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crypto: api - Check spawn->alg under lock in crypto_drop_spawn

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commit 7db3b61b6bba4310f454588c2ca6faf2958ad79f upstream.

We need to check whether spawn->alg is NULL under lock as otherwise
the algorithm could be removed from under us after we have checked
it and found it to be non-NULL.  This could cause us to remove the
spawn from a non-existent list.

Fixes: 7ede5a5ba5 ("crypto: api - Fix crypto_drop_spawn crash...")
Cc: <stable@vger.kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Herbert Xu 2019-12-06 13:55:17 +08:00 committed by Greg Kroah-Hartman
parent f3f9cfca05
commit 12fa296ad2
1 changed files with 2 additions and 4 deletions
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6
crypto/algapi.c
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@ -649,11 +649,9 @@ EXPORT_SYMBOL_GPL(crypto_grab_spawn);
void crypto_drop_spawn(struct crypto_spawn *spawn)
{
if (!spawn->alg)
return;
down_write(&crypto_alg_sem);
list_del(&spawn->list);
if (spawn->alg)
list_del(&spawn->list);
up_write(&crypto_alg_sem);
}
EXPORT_SYMBOL_GPL(crypto_drop_spawn);