntsd))
+		return false;
+
+	return dacloffset <= acl_len - sizeof(struct smb_acl);
+}
+
 
 /* Convert CIFS ACL to POSIX form */
 static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
@@ -1236,7 +1247,6 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 	group_sid_ptr = (struct smb_sid *)((char *)pntsd +
 				le32_to_cpu(pntsd->gsidoffset));
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
-	dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 	cifs_dbg(NOISY, "revision %d type 0x%x ooffset 0x%x goffset 0x%x sacloffset 0x%x dacloffset 0x%x\n",
 		 pntsd->revision, pntsd->type, le32_to_cpu(pntsd->osidoffset),
 		 le32_to_cpu(pntsd->gsidoffset),
@@ -1267,11 +1277,18 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 		return rc;
 	}
 
-	if (dacloffset)
+	if (dacloffset) {
+		if (!dacl_offset_valid(acl_len, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
+		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		parse_dacl(dacl_ptr, end_of_acl, owner_sid_ptr,
 			   group_sid_ptr, fattr, get_mode_from_special_sid);
-	else
+	} else {
 		cifs_dbg(FYI, "no ACL\n"); /* BB grant all or default perms? */
+	}
 
 	return rc;
 }
@@ -1294,6 +1311,11 @@ static int build_sec_desc(struct smb_ntsd *pntsd, struct smb_ntsd *pnntsd,
 
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
 	if (dacloffset) {
+		if (!dacl_offset_valid(secdesclen, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
 		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		if (end_of_acl < (char *)dacl_ptr + le16_to_cpu(dacl_ptr->size)) {
 			cifs_dbg(VFS, "Server returned illegal ACL size\n");
@@ -1668,6 +1690,12 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		nsecdesclen = sizeof(struct smb_ntsd) + (sizeof(struct smb_sid) * 2);
 		dacloffset = le32_to_cpu(pntsd->dacloffset);
 		if (dacloffset) {
+			if (!dacl_offset_valid(secdesclen, dacloffset)) {
+				cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+				rc = -EINVAL;
+				goto id_mode_to_cifs_acl_exit;
+			}
+
 			dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 			if (mode_from_sid)
 				nsecdesclen +=
@@ -1704,6 +1732,7 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		rc = ops->set_acl(pnntsd, nsecdesclen, inode, path, aclflag);
 		cifs_dbg(NOISY, "set_cifs_acl rc: %d\n", rc);
 	}
+id_mode_to_cifs_acl_exit:
 	cifs_put_tlink(tlink);
 
 	kfree(pnntsd);
-- 
cgit 1.3-korg

f98b48151cc5

smb: client: validate dacloffset before building DACL pointers

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.gitMichael BommaritoApr 20, 2026via nvd-ref

commit

1 file changed · +32 −4

fs/smb/client/cifsacl.c+32 −4 modified

diff --git a/fs/smb/client/cifsacl.c b/fs/smb/client/cifsacl.c
index a2750f1e3d90bd..786dbbc43c5b99 100644
--- a/fs/smb/client/cifsacl.c
+++ b/fs/smb/client/cifsacl.c
@@ -1264,6 +1264,17 @@ static int parse_sid(struct smb_sid *psid, char *end_of_acl)
 	return 0;
 }
 
+static bool dacl_offset_valid(unsigned int acl_len, __u32 dacloffset)
+{
+	if (acl_len < sizeof(struct smb_acl))
+		return false;
+
+	if (dacloffset < sizeof(struct smb_ntsd))
+		return false;
+
+	return dacloffset <= acl_len - sizeof(struct smb_acl);
+}
+
 
 /* Convert CIFS ACL to POSIX form */
 static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
@@ -1284,7 +1295,6 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 	group_sid_ptr = (struct smb_sid *)((char *)pntsd +
 				le32_to_cpu(pntsd->gsidoffset));
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
-	dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 	cifs_dbg(NOISY, "revision %d type 0x%x ooffset 0x%x goffset 0x%x sacloffset 0x%x dacloffset 0x%x\n",
 		 pntsd->revision, pntsd->type, le32_to_cpu(pntsd->osidoffset),
 		 le32_to_cpu(pntsd->gsidoffset),
@@ -1315,11 +1325,18 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 		return rc;
 	}
 
