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Message-ID: <2024122731-CVE-2024-56631-548f@gregkh> Date: Fri, 27 Dec 2024 16:02:32 +0100 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-cve-announce@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org> Subject: CVE-2024-56631: scsi: sg: Fix slab-use-after-free read in sg_release() Description =========== 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(). The Linux kernel CVE team has assigned CVE-2024-56631 to this issue. Affected and fixed versions =========================== Issue introduced in 3.17 with commit cc833acbee9db5ca8c6162b015b4c93863c6f821 and fixed in 6.6.66 with commit 59b30afa578637169e2819536bb66459fdddc39d Issue introduced in 3.17 with commit cc833acbee9db5ca8c6162b015b4c93863c6f821 and fixed in 6.12.5 with commit 1f5e2f1ca5875728fcf62bc1a054707444ab4960 Issue introduced in 3.17 with commit cc833acbee9db5ca8c6162b015b4c93863c6f821 and fixed in 6.13-rc2 with commit f10593ad9bc36921f623361c9e3dd96bd52d85ee Issue introduced in 3.16.85 with commit 3a27c0defb0315760100f8b1adc7c4acbe04c884 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2024-56631 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: drivers/scsi/sg.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/59b30afa578637169e2819536bb66459fdddc39d https://git.kernel.org/stable/c/1f5e2f1ca5875728fcf62bc1a054707444ab4960 https://git.kernel.org/stable/c/f10593ad9bc36921f623361c9e3dd96bd52d85ee
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