On Tue, Nov 28, 2017 at 08:56:59PM -0800, Eric Biggers wrote:
From: Eric Biggers ebiggers@google.com
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)); }Reported-by: syzbot syzkaller@googlegroups.com Fixes: eb6f13eb9f81 ("[CRYPTO] salsa20_generic: Fix multi-page processing") Cc: stable@vger.kernel.org # v2.6.25+ Signed-off-by: Eric Biggers ebiggers@google.com
Patch applied. Thanks.