Commit 4b900641 authored by Eric Biggers's avatar Eric Biggers Committed by Greg Kroah-Hartman
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crypto: blkcipher - fix crash flushing dcache in error path

commit 0868def3


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.


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

	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: default avatarLiu Chao <>
Fixes: 5cde0af2

 ("[CRYPTO] cipher: Added block cipher type")
Cc: <> # v2.6.19+
Signed-off-by: default avatarEric Biggers <>
Signed-off-by: default avatarHerbert Xu <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent 990e4778
......@@ -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) {
......@@ -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);
walk->total = nbytes;
walk->nbytes = nbytes;
if (nbytes) {
if (more) {
return blkcipher_walk_next(desc, walk);
err = 0;
walk->nbytes = 0;
if (walk->iv != desc->info)
memcpy(desc->info, walk->iv, walk->ivsize);
if (walk->buffer != walk->page)
if (walk->page)
free_page((unsigned long)walk->page);
return err;
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