Re: [PATCH 1/2] dm verity: init fec io before cleaning it

[Eric Biggers <ebiggers@kernel.org>]

On Tue, Nov 21, 2023 at 01:55:28AM -0700, Wu Bo wrote:
> If BIO error, it may goto verity_finish_io() before
> verity_fec_init_io(). Therefor, the fec_io->rs is not initialized and
> may crash when doing memory freeing in verity_fec_finish_io().
> 
> Crash call stack:
>  die+0x90/0x2b8
>  __do_kernel_fault+0x260/0x298
>  do_bad_area+0x2c/0xdc
>  do_translation_fault+0x3c/0x54
>  do_mem_abort+0x54/0x118
>  el1_abort+0x38/0x5c
>  el1h_64_sync_handler+0x50/0x90
>  el1h_64_sync+0x64/0x6c
>  free_rs+0x18/0xac
>  fec_rs_free+0x10/0x24
>  mempool_free+0x58/0x148
>  verity_fec_finish_io+0x4c/0xb0
>  verity_end_io+0xb8/0x150
> 
> Signed-off-by: Wu Bo <bo.wu@vivo.com>

What commit introduced this bug?  It looks like it was commit 5721d4e5a9cd ("dm
verity: Add optional "try_verify_in_tasklet" feature"), which moved the call to
verity_fec_init_io() from verity_map() to verity_work().  Do you agree?  Should
the call to verity_fec_init_io() perhaps be moved back to verity_map(), instead
of putting it in verity_end_io()?  Or maybe another call to verity_fec_init_io()
should be added only just before the call to verity_finish_io() in
verity_end_io(), given that it's not needed in the tasklet case?

In any case, please also add a Fixes tag with the appropriate commit, as well as
a "Cc stable" tag.

- Eric