FAILED: patch "[PATCH] crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg" failed to apply to 6.1-stable tree

FAILED: patch "[PATCH] crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg" failed to apply to 6.1-stable tree

[gregkh]

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 1b34cbbf4f011a121ef7b2d7d6e6920a036d5285
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025092107-making-cough-9671@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 1b34cbbf4f011a121ef7b2d7d6e6920a036d5285 Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Tue, 16 Sep 2025 17:20:59 +0800
Subject: [PATCH] crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg

Issuing two writes to the same af_alg socket is bogus as the
data will be interleaved in an unpredictable fashion.  Furthermore,
concurrent writes may create inconsistencies in the internal
socket state.

Disallow this by adding a new ctx->write field that indiciates
exclusive ownership for writing.

Fixes: 8ff590903d5 ("crypto: algif_skcipher - User-space interface for skcipher operations")
Reported-by: Muhammad Alifa Ramdhan <ramdhan@starlabs.sg>
Reported-by: Bing-Jhong Billy Jheng <billy@starlabs.sg>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index 407f2c238f2c..ca6fdcc6c54a 100644
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -970,6 +970,12 @@ int af_alg_sendmsg(struct socket *sock, struct msghdr *msg, size_t size,
 	}
 
 	lock_sock(sk);
+	if (ctx->write) {
+		release_sock(sk);
+		return -EBUSY;
+	}
+	ctx->write = true;
+
 	if (ctx->init && !ctx->more) {
 		if (ctx->used) {
 			err = -EINVAL;
@@ -1105,6 +1111,7 @@ int af_alg_sendmsg(struct socket *sock, struct msghdr *msg, size_t size,
 
 unlock:
 	af_alg_data_wakeup(sk);
+	ctx->write = false;
 	release_sock(sk);
 
 	return copied ?: err;
diff --git a/include/crypto/if_alg.h b/include/crypto/if_alg.h
index f7b3b93f3a49..0c70f3a55575 100644
--- a/include/crypto/if_alg.h
+++ b/include/crypto/if_alg.h
@@ -135,6 +135,7 @@ struct af_alg_async_req {
  *			SG?
  * @enc:		Cryptographic operation to be performed when
  *			recvmsg is invoked.
+ * @write:		True if we are in the middle of a write.
  * @init:		True if metadata has been sent.
  * @len:		Length of memory allocated for this data structure.
  * @inflight:		Non-zero when AIO requests are in flight.
@@ -151,10 +152,11 @@ struct af_alg_ctx {
 	size_t used;
 	atomic_t rcvused;
 
-	bool more;
-	bool merge;
-	bool enc;
-	bool init;
+	u32		more:1,
+			merge:1,
+			enc:1,
+			write:1,
+			init:1;
 
 	unsigned int len;
 

[PATCH 6.1.y 1/2] crypto: af_alg: Convert af_alg_sendpage() to use MSG_SPLICE_PAGES

[Sasha Levin]

From: David Howells <dhowells@redhat.com>

[ Upstream commit fb800fa4c1f5aee1238267252e88a7837e645c02 ]

Convert af_alg_sendpage() to use sendmsg() with MSG_SPLICE_PAGES rather
than directly splicing in the pages itself.

This allows ->sendpage() to be replaced by something that can handle
multiple multipage folios in a single transaction.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Herbert Xu <herbert@gondor.apana.org.au>
cc: "David S. Miller" <davem@davemloft.net>
cc: Eric Dumazet <edumazet@google.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-crypto@vger.kernel.org
cc: netdev@vger.kernel.org
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 crypto/af_alg.c | 52 ++++++++-----------------------------------------
 1 file changed, 8 insertions(+), 44 deletions(-)

diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index fef69d2a6b183..303225c674558 100644
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -988,53 +988,17 @@ EXPORT_SYMBOL_GPL(af_alg_sendmsg);
 ssize_t af_alg_sendpage(struct socket *sock, struct page *page,
 			int offset, size_t size, int flags)
 {
-	struct sock *sk = sock->sk;
-	struct alg_sock *ask = alg_sk(sk);
-	struct af_alg_ctx *ctx = ask->private;
-	struct af_alg_tsgl *sgl;
-	int err = -EINVAL;
+	struct bio_vec bvec;
+	struct msghdr msg = {
+		.msg_flags = flags | MSG_SPLICE_PAGES,
+	};
 
