crypto: algif_aead - Fix minimum RX size check for decryption

jira VULN-181881
cve-bf CVE-2026-31431
commit-author Herbert Xu <herbert@gondor.apana.org.au>
commit 3d14bd4

The check for the minimum receive buffer size did not take the
tag size into account during decryption.  Fix this by adding the
required extra length.

	Reported-by: syzbot+aa11561819dc42ebbc7c@syzkaller.appspotmail.com
	Reported-by: Daniel Pouzzner <douzzer@mega.nu>
Fixes: d887c52 ("crypto: algif_aead - overhaul memory management")
	Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
(cherry picked from commit 3d14bd4)
	Signed-off-by: Jonathan Maple <jmaple@ciq.com>

Author: PlaidCat

crypto/algif_aead.c

@@ -168,7 +168,7 @@ static int _aead_recvmsg(struct socket *sock, struct msghdr *msg,
 	if (usedpages < outlen) {
 		size_t less = outlen - usedpages;
 
-		if (used < less) {
+		if (used < less + (ctx->enc ? 0 : as)) {
 			err = -EINVAL;
 			goto free;
 		}