1. 02 Feb, 2024 1 commit
    • Mikulas Patocka's avatar
      dm-crypt, dm-verity: disable tasklets · 0a9bab39
      Mikulas Patocka authored
      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 8e14f610 and d9a02e01 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/d390d7ee-f142-44d3-822a-87949e14608b@suse.de/T/
      [2] https://lore.kernel.org/lkml/20240130091300.2968534-1-tj@kernel.org/Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
      Cc: stable@vger.kernel.org
      Fixes: 39d42fa9 ("dm crypt: add flags to optionally bypass kcryptd workqueues")
      Fixes: 5721d4e5 ("dm verity: Add optional "try_verify_in_tasklet" feature")
      Signed-off-by: default avatarMike Snitzer <snitzer@kernel.org>
      0a9bab39
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