Patch "crypto: salsa20 - fix blkcipher_walk API usage" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

crypto: salsa20 - fix blkcipher_walk API usage

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
crypto-salsa20-fix-blkcipher_walk-api-usage.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Eric Biggers <[email protected]>
Date: Tue, 28 Nov 2017 20:56:59 -0800
Subject: crypto: salsa20 - fix blkcipher_walk API usage

From: Eric Biggers <[email protected]>

commit ecaaab5649781c5a0effdaf298a925063020500e upstream.

When asked to encrypt or decrypt 0 bytes, both the generic and x86 implementations of Salsa20 crash in blkcipher_walk_done(), either when doing 'kfree(walk->buffer)' or 'free_page((unsigned long)walk->page)', because walk->buffer and walk->page have not been initialized.

The bug is that Salsa20 is calling blkcipher_walk_done() even when nothing is in 'walk.nbytes'. But blkcipher_walk_done() is only meant to be called when a nonzero number of bytes have been provided.

The broken code is part of an optimization that tries to make only one call to salsa20_encrypt_bytes() to process inputs that are not evenly divisible by 64 bytes. To fix the bug, just remove this "optimization" and use the blkcipher_walk API the same way all the other users do.

Reproducer:

    #include <linux/if_alg.h>
    #include <sys/socket.h>
    #include <unistd.h>

    int main()
    {
            int algfd, reqfd;
            struct sockaddr_alg addr = {
                    .salg_type = "skcipher",
                    .salg_name = "salsa20",
            };
            char key[16] = { 0 };

            algfd = socket(AF_ALG, SOCK_SEQPACKET, 0);
            bind(algfd, (void *)&addr, sizeof(addr));
            reqfd = accept(algfd, 0, 0);
            setsockopt(algfd, SOL_ALG, ALG_SET_KEY, key, sizeof(key));
            read(reqfd, key, sizeof(key));
    }

---
 arch/x86/crypto/salsa20_glue.c |    7 -------
 crypto/salsa20_generic.c       |    7 -------
 2 files changed, 14 deletions(-)

@@ -59,13 +59,6 @@ static int encrypt(struct blkcipher_desc
 
 	salsa20_ivsetup(ctx, walk.iv);
 
-	if (likely(walk.nbytes == nbytes))
-	{
-		salsa20_encrypt_bytes(ctx, walk.src.virt.addr,
-				      walk.dst.virt.addr, nbytes);
-		return blkcipher_walk_done(desc, &walk, 0);
-	}
-
 	while (walk.nbytes >= 64) {
 		salsa20_encrypt_bytes(ctx, walk.src.virt.addr,
 				      walk.dst.virt.addr,

@@ -188,13 +188,6 @@ static int encrypt(struct blkcipher_desc
 
 	salsa20_ivsetup(ctx, walk.iv);
 
-	if (likely(walk.nbytes == nbytes))
-	{
-		salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
-				      walk.src.virt.addr, nbytes);
-		return blkcipher_walk_done(desc, &walk, 0);
-	}
-
 	while (walk.nbytes >= 64) {
 		salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
 				      walk.src.virt.addr,

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/crypto-algif_aead-fix-reference-counting-of-null-skcipher.patch queue-4.14/crypto-salsa20-fix-blkcipher_walk-api-usage.patch queue-4.14/crypto-rsa-fix-buffer-overread-when-stripping-leading-zeroes.patch queue-4.14/crypto-hmac-require-that-the-underlying-hash-algorithm-is-unkeyed.patch queue-4.14/crypto-af_alg-fix-null-pointer-dereference-in.patch