2.3 KiB
CVE-2024-50279
Description
In the Linux kernel, the following vulnerability has been resolved:dm cache: fix out-of-bounds access to the dirty bitset when resizingdm-cache checks the dirty bits of the cache blocks to be dropped whenshrinking the fast device, but an index bug in bitset iteration causesout-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=directdmsetup 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 cachedmsetup reload cdata --table "0 65536 linear /dev/sdc 8192"dmsetup resume cdatadmsetup resume cacheKASAN 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 f8Fix by making the index post-incremented.
POC
Reference
No PoCs from references.