From 0868def3e4100591e7a1fdbf3eed1439cc8f7ca3 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Mon, 23 Jul 2018 10:54:57 -0700 Subject: [PATCH] crypto: blkcipher - fix crash flushing dcache in error path Like the skcipher_walk case: scatterwalk_done() is only meant to be called after a nonzero number of bytes have been processed, since scatterwalk_pagedone() will flush the dcache of the *previous* page. But in the error case of blkcipher_walk_done(), e.g. if the input wasn't an integer number of blocks, scatterwalk_done() was actually called after advancing 0 bytes. This caused a crash ("BUG: unable to handle kernel paging request") during '!PageSlab(page)' on architectures like arm and arm64 that define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE, provided that the input was page-aligned as in that case walk->offset == 0. Fix it by reorganizing blkcipher_walk_done() to skip the scatterwalk_advance() and scatterwalk_done() if an error has occurred. This bug was found by syzkaller fuzzing. Reproducer, assuming ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE: #include #include #include int main() { struct sockaddr_alg addr = { .salg_type = "skcipher", .salg_name = "ecb(aes-generic)", }; char buffer[4096] __attribute__((aligned(4096))) = { 0 }; int fd; fd = socket(AF_ALG, SOCK_SEQPACKET, 0); bind(fd, (void *)&addr, sizeof(addr)); setsockopt(fd, SOL_ALG, ALG_SET_KEY, buffer, 16); fd = accept(fd, NULL, NULL); write(fd, buffer, 15); read(fd, buffer, 15); } Reported-by: Liu Chao Fixes: 5cde0af2a982 ("[CRYPTO] cipher: Added block cipher type") Cc: # v2.6.19+ Signed-off-by: Eric Biggers Signed-off-by: Herbert Xu --- crypto/blkcipher.c | 54 ++++++++++++++++++++++++++---------------------------- 1 file changed, 26 insertions(+), 28 deletions(-) diff --git a/crypto/blkcipher.c b/crypto/blkcipher.c index dd4dcab..f93abf1 100644 --- a/crypto/blkcipher.c +++ b/crypto/blkcipher.c @@ -70,19 +70,18 @@ static inline u8 *blkcipher_get_spot(u8 *start, unsigned int len) return max(start, end_page); } -static inline unsigned int blkcipher_done_slow(struct blkcipher_walk *walk, - unsigned int bsize) +static inline void blkcipher_done_slow(struct blkcipher_walk *walk, + unsigned int bsize) { u8 *addr; addr = (u8 *)ALIGN((unsigned long)walk->buffer, walk->alignmask + 1); addr = blkcipher_get_spot(addr, bsize); scatterwalk_copychunks(addr, &walk->out, bsize, 1); - return bsize; } -static inline unsigned int blkcipher_done_fast(struct blkcipher_walk *walk, - unsigned int n) +static inline void blkcipher_done_fast(struct blkcipher_walk *walk, + unsigned int n) { if (walk->flags & BLKCIPHER_WALK_COPY) { blkcipher_map_dst(walk); @@ -96,49 +95,48 @@ static inline unsigned int blkcipher_done_fast(struct blkcipher_walk *walk, scatterwalk_advance(&walk->in, n); scatterwalk_advance(&walk->out, n); - - return n; } int blkcipher_walk_done(struct blkcipher_desc *desc, struct blkcipher_walk *walk, int err) { - unsigned int nbytes = 0; + unsigned int n; /* bytes processed */ + bool more; - if (likely(err >= 0)) { - unsigned int n = walk->nbytes - err; + if (unlikely(err < 0)) + goto finish; - if (likely(!(walk->flags & BLKCIPHER_WALK_SLOW))) - n = blkcipher_done_fast(walk, n); - else if (WARN_ON(err)) { - err = -EINVAL; - goto err; - } else - n = blkcipher_done_slow(walk, n); + n = walk->nbytes - err; + walk->total -= n; + more = (walk->total != 0); - nbytes = walk->total - n; - err = 0; + if (likely(!(walk->flags & BLKCIPHER_WALK_SLOW))) { + blkcipher_done_fast(walk, n); + } else { + if (WARN_ON(err)) { + /* unexpected case; didn't process all bytes */ + err = -EINVAL; + goto finish; + } + blkcipher_done_slow(walk, n); } - scatterwalk_done(&walk->in, 0, nbytes); - scatterwalk_done(&walk->out, 1, nbytes); + scatterwalk_done(&walk->in, 0, more); + scatterwalk_done(&walk->out, 1, more); -err: - walk->total = nbytes; - walk->nbytes = nbytes; - - if (nbytes) { + if (more) { crypto_yield(desc->flags); return blkcipher_walk_next(desc, walk); } - + err = 0; +finish: + walk->nbytes = 0; if (walk->iv != desc->info) memcpy(desc->info, walk->iv, walk->ivsize); if (walk->buffer != walk->page) kfree(walk->buffer); if (walk->page) free_page((unsigned long)walk->page); - return err; } EXPORT_SYMBOL_GPL(blkcipher_walk_done); -- 2.7.4