CVE-2024-50278

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> dm cache: fix potential out-of-bounds access on the first resume<br /> <br /> Out-of-bounds access occurs if the fast device is expanded unexpectedly<br /> before the first-time resume of the cache table. This happens because<br /> expanding the fast device requires reloading the cache table for<br /> cache_create to allocate new in-core data structures that fit the new<br /> size, and the check in cache_preresume is not performed during the<br /> first resume, leading to the issue.<br /> <br /> Reproduce steps:<br /> <br /> 1. prepare component devices:<br /> <br /> dmsetup create cmeta --table "0 8192 linear /dev/sdc 0"<br /> dmsetup create cdata --table "0 65536 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 /> <br /> 2. load a cache table of 512 cache blocks, and deliberately expand the<br /> fast device before resuming the cache, making the in-core data<br /> structures inadequate.<br /> <br /> dmsetup create cache --notable<br /> dmsetup reload cache --table "0 524288 cache /dev/mapper/cmeta \<br /> /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0"<br /> dmsetup reload cdata --table "0 131072 linear /dev/sdc 8192"<br /> dmsetup resume cdata<br /> dmsetup resume cache<br /> <br /> 3. suspend the cache to write out the in-core dirty bitset and hint<br /> array, leading to out-of-bounds access to the dirty bitset at offset<br /> 0x40:<br /> <br /> dmsetup suspend cache<br /> <br /> KASAN reports:<br /> <br /> BUG: KASAN: vmalloc-out-of-bounds in is_dirty_callback+0x2b/0x80<br /> Read of size 8 at addr ffffc90000085040 by task dmsetup/90<br /> <br /> (...snip...)<br /> The buggy address belongs to the virtual mapping at<br /> [ffffc90000085000, ffffc90000087000) created by:<br /> cache_ctr+0x176a/0x35f0<br /> <br /> (...snip...)<br /> Memory state around the buggy address:<br /> ffffc90000084f00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8<br /> ffffc90000084f80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8<br /> &gt;ffffc90000085000: 00 00 00 00 00 00 00 00 f8 f8 f8 f8 f8 f8 f8 f8<br /> ^<br /> ffffc90000085080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8<br /> ffffc90000085100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8<br /> <br /> Fix by checking the size change on the first resume.