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Commit c34837de 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 0868def3e4100591e7a1fdbf3eed1439cc8f7ca3 upstream.

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 <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 <liuchao741@huawei.com>
Fixes: 5cde0af2 ("[CRYPTO] cipher: Added block cipher type")
Cc: <stable@vger.kernel.org> # v2.6.19+
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 58a60fc8

crypto/blkcipher.c

+26 −28
Original line number Diff line number Diff line
@@ -70,7 +70,7 @@ 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,

static inline void blkcipher_done_slow(struct blkcipher_walk *walk,

				       unsigned int bsize)

{

	u8 *addr;
@@ -78,10 +78,9 @@ static inline unsigned int blkcipher_done_slow(struct blkcipher_walk *walk, 
	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,

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);



err:

	walk->total = nbytes;

	walk->nbytes = nbytes;

	scatterwalk_done(&walk->in, 0, more);

	scatterwalk_done(&walk->out, 1, more);



	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);