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Improper Input Validation Affecting kernel-livepatch-6.1.79-99.164 package, versions <0:1.0-0.amzn2023

Severity

 Recommended
high

Based on Amazon Linux security rating.

Threat Intelligence

EPSS
0.04% (12th percentile)

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  • Snyk IDSNYK-AMZN2023-KERNELLIVEPATCH617999164-7708377
  • published20 Aug 2024
  • disclosed3 Apr 2024
Report a new vulnerability Found a mistake?

Introduced: 3 Apr 2024

CVE-2024-26727  (opens in a new tab)
CWE-20  (opens in a new tab)

How to fix?

Upgrade Amazon-Linux:2023 kernel-livepatch-6.1.79-99.164 to version 0:1.0-0.amzn2023 or higher.
This issue was patched in ALAS2023-2024-549.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-livepatch-6.1.79-99.164 package and not the kernel-livepatch-6.1.79-99.164 package as distributed by Amazon-Linux. See How to fix? for Amazon-Linux:2023 relevant fixed versions and status.

In the Linux kernel, the following vulnerability has been resolved:

btrfs: do not ASSERT() if the newly created subvolume already got read

[BUG] There is a syzbot crash, triggered by the ASSERT() during subvolume creation:

assertion failed: !anon_dev, in fs/btrfs/disk-io.c:1319 ------------[ cut here ]------------ kernel BUG at fs/btrfs/disk-io.c:1319! invalid opcode: 0000 [#1] PREEMPT SMP KASAN RIP: 0010:btrfs_get_root_ref.part.0+0x9aa/0xa60 <TASK> btrfs_get_new_fs_root+0xd3/0xf0 create_subvol+0xd02/0x1650 btrfs_mksubvol+0xe95/0x12b0 __btrfs_ioctl_snap_create+0x2f9/0x4f0 btrfs_ioctl_snap_create+0x16b/0x200 btrfs_ioctl+0x35f0/0x5cf0 __x64_sys_ioctl+0x19d/0x210 do_syscall_64+0x3f/0xe0 entry_SYSCALL_64_after_hwframe+0x63/0x6b ---[ end trace 0000000000000000 ]---

[CAUSE] During create_subvol(), after inserting root item for the newly created subvolume, we would trigger btrfs_get_new_fs_root() to get the btrfs_root of that subvolume.

The idea here is, we have preallocated an anonymous device number for the subvolume, thus we can assign it to the new subvolume.

But there is really nothing preventing things like backref walk to read the new subvolume. If that happens before we call btrfs_get_new_fs_root(), the subvolume would be read out, with a new anonymous device number assigned already.

In that case, we would trigger ASSERT(), as we really expect no one to read out that subvolume (which is not yet accessible from the fs). But things like backref walk is still possible to trigger the read on the subvolume.

Thus our assumption on the ASSERT() is not correct in the first place.

[FIX] Fix it by removing the ASSERT(), and just free the @anon_dev, reset it to 0, and continue.

If the subvolume tree is read out by something else, it should have already get a new anon_dev assigned thus we only need to free the preallocated one.

CVSS Scores

version 3.1