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The vulnerability exists within the `jbd2_journal_dirty_metadata()` function in the Linux kernel’s filesystem journaling layer. This function is critical for ensuring metadata consistency in the ext4 filesystem. A NULL pointer dereference occurs when the code attempts to access `handle->h_transaction` without verifying the handle’s state. If `handle` is aborted, `h_transaction` can be NULL, leading to a kernel oops or panic. Concurrently, a data-race condition exists on the `jh->b_modified` flag due to missing access synchronization annotations. This race was identified by the Kernel Concurrency Sanitizer (KCSAN), reporting concurrent reads and writes by different tasks. The unsynchronized access to `jh->b_modified` can corrupt journal state information. This corruption may lead to filesystem inconsistencies or crashes when journal entries are processed. The null-pointer dereference provides a direct path for a denial-of-service attack. The data-race, while more subtle, can destabilize the journaling mechanism over time. Both issues stem from insufficient validation and missing memory barrier protections in a core kernel function.
Platform: Linux kernel
Version: multiple versions
Vulnerability: data-race null-ptr-deref
Severity: medium
date: 07/10/2025
Prediction: Patch date: 2025-07-10
What Undercode Say:
Analytics:
`uname -r`
`lsmod | grep jbd2`
`grep -n “jbd2_journal_dirty_metadata” /usr/src/linux-source-/fs/jbd2/transaction.c`
`cat /proc/sys/kernel/tainted`
`dmesg | grep “KCSAN”`
// Code snippet from fs/jbd2/transaction.c around line 1556
`if (is_handle_aborted(handle))`
` return -EROFS;`
`read_seqlock_excl(&journal->j_state_lock);`
`jh->b_modified = 1;`
how Exploit:
Trigger handle abort.
Concurrent metadata operations.
Kernel pointer dereference.
Protection from this CVE
Update kernel version.
Apply security patches.
Disable vulnerable features.
Impact:
Kernel panic.
Filesystem corruption.
Privilege escalation.
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Sources:
Reported By: nvd.nist.gov
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