CVE-2023-53846
Description
In the Linux kernel, the following vulnerability has been resolved:
f2fs: fix to do sanity check on direct node in truncate_dnode()
syzbot reports below bug:
BUG: KASAN: slab-use-after-free in f2fs_truncate_data_blocks_range+0x122a/0x14c0 fs/f2fs/file.c:574 Read of size 4 at addr ffff88802a25c000 by task syz-executor148/5000
CPU: 1 PID: 5000 Comm: syz-executor148 Not tainted 6.4.0-rc7-syzkaller-00041-ge660abd551f1 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023 Call Trace:
__dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106 print_address_description.constprop.0+0x2c/0x3c0 mm/kasan/report.c:351 print_report mm/kasan/report.c:462 [inline] kasan_report+0x11c/0x130 mm/kasan/report.c:572 f2fs_truncate_data_blocks_range+0x122a/0x14c0 fs/f2fs/file.c:574 truncate_dnode+0x229/0x2e0 fs/f2fs/node.c:944 f2fs_truncate_inode_blocks+0x64b/0xde0 fs/f2fs/node.c:1154 f2fs_do_truncate_blocks+0x4ac/0xf30 fs/f2fs/file.c:721 f2fs_truncate_blocks+0x7b/0x300 fs/f2fs/file.c:749 f2fs_truncate.part.0+0x4a5/0x630 fs/f2fs/file.c:799 f2fs_truncate include/linux/fs.h:825 [inline] f2fs_setattr+0x1738/0x2090 fs/f2fs/file.c:1006 notify_change+0xb2c/0x1180 fs/attr.c:483 do_truncate+0x143/0x200 fs/open.c:66 handle_truncate fs/namei.c:3295 [inline] do_open fs/namei.c:3640 [inline] path_openat+0x2083/0x2750 fs/namei.c:3791 do_filp_open+0x1ba/0x410 fs/namei.c:3818 do_sys_openat2+0x16d/0x4c0 fs/open.c:1356 do_sys_open fs/open.c:1372 [inline] __do_sys_creat fs/open.c:1448 [inline] __se_sys_creat fs/open.c:1442 [inline] __x64_sys_creat+0xcd/0x120 fs/open.c:1442 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd
The root cause is, inodeA references inodeB via inodeB's ino, once inodeA is truncated, it calls truncate_dnode() to truncate data blocks in inodeB's node page, it traverse mapping data from node->i.i_addr[0] to node->i.i_addr[ADDRS_PER_BLOCK() - 1], result in out-of-boundary access.
This patch fixes to add sanity check on dnode page in truncate_dnode(), so that, it can help to avoid triggering such issue, and once it encounters such issue, it will record newly introduced ERROR_INVALID_NODE_REFERENCE error into superblock, later fsck can detect such issue and try repairing.
Also, it removes f2fs_truncate_data_blocks() for cleanup due to the function has only one caller, and uses f2fs_truncate_data_blocks_range() instead.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
A use-after-free in the Linux kernel's f2fs filesystem occurs when truncating a direct node that references another inode's data blocks without proper sanity checks.
Vulnerability
In the Linux kernel's f2fs filesystem, a use-after-free vulnerability exists in the truncate_dnode() function. The root cause is that when inodeA truncates its data blocks, it calls truncate_dnode() to truncate data blocks in inodeB's node page, referencing inodeB via its inode number. The function traverses mapping data from node->i.i_addr[0] to node->i.i_addr[ADDRS_PER_...] is traversed without proper sanity checks, leading to a slab-use-after-free condition [1].
Exploitation
An attacker can trigger this vulnerability by creating a specially crafted filesystem image that causes a direct node to reference another inode's blocks in an invalid way. The attack requires local access to mount the crafted image and perform file operations such as truncate or setattr. No special privileges beyond normal file system access are needed, as the bug is triggered during normal file operations like truncate() or creat() [1].
Impact
Successful exploitation can lead to a kernel crash (denial of service) due to the use-after-free, as demonstrated by the KASAN report. In some cases, it may allow an attacker to escalate privileges or leak sensitive kernel memory, though the primary impact is system instability [1].
Mitigation
The vulnerability was fixed in the Linux kernel by adding a sanity check in truncate_dnode() to verify the validity of the direct node before accessing its data blocks. The fix was committed to the stable kernel tree and is included in subsequent releases. Users should update to a patched kernel version [1].
AI Insight generated on May 19, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.
Affected products
2Patches
2af0f716ad3b0a6ec83786ab9Vulnerability mechanics
Generated on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.
References
2News mentions
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