Re: [v2 PATCH] crc-t10dif: Fix potential crypto notify dead-lock

[Eric Biggers <ebiggers@kernel.org>]

On Fri, Jun 05, 2020 at 04:59:18PM +1000, Herbert Xu wrote:
> The crypto notify call occurs with a read mutex held so you must
> not do any substantial work directly.  In particular, you cannot
> call crypto_alloc_* as they may trigger further notifications
> which may dead-lock in the presence of another writer.
> 
> This patch fixes this by postponing the work into a work queue and
> taking the same lock in the module init function.
> 
> While we're at it this patch also ensures that all RCU accesses are
> marked appropriately (tested with sparse).
> 
> Finally this also reveals a race condition in module param show
> function as it may be called prior to the module init function.
> It's fixed by testing whether crct10dif_tfm is NULL (this is true
> iff the init function has not completed assuming fallback is false).
> 
> Fixes: 11dcb1037f40 ("crc-t10dif: Allow current transform to be...")
> Fixes: b76377543b73 ("crc-t10dif: Pick better transform if one...")
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Reviewed-by: Eric Biggers <ebiggers@google.com>

- Eric