CVE-2024-50279

Summary

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

dm cache: fix out-of-bounds access to the dirty bitset when resizing

dm-cache checks the dirty bits of the cache blocks to be dropped when shrinking the fast device, but an index bug in bitset iteration causes out-of-bounds access.

Reproduce steps:

1. create a cache device of 1024 cache blocks (128 bytes dirty bitset)

dmsetup create cmeta –table "0 8192 linear /dev/sdc 0" dmsetup create cdata –table "0 131072 linear /dev/sdc 8192" dmsetup create corig –table "0 524288 linear /dev/sdc 262144" dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 oflag=direct dmsetup create cache –table "0 524288 cache /dev/mapper/cmeta
/dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0"

2. shrink the fast device to 512 cache blocks, triggering out-of-bounds access to the dirty bitset (offset 0x80)

dmsetup suspend cache dmsetup reload cdata –table "0 65536 linear /dev/sdc 8192" dmsetup resume cdata dmsetup resume cache

KASAN reports:

BUG: KASAN: vmalloc-out-of-bounds in cache_preresume+0x269/0x7b0 Read of size 8 at addr ffffc900000f3080 by task dmsetup/131

(…snip…) The buggy address belongs to the virtual mapping at [ffffc900000f3000, ffffc900000f5000) created by: cache_ctr+0x176a/0x35f0

(…snip…) Memory state around the buggy address: ffffc900000f2f80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ffffc900000f3000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >ffffc900000f3080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ^ ffffc900000f3100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ffffc900000f3180: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8

Fix by making the index post-incremented.

Affected Software

Weaknesses

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: no
  • Technical Impact: partial

CVE Program Container

Additional References

• https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html
• https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html

References

• https://git.kernel.org/stable/c/4fa4feb873cea0e9d6ff883b37cca6f33169d8b4
• https://git.kernel.org/stable/c/8501e38dc9e0060814c4085815fc83da3e6d43bf
• https://git.kernel.org/stable/c/ee1f74925717ab36f6a091104c170639501ce818
• https://git.kernel.org/stable/c/ff1dd8a04c30e8d4e2fd5c83198ca672eb6a9e7f
• https://git.kernel.org/stable/c/56507203e1b6127967ec2b51fb0b23a0d4af1334
• https://git.kernel.org/stable/c/e57648ce325fa405fe6bbd0e6a618ced7c301a2d
• https://git.kernel.org/stable/c/3b02c40ff10fdf83cc545850db208de855ebe22c
• https://git.kernel.org/stable/c/792227719725497ce10a8039803bec13f89f8910

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