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authorEric Biggers <ebiggers@google.com>2018-07-23 10:54:56 -0700
committerHerbert Xu <herbert@gondor.apana.org.au>2018-08-03 18:06:04 +0800
commit8088d3dd4d7c6933a65aa169393b5d88d8065672 (patch)
tree454df41eb17db574cc8fa89883678599e69ebcdf
parent2a57c0be225f8c7140f8791819f5afbb6fb34c5a (diff)
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crypto: skcipher - fix crash flushing dcache in error path
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 skcipher_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 skcipher_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 <linux/if_alg.h> #include <sys/socket.h> #include <unistd.h> int main() { struct sockaddr_alg addr = { .salg_type = "skcipher", .salg_name = "cbc(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 <liuchao741@huawei.com> Fixes: b286d8b1a690 ("crypto: skcipher - Add skcipher walk interface") Cc: <stable@vger.kernel.org> # v4.10+ Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
-rw-r--r--crypto/skcipher.c53
1 files changed, 27 insertions, 26 deletions
diff --git a/crypto/skcipher.c b/crypto/skcipher.c
index 835e5d36ad59..0bd8c6caa498 100644
--- a/crypto/skcipher.c
+++ b/crypto/skcipher.c
@@ -95,7 +95,7 @@ static inline u8 *skcipher_get_spot(u8 *start, unsigned int len)
return max(start, end_page);
}
-static int skcipher_done_slow(struct skcipher_walk *walk, unsigned int bsize)
+static void skcipher_done_slow(struct skcipher_walk *walk, unsigned int bsize)
{
u8 *addr;
@@ -103,23 +103,24 @@ static int skcipher_done_slow(struct skcipher_walk *walk, unsigned int bsize)
addr = skcipher_get_spot(addr, bsize);
scatterwalk_copychunks(addr, &walk->out, bsize,
(walk->flags & SKCIPHER_WALK_PHYS) ? 2 : 1);
- return 0;
}
int skcipher_walk_done(struct skcipher_walk *walk, int err)
{
- unsigned int n = walk->nbytes - err;
- unsigned int nbytes;
-
- nbytes = walk->total - n;
-
- if (unlikely(err < 0)) {
- nbytes = 0;
- n = 0;
- } else if (likely(!(walk->flags & (SKCIPHER_WALK_PHYS |
- SKCIPHER_WALK_SLOW |
- SKCIPHER_WALK_COPY |
- SKCIPHER_WALK_DIFF)))) {
+ unsigned int n; /* bytes processed */
+ bool more;
+
+ if (unlikely(err < 0))
+ goto finish;
+
+ n = walk->nbytes - err;
+ walk->total -= n;
+ more = (walk->total != 0);
+
+ if (likely(!(walk->flags & (SKCIPHER_WALK_PHYS |
+ SKCIPHER_WALK_SLOW |
+ SKCIPHER_WALK_COPY |
+ SKCIPHER_WALK_DIFF)))) {
unmap_src:
skcipher_unmap_src(walk);
} else if (walk->flags & SKCIPHER_WALK_DIFF) {
@@ -131,28 +132,28 @@ unmap_src:
skcipher_unmap_dst(walk);
} else if (unlikely(walk->flags & SKCIPHER_WALK_SLOW)) {
if (WARN_ON(err)) {
+ /* unexpected case; didn't process all bytes */
err = -EINVAL;
- nbytes = 0;
- } else
- n = skcipher_done_slow(walk, n);
+ goto finish;
+ }
+ skcipher_done_slow(walk, n);
+ goto already_advanced;
}
- if (err > 0)
- err = 0;
-
- walk->total = nbytes;
- walk->nbytes = nbytes;
-
scatterwalk_advance(&walk->in, n);
scatterwalk_advance(&walk->out, n);
- scatterwalk_done(&walk->in, 0, nbytes);
- scatterwalk_done(&walk->out, 1, nbytes);
+already_advanced:
+ scatterwalk_done(&walk->in, 0, more);
+ scatterwalk_done(&walk->out, 1, more);
- if (nbytes) {
+ if (more) {
crypto_yield(walk->flags & SKCIPHER_WALK_SLEEP ?
CRYPTO_TFM_REQ_MAY_SLEEP : 0);
return skcipher_walk_next(walk);
}
+ err = 0;
+finish:
+ walk->nbytes = 0;
/* Short-circuit for the common/fast path. */
if (!((unsigned long)walk->buffer | (unsigned long)walk->page))