crypto: algif_aead - snapshot IV for async AEAD requests

jira VULN-181877
cve-bf CVE-2026-31431
commit-author Douya Le <ldy3087146292@gmail.com>
commit 5aa58c3

AF_ALG AEAD AIO requests currently use the socket-wide IV buffer during
request processing.  For async requests, later socket activity can
update that shared state before the original request has fully
completed, which can lead to inconsistent IV handling.

Snapshot the IV into per-request storage when preparing the AEAD
request, so in-flight operations no longer depend on mutable socket
state.

Fixes: d887c52 ("crypto: algif_aead - overhaul memory management")
    Cc: stable@kernel.org
    Reported-by: Yuan Tan <yuantan098@gmail.com>
    Reported-by: Yifan Wu <yifanwucs@gmail.com>
    Reported-by: Juefei Pu <tomapufckgml@gmail.com>
    Reported-by: Xin Liu <bird@lzu.edu.cn>
    Co-developed-by: Luxing Yin <tr0jan@lzu.edu.cn>
    Signed-off-by: Luxing Yin <tr0jan@lzu.edu.cn>
    Tested-by: Yucheng Lu <kanolyc@gmail.com>
    Signed-off-by: Douya Le <ldy3087146292@gmail.com>
    Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Author: Herbert Xu

crypto/algif_aead.c

@@ -100,8 +100,10 @@ static int _aead_recvmsg(struct socket *sock, struct msghdr *msg,
 	struct crypto_aead *tfm = aeadc->aead;
 	struct crypto_skcipher *null_tfm = aeadc->null_tfm;
 	unsigned int as = crypto_aead_authsize(tfm);
+	unsigned int ivsize = crypto_aead_ivsize(tfm);
 	struct af_alg_async_req *areq;
 	struct scatterlist *rsgl_src, *tsgl_src = NULL;
+	void *iv;
 	int err = 0;
 	size_t used = 0;		/* [in]  TX bufs to be en/decrypted */
 	size_t outlen = 0;		/* [out] RX bufs produced by kernel */
@@ -153,10 +155,14 @@ static int _aead_recvmsg(struct socket *sock, struct msghdr *msg,
 
 	/* Allocate cipher request for current operation. */
 	areq = af_alg_alloc_areq(sk, sizeof(struct af_alg_async_req) +
-				     crypto_aead_reqsize(tfm));
+				     crypto_aead_reqsize(tfm) + ivsize);
 	if (IS_ERR(areq))
 		return PTR_ERR(areq);
 
+	iv = (u8 *)aead_request_ctx(&areq->cra_u.aead_req) +
+	     crypto_aead_reqsize(tfm);
+	memcpy(iv, ctx->iv, ivsize);
+
 	/* convert iovecs of output buffers into RX SGL */
 	err = af_alg_get_rsgl(sk, msg, flags, areq, outlen, &usedpages);
 	if (err)
@@ -218,7 +224,7 @@ static int _aead_recvmsg(struct socket *sock, struct msghdr *msg,
 
 	/* Initialize the crypto operation */
 	aead_request_set_crypt(&areq->cra_u.aead_req, tsgl_src,
-			       areq->first_rsgl.sgl.sg, used, ctx->iv);
+			       areq->first_rsgl.sgl.sg, used, iv);
 	aead_request_set_ad(&areq->cra_u.aead_req, ctx->aead_assoclen);
 	aead_request_set_tfm(&areq->cra_u.aead_req, tfm);