 	if (flags & MSG_SENDPAGE_NOTLAST)
-		flags |= MSG_MORE;
-
-	lock_sock(sk);
-	if (!ctx->more && ctx->used)
-		goto unlock;
-
-	if (!size)
-		goto done;
-
-	if (!af_alg_writable(sk)) {
-		err = af_alg_wait_for_wmem(sk, flags);
-		if (err)
-			goto unlock;
-	}
-
-	err = af_alg_alloc_tsgl(sk);
-	if (err)
-		goto unlock;
-
-	ctx->merge = 0;
-	sgl = list_entry(ctx->tsgl_list.prev, struct af_alg_tsgl, list);
-
-	if (sgl->cur)
-		sg_unmark_end(sgl->sg + sgl->cur - 1);
-
-	sg_mark_end(sgl->sg + sgl->cur);
-
-	get_page(page);
-	sg_set_page(sgl->sg + sgl->cur, page, size, offset);
-	sgl->cur++;
-	ctx->used += size;
-
-done:
-	ctx->more = flags & MSG_MORE;
-
-unlock:
-	af_alg_data_wakeup(sk);
-	release_sock(sk);
+		msg.msg_flags |= MSG_MORE;
 
-	return err ?: size;
+	bvec_set_page(&bvec, page, size, offset);
+	iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, size);
+	return sock_sendmsg(sock, &msg);
 }
 EXPORT_SYMBOL_GPL(af_alg_sendpage);
 
-- 
2.51.0

[PATCH 6.1.y 2/2] crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg

[Sasha Levin]

From: Herbert Xu <herbert@gondor.apana.org.au>

[ Upstream commit 1b34cbbf4f011a121ef7b2d7d6e6920a036d5285 ]

Issuing two writes to the same af_alg socket is bogus as the
data will be interleaved in an unpredictable fashion.  Furthermore,
concurrent writes may create inconsistencies in the internal
socket state.

Disallow this by adding a new ctx->write field that indiciates
exclusive ownership for writing.

Fixes: 8ff590903d5 ("crypto: algif_skcipher - User-space interface for skcipher operations")
Reported-by: Muhammad Alifa Ramdhan <ramdhan@starlabs.sg>
Reported-by: Bing-Jhong Billy Jheng <billy@starlabs.sg>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 crypto/af_alg.c         |  7 +++++++
 include/crypto/if_alg.h | 10 ++++++----
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index 303225c674558..cd3f0a625fb19 100644
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -859,6 +859,12 @@ int af_alg_sendmsg(struct socket *sock, struct msghdr *msg, size_t size,
 	}
 
 	lock_sock(sk);
+	if (ctx->write) {
+		release_sock(sk);
+		return -EBUSY;
+	}
+	ctx->write = true;
+
 	if (ctx->init && !ctx->more) {
 		if (ctx->used) {
 			err = -EINVAL;
@@ -969,6 +975,7 @@ int af_alg_sendmsg(struct socket *sock, struct msghdr *msg, size_t size,
 
 unlock:
 	af_alg_data_wakeup(sk);
+	ctx->write = false;
 	release_sock(sk);
 
 	return copied ?: err;
diff --git a/include/crypto/if_alg.h b/include/crypto/if_alg.h
index a406e281ae571..1424200fe88cf 100644
--- a/include/crypto/if_alg.h
+++ b/include/crypto/if_alg.h
@@ -136,6 +136,7 @@ struct af_alg_async_req {
  *			SG?
  * @enc:		Cryptographic operation to be performed when
  *			recvmsg is invoked.
+ * @write:		True if we are in the middle of a write.
  * @init:		True if metadata has been sent.
  * @len:		Length of memory allocated for this data structure.
  * @inflight:		Non-zero when AIO requests are in flight.
@@ -151,10 +152,11 @@ struct af_alg_ctx {
 	size_t used;
 	atomic_t rcvused;
 
-	bool more;
-	bool merge;
-	bool enc;
-	bool init;
+	u32		more:1,
+			merge:1,
+			enc:1,
+			write:1,
+			init:1;
 
 	unsigned int len;
 
-- 
2.51.0