If an AF_ALG socket bound to a hashing algorithm is sent a zero-length
message with MSG_MORE set and then recvmsg() is called without first
sending another message without MSG_MORE set to end the operation, an oops
will occur because the crypto context and result doesn't now get set up in
advance because hash_sendmsg() now defers that as long as possible in the
hope that it can use crypto_ahash_digest() - and then because the message
is zero-length, it the data wrangling loop is skipped.
Fix this by always making a pass of the loop, even in the case that no data
is provided to the sendmsg().
Fix also extract_iter_to_sg() to handle a zero-length iterator by returning
0 immediately.
Whilst we're at it, remove the code to create a kvmalloc'd scatterlist if
we get more than ALG_MAX_PAGES - this shouldn't happen.
Fixes: c662b043cdca ("crypto: af_alg/hash: Support MSG_SPLICE_PAGES")
Reported-by: syzbot+13a08c0bf4d212766c3c@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/000000000000b928f705fdeb873a@xxxxxxxxxx/
Reported-by: syzbot+14234ccf6d0ef629ec1a@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/000000000000c047db05fdeb8790@xxxxxxxxxx/
Reported-by: syzbot+4e2e47f32607d0f72d43@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/000000000000bcca3205fdeb87fb@xxxxxxxxxx/
Reported-by: syzbot+472626bb5e7c59fb768f@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/000000000000b55d8805fdeb8385@xxxxxxxxxx/
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Tested-by: syzbot+13a08c0bf4d212766c3c@xxxxxxxxxxxxxxxxxxxxxxxxx
Tested-by: syzbot+14234ccf6d0ef629ec1a@xxxxxxxxxxxxxxxxxxxxxxxxx
Tested-by: syzbot+4e2e47f32607d0f72d43@xxxxxxxxxxxxxxxxxxxxxxxxx
Tested-by: syzbot+472626bb5e7c59fb768f@xxxxxxxxxxxxxxxxxxxxxxxxx
cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
cc: Eric Dumazet <edumazet@xxxxxxxxxx>
cc: Jakub Kicinski <kuba@xxxxxxxxxx>
cc: Paolo Abeni <pabeni@xxxxxxxxxx>
cc: Jens Axboe <axboe@xxxxxxxxx>
cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
cc: linux-crypto@xxxxxxxxxxxxxxx
cc: netdev@xxxxxxxxxxxxxxx
---
crypto/algif_hash.c | 21 +++++----------------
lib/scatterlist.c | 2 +-
2 files changed, 6 insertions(+), 17 deletions(-)
diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c
index dfb048cefb60..1176533a55c9 100644
--- a/crypto/algif_hash.c
+++ b/crypto/algif_hash.c
@@ -83,26 +83,14 @@ static int hash_sendmsg(struct socket *sock, struct msghdr *msg,
ctx->more = false;
- while (msg_data_left(msg)) {
+ do {
ctx->sgl.sgt.sgl = ctx->sgl.sgl;
ctx->sgl.sgt.nents = 0;
ctx->sgl.sgt.orig_nents = 0;
err = -EIO;
npages = iov_iter_npages(&msg->msg_iter, max_pages);
- if (npages == 0)
- goto unlock_free;
-
- if (npages > ARRAY_SIZE(ctx->sgl.sgl)) {
- err = -ENOMEM;
- ctx->sgl.sgt.sgl =
- kvmalloc(array_size(npages,
- sizeof(*ctx->sgl.sgt.sgl)),
- GFP_KERNEL);
- if (!ctx->sgl.sgt.sgl)
- goto unlock_free;
- }
- sg_init_table(ctx->sgl.sgl, npages);
+ sg_init_table(ctx->sgl.sgl, max_t(size_t, npages, 1));
ctx->sgl.need_unpin = iov_iter_extract_will_pin(&msg->msg_iter);
@@ -111,7 +99,8 @@ static int hash_sendmsg(struct socket *sock, struct msghdr *msg,
if (err < 0)
goto unlock_free;
len = err;
- sg_mark_end(ctx->sgl.sgt.sgl + ctx->sgl.sgt.nents - 1);
+ if (len > 0)
+ sg_mark_end(ctx->sgl.sgt.sgl + ctx->sgl.sgt.nents - 1);
if (!msg_data_left(msg)) {
err = hash_alloc_result(sk, ctx);
@@ -148,7 +137,7 @@ static int hash_sendmsg(struct socket *sock, struct msghdr *msg,
copied += len;
af_alg_free_sg(&ctx->sgl);
- }
+ } while (msg_data_left(msg));
ctx->more = msg->msg_flags & MSG_MORE;
err = 0;
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index e97d7060329e..77a7b18ee751 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -1340,7 +1340,7 @@ ssize_t extract_iter_to_sg(struct iov_iter *iter, size_t maxsize,
struct sg_table *sgtable, unsigned int sg_max,
iov_iter_extraction_t extraction_flags)
{
- if (maxsize == 0)
+ if (!maxsize || !iter->count)
return 0;
switch (iov_iter_type(iter)) {
