CVE-2024-50279

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> dm cache: fix out-of-bounds access to the dirty bitset when resizing<br /> <br /> dm-cache checks the dirty bits of the cache blocks to be dropped when<br /> shrinking the fast device, but an index bug in bitset iteration causes<br /> out-of-bounds access.<br /> <br /> Reproduce steps:<br /> <br /> 1. create a cache device of 1024 cache blocks (128 bytes dirty bitset)<br /> <br /> dmsetup create cmeta --table "0 8192 linear /dev/sdc 0"<br /> dmsetup create cdata --table "0 131072 linear /dev/sdc 8192"<br /> dmsetup create corig --table "0 524288 linear /dev/sdc 262144"<br /> dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 oflag=direct<br /> dmsetup create cache --table "0 524288 cache /dev/mapper/cmeta \<br /> /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0"<br /> <br /> 2. shrink the fast device to 512 cache blocks, triggering out-of-bounds<br /> access to the dirty bitset (offset 0x80)<br /> <br /> dmsetup suspend cache<br /> dmsetup reload cdata --table "0 65536 linear /dev/sdc 8192"<br /> dmsetup resume cdata<br /> dmsetup resume cache<br /> <br /> KASAN reports:<br /> <br /> BUG: KASAN: vmalloc-out-of-bounds in cache_preresume+0x269/0x7b0<br /> Read of size 8 at addr ffffc900000f3080 by task dmsetup/131<br /> <br /> (...snip...)<br /> The buggy address belongs to the virtual mapping at<br /> [ffffc900000f3000, ffffc900000f5000) created by:<br /> cache_ctr+0x176a/0x35f0<br /> <br /> (...snip...)<br /> Memory state around the buggy address:<br /> ffffc900000f2f80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8<br /> ffffc900000f3000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00<br /> &gt;ffffc900000f3080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8<br /> ^<br /> ffffc900000f3100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8<br /> ffffc900000f3180: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8<br /> <br /> Fix by making the index post-incremented.