On Mon, Nov 07, 2016 at 07:08:22PM +0100, Jason A. Donenfeld wrote: > Hmm... The general data flow that strikes me as most pertinent is > something like: > > struct sk_buff *skb = get_it_from_somewhere(); > skb = skb_share_check(skb, GFP_ATOMIC); > num_frags = skb_cow_data(skb, ..., ...); > struct scatterlist sg[num_frags]; > sg_init_table(sg, num_frags); > skb_to_sgvec(skb, sg, ..., ...); > blkcipher_walk_init(&walk, sg, sg, len); > blkcipher_walk_virt_block(&desc, &walk, BLOCK_SIZE); > while (walk.nbytes >= BLOCK_SIZE) { > size_t chunk_len = rounddown(walk.nbytes, BLOCK_SIZE); > poly1305_update(&poly1305_state, walk.src.virt.addr, chunk_len); > blkcipher_walk_done(&desc, &walk, walk.nbytes % BLOCK_SIZE); > } > if (walk.nbytes) { > poly1305_update(&poly1305_state, walk.src.virt.addr, walk.nbytes); > blkcipher_walk_done(&desc, &walk, 0); > } > > Is your suggestion that that in the final if block, walk.src.virt.addr > might be unaligned? Like in the case of the last fragment being 67 > bytes long?
I was not referring to any users in particular, only what users could do. As an example, if you did crypto_shash_update() with 32, 15, then 17 bytes, and the underlying algorithm is poly1305-generic, the last block would end up misaligned. This doesn't appear possible with your pseudocode because it only passes in multiples of the block size until the very end. However I don't see it claimed anywhere that shash API users have to do that. Eric -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html