Re: [PATCH v2] crypto: AES-NI GCM - handle zero length dst buffer

On Thu, Jan 18, 2018 at 08:41:09PM +0100, Stephan Müller wrote:

Hi Herbert,

Sorry, I forgot to CC you on this patch -- v2 is unchanged from the
original patch. It only adds you in copy.

---8<---

GCM can be invoked with a zero destination buffer. This is possible if
the AAD and the ciphertext have zero lengths and only the tag exists in
the source buffer (i.e. a source buffer cannot be zero). In this case,
the GCM cipher only performs the authentication and no decryption
operation.

When the destination buffer has zero length, it is possible that no page
is mapped to the SG pointing to the destination. In this case,
sg_page(req->dst) is an invalid access. Therefore, page accesses should
only be allowed if the req->dst->length is non-zero which is the
indicator that a page must exist.

This fixes a crash that can be triggered by user space via AF_ALG.

CC: <redacted>
Signed-off-by: Stephan Mueller <redacted>

Patch applied.  Thanks.
-- 
Email: Herbert Xu [off-list ref]
Home Page: http://gondor.apana.org.au/~herbert/
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