dm cache：修复第一次恢复时可能出现的越界访问（CVE-2024-50278）
CVE编号
CVE-2024-50278
利用情况
暂无
补丁情况
N/A
披露时间
2024-11-19
漏洞描述
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:
1. prepare component devices:
dmsetup create cmeta --table "0 8192 linear /dev/sdc 0"
dmsetup create cdata --table "0 65536 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
2. 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 "0 524288 cache /dev/mapper/cmeta \
/dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0"
dmsetup reload cdata --table "0 131072 linear /dev/sdc 8192"
dmsetup resume cdata
dmsetup resume cache
3. 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.
解决建议
建议您更新当前系统或软件至最新版，完成漏洞的修复。
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