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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: <stable@vger.kernel.org> Signed-off-by: Stephan Mueller <smueller@chronox.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.