CVE-2024-39276: ext4: fix mb_cache_entry's e_refcnt leak in ext4_xattr_block_cache_find()
First published: Tue Jun 25 2024(Updated: )
In the Linux kernel, the following vulnerability has been resolved: ext4: fix mb_cache_entry's e_refcnt leak in ext4_xattr_block_cache_find() Syzbot reports a warning as follows: ============================================ WARNING: CPU: 0 PID: 5075 at fs/mbcache.c:419 mb_cache_destroy+0x224/0x290 Modules linked in: CPU: 0 PID: 5075 Comm: syz-executor199 Not tainted 6.9.0-rc6-gb947cc5bf6d7 RIP: 0010:mb_cache_destroy+0x224/0x290 fs/mbcache.c:419 Call Trace: <TASK> ext4_put_super+0x6d4/0xcd0 fs/ext4/super.c:1375 generic_shutdown_super+0x136/0x2d0 fs/super.c:641 kill_block_super+0x44/0x90 fs/super.c:1675 ext4_kill_sb+0x68/0xa0 fs/ext4/super.c:7327 [...] ============================================ This is because when finding an entry in ext4_xattr_block_cache_find(), if ext4_sb_bread() returns -ENOMEM, the ce's e_refcnt, which has already grown in the __entry_find(), won't be put away, and eventually trigger the above issue in mb_cache_destroy() due to reference count leakage. So call mb_cache_entry_put() on the -ENOMEM error branch as a quick fix.
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| redhat/kernel | <4.19.316 | 4.19.316 |
| redhat/kernel | <5.4.278 | 5.4.278 |
| redhat/kernel | <5.10.219 | 5.10.219 |
| redhat/kernel | <5.15.161 | 5.15.161 |
| redhat/kernel | <6.1.94 | 6.1.94 |
| redhat/kernel | <6.6.34 | 6.6.34 |
| redhat/kernel | <6.9.5 | 6.9.5 |
| redhat/kernel | <6.10 | 6.10 |
| debian/linux | 5.10.223-1 5.10.234-1 6.1.123-1 6.1.128-1 6.12.12-1 6.12.16-1 |
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Reference Links
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-39276
- https://nvd.nist.gov/vuln/detail/CVE-2024-39276
- https://launchpad.net/bugs/cve/CVE-2024-39276
- https://security-tracker.debian.org/tracker/CVE-2024-39276
- https://ubuntu.com/security/CVE-2024-39276
- https://git.kernel.org/stable/c/0c0b4a49d3e7f49690a6827a41faeffad5df7e21
- https://git.kernel.org/stable/c/681ff9a09accd8a4379f8bd30b7a1641ee19bb3e
- https://git.kernel.org/stable/c/76dc776153a47372719d664e0fc50d6355791abb
- https://git.kernel.org/stable/c/896a7e7d0d555ad8b2b46af0c2fa7de7467f9483
- https://git.kernel.org/stable/c/9ad75e78747b5a50dc5a52f0f8e92e920a653f16
- https://git.kernel.org/stable/c/a95df6f04f2c37291adf26a74205cde0314d4577
- https://git.kernel.org/stable/c/b37c0edef4e66fb21a2fbc211471195a383e5ab8
- https://git.kernel.org/stable/c/e941b712e758f615d311946bf98216e79145ccd9
- https://git.kernel.org/linus/0c0b4a49d3e7f49690a6827a41faeffad5df7e21
- https://access.redhat.com/security/cve/CVE-2024-39276
- https://lore.kernel.org/linux-cve-announce/2024062548-CVE-2024-39276-5205@gregkh/T
- https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=2294276
- https://access.redhat.com/errata/RHSA-2024:5102
- https://access.redhat.com/errata/RHSA-2024:5101
- https://access.redhat.com/errata/RHSA-2024:9315
- https://bugzilla.redhat.com/show_bug.cgi?id=2294274
Frequently Asked Questions
What is the severity of CVE-2024-39276?
CVE-2024-39276 is classified as a medium severity vulnerability in the Linux kernel due to the potential for an e_refcnt leak.
How do I fix CVE-2024-39276?
To fix CVE-2024-39276, upgrade to the recommended versions of the Linux kernel which include patches for this vulnerability.
What systems are affected by CVE-2024-39276?
CVE-2024-39276 affects various versions of the Linux kernel including specific versions from Red Hat and Debian distributions.
Is there a workaround for CVE-2024-39276?
There are no known workarounds for CVE-2024-39276; the recommended action is to apply the kernel updates provided.
What are the impacts of CVE-2024-39276 if left unpatched?
If left unpatched, CVE-2024-39276 could potentially lead to data integrity issues due to the e_refcnt leak in the ext4 file system.
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