-	if (dacloffset)
+	if (dacloffset) {
+		if (!dacl_offset_valid(acl_len, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
+		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		parse_dacl(dacl_ptr, end_of_acl, owner_sid_ptr,
 			   group_sid_ptr, fattr, get_mode_from_special_sid);
-	else
+	} else {
 		cifs_dbg(FYI, "no ACL\n"); /* BB grant all or default perms? */
+	}
 
 	return rc;
 }
@@ -1342,6 +1359,11 @@ static int build_sec_desc(struct smb_ntsd *pntsd, struct smb_ntsd *pnntsd,
 
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
 	if (dacloffset) {
+		if (!dacl_offset_valid(secdesclen, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
 		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		rc = validate_dacl(dacl_ptr, end_of_acl);
 		if (rc)
@@ -1710,6 +1732,12 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		nsecdesclen = sizeof(struct smb_ntsd) + (sizeof(struct smb_sid) * 2);
 		dacloffset = le32_to_cpu(pntsd->dacloffset);
 		if (dacloffset) {
+			if (!dacl_offset_valid(secdesclen, dacloffset)) {
+				cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+				rc = -EINVAL;
+				goto id_mode_to_cifs_acl_exit;
+			}
+
 			dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 			rc = validate_dacl(dacl_ptr, (char *)pntsd + secdesclen);
 			if (rc) {
@@ -1752,6 +1780,7 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		rc = ops->set_acl(pnntsd, nsecdesclen, inode, path, aclflag);
 		cifs_dbg(NOISY, "set_cifs_acl rc: %d\n", rc);
 	}
+id_mode_to_cifs_acl_exit:
 	cifs_put_tlink(tlink);
 
 	kfree(pnntsd);
-- 
cgit 1.3-korg

8bd07e417b6b

smb: client: validate dacloffset before building DACL pointers

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.gitMichael BommaritoApr 20, 2026via nvd-ref

commit

1 file changed · +32 −4

fs/smb/client/cifsacl.c+32 −4 modified

diff --git a/fs/smb/client/cifsacl.c b/fs/smb/client/cifsacl.c
index 62fccba6fede72..e5d0d581c130bf 100644
--- a/fs/smb/client/cifsacl.c
+++ b/fs/smb/client/cifsacl.c
@@ -1264,6 +1264,17 @@ static int parse_sid(struct smb_sid *psid, char *end_of_acl)
 	return 0;
 }
 
+static bool dacl_offset_valid(unsigned int acl_len, __u32 dacloffset)
+{
+	if (acl_len < sizeof(struct smb_acl))
+		return false;
+
+	if (dacloffset < sizeof(struct smb_ntsd))
+		return false;
+
+	return dacloffset <= acl_len - sizeof(struct smb_acl);
+}
+
 
 /* Convert CIFS ACL to POSIX form */
 static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
@@ -1284,7 +1295,6 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 	group_sid_ptr = (struct smb_sid *)((char *)pntsd +
 				le32_to_cpu(pntsd->gsidoffset));
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
-	dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 	cifs_dbg(NOISY, "revision %d type 0x%x ooffset 0x%x goffset 0x%x sacloffset 0x%x dacloffset 0x%x\n",
 		 pntsd->revision, pntsd->type, le32_to_cpu(pntsd->osidoffset),
 		 le32_to_cpu(pntsd->gsidoffset),
@@ -1315,11 +1325,18 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 		return rc;
 	}
 
-	if (dacloffset)
+	if (dacloffset) {
+		if (!dacl_offset_valid(acl_len, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
+		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		parse_dacl(dacl_ptr, end_of_acl, owner_sid_ptr,
 			   group_sid_ptr, fattr, get_mode_from_special_sid);
-	else
+	} else {
 		cifs_dbg(FYI, "no ACL\n"); /* BB grant all or default perms? */
+	}
 
 	return rc;
 }
@@ -1342,6 +1359,11 @@ static int build_sec_desc(struct smb_ntsd *pntsd, struct smb_ntsd *pnntsd,
 
