crypto: authencesn - Fix src offset when decrypting in-place

jira VULN-181881
cve-bf CVE-2026-31431
commit-author Herbert Xu <herbert@gondor.apana.org.au>
commit 1f48ad3

The src SG list offset wasn't set properly when decrypting in-place,
fix it.

	Reported-by: Wolfgang Walter <linux@stwm.de>
Fixes: e024941 ("crypto: authencesn - Do not place hiseq at end of dst for out-of-place decryption")
	Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
(cherry picked from commit 1f48ad3)
	Signed-off-by: Sultan Alsawaf <sultan@ciq.com>

Author: kerneltoast

crypto/authencesn.c

@@ -257,9 +257,11 @@ static int crypto_authenc_esn_decrypt_tail(struct aead_request *req,
 
 decrypt:
 
-	if (src != dst)
-		src = scatterwalk_ffwd(areq_ctx->src, src, assoclen);
 	dst = scatterwalk_ffwd(areq_ctx->dst, dst, assoclen);
+	if (req->src == req->dst)
+		src = dst;
+	else
+		src = scatterwalk_ffwd(areq_ctx->src, src, assoclen);
 
 	skcipher_request_set_tfm(skreq, ctx->enc);
 	skcipher_request_set_callback(skreq, flags,