crypto: shash - Fix a sleep-in-atomic bug in shash_setkey_unaligned

The SCTP program may sleep under a spinlock, and the function call path is:
sctp_generate_t3_rtx_event (acquire the spinlock)
  sctp_do_sm
    sctp_side_effects
      sctp_cmd_interpreter
        sctp_make_init_ack
          sctp_pack_cookie
            crypto_shash_setkey
              shash_setkey_unaligned
                kmalloc(GFP_KERNEL)

For the same reason, the orinoco driver may sleep in interrupt handler,
and the function call path is:
orinoco_rx_isr_tasklet
  orinoco_rx
    orinoco_mic
      crypto_shash_setkey
        shash_setkey_unaligned
          kmalloc(GFP_KERNEL)

To fix it, GFP_KERNEL is replaced with GFP_ATOMIC.
This bug is found by my static analysis tool and my code review.

Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/shash.c

@@ -41,7 +41,7 @@ static int shash_setkey_unaligned(struct crypto_shash *tfm, const u8 *key,
 	int err;
 
 	absize = keylen + (alignmask & ~(crypto_tfm_ctx_alignment() - 1));
-	buffer = kmalloc(absize, GFP_KERNEL);
+	buffer = kmalloc(absize, GFP_ATOMIC);
 	if (!buffer)
 		return -ENOMEM;