CVE-2026-53064

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> dm cache: fix null-deref with concurrent writes in passthrough mode<br /> <br /> In passthrough mode, when dm-cache starts to invalidate a cache<br /> entry and bio prison cell lock fails due to concurrent write to<br /> the same cached block, mg-&gt;cell remains NULL. The error path in<br /> invalidate_complete() attempts to unlock and free the cell<br /> unconditionally, causing a NULL pointer dereference:<br /> <br /> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]<br /> CPU: 0 UID: 0 PID: 134 Comm: fio Not tainted 6.19.0-rc7 #3 PREEMPT<br /> RIP: 0010:dm_cell_unlock_v2+0x3f/0x210<br /> <br /> Call Trace:<br /> invalidate_complete+0xef/0x430<br /> map_bio+0x130f/0x1a10<br /> cache_map+0x320/0x6b0<br /> __map_bio+0x458/0x510<br /> dm_submit_bio+0x40e/0x16d0<br /> __submit_bio+0x419/0x870<br /> <br /> <br /> Reproduce steps:<br /> <br /> 1. Create a cache device<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 262144 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 262144 cache /dev/mapper/cmeta \<br /> /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0"<br /> <br /> 2. Promote the first data block into cache<br /> <br /> fio --filename=/dev/mapper/cache --name=populate --rw=write --bs=4k \<br /> --direct=1 --size=64k<br /> <br /> 3. Reload the cache into passthrough mode<br /> <br /> dmsetup suspend cache<br /> dmsetup reload cache --table "0 262144 cache /dev/mapper/cmeta \<br /> /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 passthrough smq 0"<br /> dmsetup resume cache<br /> <br /> 4. Write to the first cached block concurrently<br /> <br /> fio --filename=/dev/mapper/cache --name test --rw=randwrite --bs=4k \<br /> --randrepeat=0 --direct=1 --numjobs=2 --size 64k<br /> <br /> Fix by checking if mg-&gt;cell is valid before attempting to unlock it.