CVE-2024-49959 jbd2: stop waiting for space when jbd2_cleanup_journal_tail() returns error
A flaw in the Linux kernel's jbd2 journaling subsystem can cause a system hang or crash when journal cleanup fails, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-49959?
CVE-2024-49959 is a medium-severity denial of service vulnerability in Linux kernel, published on 21 Oct 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
jbd2: stop waiting for space when jbd2_cleanup_journal_tail() returns error
In __jbd2_log_wait_for_space(), we might call jbd2_cleanup_journal_tail() to recover some journal space. But if an error occurs while executing jbd2_cleanup_journal_tail() (e.g., an EIO), we don't stop waiting for free space right away, we try other branches, and if j_committing_transaction is NULL (i.e., the tid is 0), we will get the following complain:
============================================ JBD2: I/O error when updating journal superblock for sdd-8. __jbd2_log_wait_for_space: needed 256 blocks and only had 217 space available __jbd2_log_wait_for_space: no way to get more journal space in sdd-8 ------------[ cut here ]------------ WARNING: CPU: 2 PID: 139804 at fs/jbd2/checkpoint.c:109 __jbd2_log_wait_for_space+0x251/0x2e0 Modules linked in: CPU: 2 PID: 139804 Comm: kworker/u8:3 Not tainted 6.6.0+ #1 RIP: 0010:__jbd2_log_wait_for_space+0x251/0x2e0 Call Trace: <TASK> add_transaction_credits+0x5d1/0x5e0 start_this_handle+0x1ef/0x6a0 jbd2__journal_start+0x18b/0x340 ext4_dirty_inode+0x5d/0xb0 __mark_inode_dirty+0xe4/0x5d0 generic_update_time+0x60/0x70 [...] ============================================
So only if jbd2_cleanup_journal_tail() returns 1, i.e., there is nothing to clean up at the moment, continue to try to reclaim free space in other ways.
Note that this fix relies on commit 6f6a6fda2945 ("jbd2: fix ocfs2 corrupt when updating journal superblock fails") to make jbd2_cleanup_journal_tail return the correct error code.
Which versions are affected by CVE-2024-49959?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-49959?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2024-49959 being exploited?
There is no known exploitation of CVE-2024-49959 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-52296, BELL-CVE-2024-49959, DEBIAN-CVE-2024-49959, GHSA-q7pc-7wvx-9qcx, UBUNTU-CVE-2024-49959.