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
 	if (dacloffset) {
+		if (!dacl_offset_valid(secdesclen, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
 		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		rc = validate_dacl(dacl_ptr, end_of_acl);
 		if (rc)
@@ -1710,6 +1732,12 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		nsecdesclen = sizeof(struct smb_ntsd) + (sizeof(struct smb_sid) * 2);
 		dacloffset = le32_to_cpu(pntsd->dacloffset);
 		if (dacloffset) {
+			if (!dacl_offset_valid(secdesclen, dacloffset)) {
+				cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+				rc = -EINVAL;
+				goto id_mode_to_cifs_acl_exit;
+			}
+
 			dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 			rc = validate_dacl(dacl_ptr, (char *)pntsd + secdesclen);
 			if (rc) {
@@ -1752,6 +1780,7 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		rc = ops->set_acl(pnntsd, nsecdesclen, inode, path, aclflag);
 		cifs_dbg(NOISY, "set_cifs_acl rc: %d\n", rc);
 	}
+id_mode_to_cifs_acl_exit:
 	cifs_put_tlink(tlink);
 
 	kfree(pnntsd);
-- 
cgit 1.3-korg

ba7f71b6161c

smb: client: validate dacloffset before building DACL pointers

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.gitMichael BommaritoApr 20, 2026via nvd-ref

commit

1 file changed · +32 −4

fs/smb/client/cifsacl.c+32 −4 modified

diff --git a/fs/smb/client/cifsacl.c b/fs/smb/client/cifsacl.c
index fb090e001e444e..48d78a41b8afe1 100644
--- a/fs/smb/client/cifsacl.c
+++ b/fs/smb/client/cifsacl.c
@@ -1216,6 +1216,17 @@ static int parse_sid(struct smb_sid *psid, char *end_of_acl)
 	return 0;
 }
 
+static bool dacl_offset_valid(unsigned int acl_len, __u32 dacloffset)
+{
+	if (acl_len < sizeof(struct smb_acl))
+		return false;
+
+	if (dacloffset < sizeof(struct smb_ntsd))
+		return false;
+
+	return dacloffset <= acl_len - sizeof(struct smb_acl);
+}
+
 
 /* Convert CIFS ACL to POSIX form */
 static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
@@ -1236,7 +1247,6 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 	group_sid_ptr = (struct smb_sid *)((char *)pntsd +
 				le32_to_cpu(pntsd->gsidoffset));
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
-	dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 	cifs_dbg(NOISY, "revision %d type 0x%x ooffset 0x%x goffset 0x%x sacloffset 0x%x dacloffset 0x%x\n",
 		 pntsd->revision, pntsd->type, le32_to_cpu(pntsd->osidoffset),
 		 le32_to_cpu(pntsd->gsidoffset),
@@ -1267,11 +1277,18 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 		return rc;
 	}
 
-	if (dacloffset)
+	if (dacloffset) {
+		if (!dacl_offset_valid(acl_len, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
+		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		parse_dacl(dacl_ptr, end_of_acl, owner_sid_ptr,
 			   group_sid_ptr, fattr, get_mode_from_special_sid);
-	else
+	} else {
 		cifs_dbg(FYI, "no ACL\n"); /* BB grant all or default perms? */
+	}
 
 	return rc;
 }
@@ -1294,6 +1311,11 @@ static int build_sec_desc(struct smb_ntsd *pntsd, struct smb_ntsd *pnntsd,
 
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
 	if (dacloffset) {
+		if (!dacl_offset_valid(secdesclen, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
 		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		if (end_of_acl < (char *)dacl_ptr + le16_to_cpu(dacl_ptr->size)) {
 			cifs_dbg(VFS, "Server returned illegal ACL size\n");
@@ -1668,6 +1690,12 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		nsecdesclen = sizeof(struct smb_ntsd) + (sizeof(struct smb_sid) * 2);
 		dacloffset = le32_to_cpu(pntsd->dacloffset);
 		if (dacloffset) {
+			if (!dacl_offset_valid(secdesclen, dacloffset)) {
+				cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+				rc = -EINVAL;
+				goto id_mode_to_cifs_acl_exit;
+			}
+
 			dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 			if (mode_from_sid)
 				nsecdesclen +=
@@ -1704,6 +1732,7 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		rc = ops->set_acl(pnntsd, nsecdesclen, inode, path, aclflag);
 		cifs_dbg(NOISY, "set_cifs_acl rc: %d\n", rc);
 	}
+id_mode_to_cifs_acl_exit:
 	cifs_put_tlink(tlink);
 
 	kfree(pnntsd);
-- 
cgit 1.3-korg

c688f3ed73d3

smb: client: validate dacloffset before building DACL pointers

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.gitMichael BommaritoApr 20, 2026via nvd-ref

commit

1 file changed · +32 −4

fs/smb/client/cifsacl.c+32 −4 modified

diff --git a/fs/smb/client/cifsacl.c b/fs/smb/client/cifsacl.c
index 5b43d5ddfd94ad..e2948835587094 100644
--- a/fs/smb/client/cifsacl.c
+++ b/fs/smb/client/cifsacl.c
@@ -1215,6 +1215,17 @@ static int parse_sid(struct smb_sid *psid, char *end_of_acl)
 	return 0;
 }
 
