CVE-2024-26718

In the Linux kernel, the following vulnerability has been resolved:

dm-crypt, dm-verity: disable tasklets

Tasklets have an inherent problem with memory corruption. The function

tasklet_action_common calls tasklet_trylock, then it calls the tasklet

callback and then it calls tasklet_unlock. If the tasklet callback frees

the structure that contains the tasklet or if it calls some code that may

free it, tasklet_unlock will write into free memory.

The commits 8e14f610159d and d9a02e016aaf try to fix it for dm-crypt, but

it is not a sufficient fix and the data corruption can still happen [1].

There is no fix for dm-verity and dm-verity will write into free memory

with every tasklet-processed bio.

There will be atomic workqueues implemented in the kernel 6.9 [2]. They

will have better interface and they will not suffer from the memory

corruption problem.

But we need something that stops the memory corruption now and that can be

backported to the stable kernels. So, I'm proposing this commit that

disables tasklets in both dm-crypt and dm-verity. This commit doesn't

remove the tasklet support, because the tasklet code will be reused when

atomic workqueues will be implemented.

[1] https://lore.kernel.org/all/[email protected]/T/

[2] https://lore.kernel.org/lkml/[email protected]/