crypto: shash - Fix zero-length shash ahash digest crash

The shash ahash digest adaptor function may crash if given a
zero-length input together with a null SG list.  This is because
it tries to read the SG list before looking at the length.

This patch fixes it by checking the length first.

Cc: <>
Reported-by: Stephan Müller<>
Signed-off-by: Herbert Xu <>
Tested-by: Stephan Müller <>
1 file changed