CVE-2024-56631: scsi: sg: Fix slab-use-after-free read in sg_release()
First published: Fri Dec 27 2024(Updated: )
In the Linux kernel, the following vulnerability has been resolved: scsi: sg: Fix slab-use-after-free read in sg_release() Fix a use-after-free bug in sg_release(), detected by syzbot with KASAN: BUG: KASAN: slab-use-after-free in lock_release+0x151/0xa30 kernel/locking/lockdep.c:5838 __mutex_unlock_slowpath+0xe2/0x750 kernel/locking/mutex.c:912 sg_release+0x1f4/0x2e0 drivers/scsi/sg.c:407 In sg_release(), the function kref_put(&sfp->f_ref, sg_remove_sfp) is called before releasing the open_rel_lock mutex. The kref_put() call may decrement the reference count of sfp to zero, triggering its cleanup through sg_remove_sfp(). This cleanup includes scheduling deferred work via sg_remove_sfp_usercontext(), which ultimately frees sfp. After kref_put(), sg_release() continues to unlock open_rel_lock and may reference sfp or sdp. If sfp has already been freed, this results in a slab-use-after-free error. Move the kref_put(&sfp->f_ref, sg_remove_sfp) call after unlocking the open_rel_lock mutex. This ensures: - No references to sfp or sdp occur after the reference count is decremented. - Cleanup functions such as sg_remove_sfp() and sg_remove_sfp_usercontext() can safely execute without impacting the mutex handling in sg_release(). The fix has been tested and validated by syzbot. This patch closes the bug reported at the following syzkaller link and ensures proper sequencing of resource cleanup and mutex operations, eliminating the risk of use-after-free errors in sg_release().
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Linux Kernel | >=3.16.85<6.6.66 | |
| Linux Kernel | >=6.7<6.12.5 | |
| Linux Kernel | =6.13-rc1 | |
| debian/linux | <=5.10.223-1 | 5.10.234-1 6.1.129-1 6.1.128-1 6.12.20-1 6.12.21-1 |
| debian/linux-6.1 | 6.1.129-1~deb11u1 |
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Reference Links
- https://git.kernel.org/stable/c/e19acb1926c4a1f30ee1ec84d8afba2d975bd534
- https://git.kernel.org/stable/c/285ce1f89f8d414e7eecab5ef5118cd512596318
- https://git.kernel.org/stable/c/198b89dd5a595ee3f96e5ce5c448b0484cd0e53c
- https://git.kernel.org/stable/c/275b8347e21ab8193e93223a8394a806e4ba8918
- https://git.kernel.org/stable/c/59b30afa578637169e2819536bb66459fdddc39d
- https://git.kernel.org/stable/c/1f5e2f1ca5875728fcf62bc1a054707444ab4960
- https://git.kernel.org/stable/c/f10593ad9bc36921f623361c9e3dd96bd52d85ee
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-56631
- https://nvd.nist.gov/vuln/detail/CVE-2024-56631
- https://launchpad.net/bugs/cve/CVE-2024-56631
- https://security-tracker.debian.org/tracker/CVE-2024-56631
- https://ubuntu.com/security/CVE-2024-56631
- https://git.kernel.org/linus/f10593ad9bc36921f623361c9e3dd96bd52d85ee
Frequently Asked Questions
What is the severity of CVE-2024-56631?
CVE-2024-56631 has a medium severity rating due to its potential to cause a use-after-free condition in the Linux kernel.
How do I fix CVE-2024-56631?
To fix CVE-2024-56631, upgrade your Linux kernel to a version that includes the patch for this vulnerability.
Which Linux kernel versions are affected by CVE-2024-56631?
CVE-2024-56631 affects Linux kernel versions from 3.16.85 to 6.6.66 and versions between 6.7 and 6.12.5.
What causes the CVE-2024-56631 vulnerability?
CVE-2024-56631 is caused by a use-after-free bug in the sg_release() function in the Linux kernel.
Is CVE-2024-56631 detectable by security tools?
Yes, CVE-2024-56631 can be detected by security tools that utilize Kernel Address Sanitizer (KASAN) during their testing processes.
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