CVE-2024-50279 Information

Nov 20, 2024 cve

Description

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:

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

dmsetup create cmeta –table �8192 linear /dev/sdc 0\ndmsetup create cdata –table 1072 linear /dev/sdc 8192\ndmsetup create corig –table *4288 linear /dev/sdc 262144\ndd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 oflag=direct dmsetup create cache –table *4288 cache /dev/mapper/cmeta
/dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0\n 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 5536 linear /dev/sdc 8192\ndmsetup 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.

Reference

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