CVE-2024-50278 Information

Nov 20, 2024 cve

Description

In the Linux kernel the following vulnerability has been resolved:

dm cache: fix potential out-of-bounds access on the first resume

Out-of-bounds access occurs if the fast device is expanded unexpectedly before the first-time resume of the cache table. This happens because expanding the fast device requires reloading the cache table for cache_create to allocate new in-core data structures that fit the new size and the check in cache_preresume is not performed during the first resume leading to the issue.

Reproduce steps:

prepare component devices:

dmsetup create cmeta –table �8192 linear /dev/sdc 0\ndmsetup create cdata –table 5536 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

load a cache table of 512 cache blocks and deliberately expand the fast device before resuming the cache making the in-core data structures inadequate.

dmsetup create cache –notable dmsetup reload cache –table *4288 cache /dev/mapper/cmeta
/dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0\ndmsetup reload cdata –table 1072 linear /dev/sdc 8192\ndmsetup resume cdata dmsetup resume cache

suspend the cache to write out the in-core dirty bitset and hint array leading to out-of-bounds access to the dirty bitset at offset 0x40:

dmsetup suspend cache

KASAN reports:

BUG: KASAN: vmalloc-out-of-bounds in is_dirty_callback+0x2b/0x80 Read of size 8 at addr ffffc90000085040 by task dmsetup/90

(…snip…) The buggy address belongs to the virtual mapping at [ffffc90000085000 ffffc90000087000) created by: cache_ctr+0x176a/0x35f0

(…snip…) Memory state around the buggy address: ffffc90000084f00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ffffc90000084f80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8

ffffc90000085000: 00 00 00 00 00 00 00 00 f8 f8 f8 f8 f8 f8 f8 f8 ^ ffffc90000085080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ffffc90000085100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8

Fix by checking the size change on the first resume.

Reference

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