On Thu, Jun 15, 2023 at 12:27:53AM +0100, David Howells wrote: > > If an AF_ALG socket bound to a hashing algorithm is sent a zero-length > message with MSG_MORE set and then recvmsg() is called without first > sending another message without MSG_MORE set to end the operation, an oops > will occur because the crypto context and result doesn't now get set up in > advance because hash_sendmsg() now defers that as long as possible in the > hope that it can use crypto_ahash_digest() - and then because the message > is zero-length, it the data wrangling loop is skipped. > > Fix this by always making a pass of the loop, even in the case that no data > is provided to the sendmsg(). > > Fix also extract_iter_to_sg() to handle a zero-length iterator by returning > 0 immediately. > > Whilst we're at it, remove the code to create a kvmalloc'd scatterlist if > we get more than ALG_MAX_PAGES - this shouldn't happen. I don't think this is right. If it's a zero-length message with MSG_MORE set, it should be ignored until a recvmsg(2) call is made. In any case, this patch doesn't fix all the syzbot reports. We need to think about reverting this change if it can't be fixed in time. Thanks, -- Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
