The patch below does not apply to the 5.15-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-5.15.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-crowbar-posting-c6ba@gregkh' --subject-prefix 'PATCH 5.15.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;