+static bool dacl_offset_valid(unsigned int acl_len, __u32 dacloffset)
+{
+	if (acl_len < sizeof(struct smb_acl))
+		return false;
+
+	if (dacloffset < sizeof(struct smb_ntsd))
+		return false;
+
+	return dacloffset <= acl_len - sizeof(struct smb_acl);
+}
+
 
 /* Convert CIFS ACL to POSIX form */
 static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
@@ -1235,7 +1246,6 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 	group_sid_ptr = (struct smb_sid *)((char *)pntsd +
 				le32_to_cpu(pntsd->gsidoffset));
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
-	dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 	cifs_dbg(NOISY, "revision %d type 0x%x ooffset 0x%x goffset 0x%x sacloffset 0x%x dacloffset 0x%x\n",
 		 pntsd->revision, pntsd->type, le32_to_cpu(pntsd->osidoffset),
 		 le32_to_cpu(pntsd->gsidoffset),
@@ -1266,11 +1276,18 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 		return rc;
 	}
 
-	if (dacloffset)
+	if (dacloffset) {
+		if (!dacl_offset_valid(acl_len, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
+		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		parse_dacl(dacl_ptr, end_of_acl, owner_sid_ptr,
 			   group_sid_ptr, fattr, get_mode_from_special_sid);
-	else
+	} else {
 		cifs_dbg(FYI, "no ACL\n"); /* BB grant all or default perms? */
+	}
 
 	return rc;
 }
@@ -1293,6 +1310,11 @@ static int build_sec_desc(struct smb_ntsd *pntsd, struct smb_ntsd *pnntsd,
 
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
 	if (dacloffset) {
+		if (!dacl_offset_valid(secdesclen, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
 		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		if (end_of_acl < (char *)dacl_ptr + le16_to_cpu(dacl_ptr->size)) {
 			cifs_dbg(VFS, "Server returned illegal ACL size\n");
@@ -1669,6 +1691,12 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		nsecdesclen = sizeof(struct smb_ntsd) + (sizeof(struct smb_sid) * 2);
 		dacloffset = le32_to_cpu(pntsd->dacloffset);
 		if (dacloffset) {
+			if (!dacl_offset_valid(secdesclen, dacloffset)) {
+				cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+				rc = -EINVAL;
+				goto id_mode_to_cifs_acl_exit;
+			}
+
 			dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 			if (mode_from_sid)
 				nsecdesclen +=
@@ -1705,6 +1733,7 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		rc = ops->set_acl(pnntsd, nsecdesclen, inode, path, aclflag);
 		cifs_dbg(NOISY, "set_cifs_acl rc: %d\n", rc);
 	}
+id_mode_to_cifs_acl_exit:
 	cifs_put_tlink(tlink);
 
 	kfree(pnntsd);
-- 
cgit 1.3-korg

3b1ddba19e77

smb: client: validate dacloffset before building DACL pointers

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.gitMichael BommaritoApr 20, 2026via nvd-ref

commit

1 file changed · +32 −4

fs/smb/client/cifsacl.c+32 −4 modified

diff --git a/fs/smb/client/cifsacl.c b/fs/smb/client/cifsacl.c
index 1026cbcf1d4fcd..2422ac371262b3 100644
--- a/fs/smb/client/cifsacl.c
+++ b/fs/smb/client/cifsacl.c
@@ -1265,6 +1265,17 @@ static int parse_sid(struct smb_sid *psid, char *end_of_acl)
 	return 0;
 }
 
+static bool dacl_offset_valid(unsigned int acl_len, __u32 dacloffset)
+{
+	if (acl_len < sizeof(struct smb_acl))
+		return false;
+
+	if (dacloffset < sizeof(struct smb_ntsd))
+		return false;
+
+	return dacloffset <= acl_len - sizeof(struct smb_acl);
+}
+
 
 /* Convert CIFS ACL to POSIX form */
 static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
@@ -1285,7 +1296,6 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 	group_sid_ptr = (struct smb_sid *)((char *)pntsd +
 				le32_to_cpu(pntsd->gsidoffset));
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
-	dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 	cifs_dbg(NOISY, "revision %d type 0x%x ooffset 0x%x goffset 0x%x sacloffset 0x%x dacloffset 0x%x\n",
 		 pntsd->revision, pntsd->type, le32_to_cpu(pntsd->osidoffset),
 		 le32_to_cpu(pntsd->gsidoffset),
@@ -1316,11 +1326,18 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 		return rc;
 	}
 
