crypto: api - check for ERR pointers in crypto_destroy_tfm()

[ Upstream commit 83681f2bebb34dbb3f03fecd8f570308ab8b7c2c ]

Given that crypto_alloc_tfm() may return ERR pointers, and to avoid
crashes on obscure error paths where such pointers are presented to
crypto_destroy_tfm() (such as [0]), add an ERR_PTR check there
before dereferencing the second argument as a struct crypto_tfm
pointer.

[0] https://lore.kernel.org/linux-crypto/000000000000de949705bc59e0f6@google.com/

Reported-by: syzbot+12cf5fbfdeba210a89dd@syzkaller.appspotmail.com
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>

include/crypto/akcipher.h

@@ -174,6 +174,8 @@ static inline struct crypto_akcipher *crypto_akcipher_reqtfm(
  * crypto_free_akcipher() - free AKCIPHER tfm handle
  *
  * @tfm: AKCIPHER tfm handle allocated with crypto_alloc_akcipher()
+ *
+ * If @tfm is a NULL or error pointer, this function does nothing.
  */
 static inline void crypto_free_akcipher(struct crypto_akcipher *tfm)
 {