CVE-2025-68337
Description
In the Linux kernel, the following vulnerability has been resolved:
jbd2: avoid bug_on in jbd2_journal_get_create_access() when file system corrupted
There's issue when file system corrupted: ------------[ cut here ]------------ kernel BUG at fs/jbd2/transaction.c:1289! Oops: invalid opcode: 0000 [#1] SMP KASAN PTI CPU: 5 UID: 0 PID: 2031 Comm: mkdir Not tainted 6.18.0-rc1-next RIP: 0010:jbd2_journal_get_create_access+0x3b6/0x4d0 RSP: 0018:ffff888117aafa30 EFLAGS: 00010202 RAX: 0000000000000000 RBX: ffff88811a86b000 RCX: ffffffff89a63534 RDX: 1ffff110200ec602 RSI: 0000000000000004 RDI: ffff888100763010 RBP: ffff888100763000 R08: 0000000000000001 R09: ffff888100763028 R10: 0000000000000003 R11: 0000000000000000 R12: 0000000000000000 R13: ffff88812c432000 R14: ffff88812c608000 R15: ffff888120bfc000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f91d6970c99 CR3: 00000001159c4000 CR4: 00000000000006f0 Call Trace:
__ext4_journal_get_create_access+0x42/0x170 ext4_getblk+0x319/0x6f0 ext4_bread+0x11/0x100 ext4_append+0x1e6/0x4a0 ext4_init_new_dir+0x145/0x1d0 ext4_mkdir+0x326/0x920 vfs_mkdir+0x45c/0x740 do_mkdirat+0x234/0x2f0 __x64_sys_mkdir+0xd6/0x120 do_syscall_64+0x5f/0xfa0 entry_SYSCALL_64_after_hwframe+0x76/0x7e
The above issue occurs with us in errors=continue mode when accompanied by storage failures. There have been many inconsistencies in the file system data. In the case of file system data inconsistency, for example, if the block bitmap of a referenced block is not set, it can lead to the situation where a block being committed is allocated and used again. As a result, the following condition will not be satisfied then trigger BUG_ON. Of course, it is entirely possible to construct a problematic image that can trigger this BUG_ON through specific operations. In fact, I have constructed such an image and easily reproduced this issue. Therefore, J_ASSERT() holds true only under ideal conditions, but it may not necessarily be satisfied in exceptional scenarios. Using J_ASSERT() directly in abnormal situations would cause the system to crash, which is clearly not what we want. So here we directly trigger a JBD abort instead of immediately invoking BUG_ON.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
A BUG_ON crash in the Linux kernel's jbd2 journaling layer can be triggered by filesystem corruption, allowing denial of service.
Vulnerability
CVE-2025-68337 is a denial-of-service vulnerability in the Linux kernel's jbd2 journaling subsystem, specifically in the jbd2_journal_get_create_access() function. The root cause is the use of a BUG_ON assertion (converted from J_ASSERT) that assumes ideal filesystem consistency. When the filesystem metadata is corrupted—for example, if a block bitmap is not set for a referenced block—a block being committed can be allocated and reused, causing the assertion to fail and triggering a kernel panic [1].
Exploitation
An attacker with the ability to corrupt a mounted ext4 filesystem (e.g., through storage failures or by crafting a malicious disk image) can trigger this bug. The corruption leads to inconsistencies such as an unset block bitmap for a referenced block. When a user-space operation like mkdir calls into ext4_init_new_dir, which eventually reaches jbd2_journal_get_create_access(), the invalid state causes the BUG_ON` to fire, crashing the system. No authentication is required beyond access to the filesystem, and the attack can be carried out remotely if the filesystem is shared over a network [1].
Impact
Successful exploitation results in a kernel panic (Oops), causing a denial of service for the affected system. The crash is immediate and does not require any special privileges beyond the ability to trigger filesystem operations on a corrupted volume. The vulnerability is particularly dangerous in environments using errors=continue mode, where the kernel attempts to proceed despite corruption, increasing the likelihood of hitting this assertion [1].
Mitigation
The fix replaces the BUG_ON with a more graceful error handling path, allowing the journaling layer to recover or return an error instead of crashing. The fix has been backported to multiple stable kernel trees [2][3][4]. Users should apply the latest kernel updates from their distribution to remediate this issue.
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
1Patches
0No patches discovered yet.
Vulnerability mechanics
AI mechanics synthesis has not run for this CVE yet.
References
8- git.kernel.org/stable/c/3faac6531d4818cd6be45e5bbf32937bbbc795c0nvd
- git.kernel.org/stable/c/71bbe06c40fc59b5b15661eca8ff307f4176d7f9nvd
- git.kernel.org/stable/c/986835bf4d11032bba4ab8414d18fce038c61bb4nvd
- git.kernel.org/stable/c/a2a7f854d154a3e9232fec80782dad951655f52fnvd
- git.kernel.org/stable/c/aa1703f3f706ea0867fb1991dcac709c9ec94cfbnvd
- git.kernel.org/stable/c/b4f8eabf6d991bd41fabcdf9302c4b3eab590cf4nvd
- git.kernel.org/stable/c/bf34c72337e40c4670cceeb79b353356933a254bnvd
- git.kernel.org/stable/c/ed62fd8c15d41c4127ad16b8219b63124f5962bcnvd
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