-	if (dacloffset)
+	if (dacloffset) {
+		if (!dacl_offset_valid(acl_len, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
+		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		parse_dacl(dacl_ptr, end_of_acl, owner_sid_ptr,
 			   group_sid_ptr, fattr, get_mode_from_special_sid);
-	else
+	} else {
 		cifs_dbg(FYI, "no ACL\n"); /* BB grant all or default perms? */
+	}
 
 	return rc;
 }
@@ -1343,6 +1360,11 @@ static int build_sec_desc(struct smb_ntsd *pntsd, struct smb_ntsd *pnntsd,
 
 	dacloffset = le32_to_cpu(pntsd->dacloffset);
 	if (dacloffset) {
+		if (!dacl_offset_valid(secdesclen, dacloffset)) {
+			cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+			return -EINVAL;
+		}
+
 		dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 		rc = validate_dacl(dacl_ptr, end_of_acl);
 		if (rc)
@@ -1716,6 +1738,12 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		nsecdesclen = sizeof(struct smb_ntsd) + (sizeof(struct smb_sid) * 2);
 		dacloffset = le32_to_cpu(pntsd->dacloffset);
 		if (dacloffset) {
+			if (!dacl_offset_valid(secdesclen, dacloffset)) {
+				cifs_dbg(VFS, "Server returned illegal DACL offset\n");
+				rc = -EINVAL;
+				goto id_mode_to_cifs_acl_exit;
+			}
+
 			dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset);
 			rc = validate_dacl(dacl_ptr, (char *)pntsd + secdesclen);
 			if (rc) {
@@ -1758,6 +1786,7 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 		rc = ops->set_acl(pnntsd, nsecdesclen, inode, path, aclflag);
 		cifs_dbg(NOISY, "set_cifs_acl rc: %d\n", rc);
 	}
+id_mode_to_cifs_acl_exit:
 	cifs_put_tlink(tlink);
 
 	kfree(pnntsd);
-- 
cgit 1.3-korg

Vulnerability mechanics

Root cause

"Missing numerical validation of the server-supplied dacloffset before pointer arithmetic, allowing integer wrap on 32-bit builds to bypass later pointer-based bounds checks."

Attack vector

A malicious SMB server sends a crafted security descriptor with a dacloffset value near U32_MAX. On 32-bit client builds, adding this offset to the base pointer wraps the resulting DACL pointer below end_of_acl, causing the subsequent pointer-based bounds checks to pass. The attacker can then trigger the chmod/chown rewrite paths in build_sec_desc() or id_mode_to_cifs_acl(), which dereference DACL fields from the wrapped pointer, leading to out-of-bounds read/write [patch_id=2897865]. No authentication beyond normal SMB session establishment is required; the server simply returns the malicious descriptor in any SMB2/3 query operation that includes a security descriptor.

Affected code

The vulnerability exists in fs/smb/client/cifsacl.c in three functions: parse_sec_desc(), build_sec_desc(), and id_mode_to_cifs_acl(). All three compute a DACL pointer by adding the server-supplied dacloffset to pntsd without first validating the offset numerically [patch_id=2897865].

What the fix does

The patch introduces a new helper function dacl_offset_valid() that performs a numerical bounds check on dacloffset before any pointer is constructed [patch_id=2897865]. It verifies that the ACL length is at least sizeof(struct smb_acl), that dacloffset is at least sizeof(struct smb_ntsd), and that dacloffset does not exceed acl_len - sizeof(struct smb_acl). This check is inserted at all three DACL entry points — parse_sec_desc(), build_sec_desc(), and id_mode_to_cifs_acl() — before the pointer (char *)pntsd + dacloffset is computed. If the offset is invalid, the function returns -EINVAL and logs a warning, preventing any DACL pointer from being built from a malicious offset.

Preconditions

configClient must be running a 32-bit kernel build where pointer arithmetic can wrap
networkAttacker must control a malicious SMB server that the client connects to
inputClient must perform an operation that parses a security descriptor (e.g., stat, chmod, chown on a CIFS/SMB mount)

Generated on May 28, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.

References

News mentions

No linked articles in our index yet.

cvss	0.000
epss	0.000
exploit	0.000
kev	0.000
patch	-0.070
ransomware	0.000