--- /dev/null
+From 1997b3cb4217b09e49659b634c94da47f0340409 Mon Sep 17 00:00:00 2001
+From: Edward Adam Davis <eadavis@qq.com>
+Date: Sun, 24 Dec 2023 00:02:49 +0000
+Subject: keys, dns: Fix missing size check of V1 server-list header
+
+From: Edward Adam Davis <eadavis@qq.com>
+
+commit 1997b3cb4217b09e49659b634c94da47f0340409 upstream.
+
+The dns_resolver_preparse() function has a check on the size of the
+payload for the basic header of the binary-style payload, but is missing
+a check for the size of the V1 server-list payload header after
+determining that's what we've been given.
+
+Fix this by getting rid of the the pointer to the basic header and just
+assuming that we have a V1 server-list payload and moving the V1 server
+list pointer inside the if-statement. Dealing with other types and
+versions can be left for when such have been defined.
+
+This can be tested by doing the following with KASAN enabled:
+
+ echo -n -e '\x0\x0\x1\x2' | keyctl padd dns_resolver foo @p
+
+and produces an oops like the following:
+
+ BUG: KASAN: slab-out-of-bounds in dns_resolver_preparse+0xc9f/0xd60 net/dns_resolver/dns_key.c:127
+ Read of size 1 at addr ffff888028894084 by task syz-executor265/5069
+ ...
+ Call Trace:
+ dns_resolver_preparse+0xc9f/0xd60 net/dns_resolver/dns_key.c:127
+ __key_create_or_update+0x453/0xdf0 security/keys/key.c:842
+ key_create_or_update+0x42/0x50 security/keys/key.c:1007
+ __do_sys_add_key+0x29c/0x450 security/keys/keyctl.c:134
+ do_syscall_x64 arch/x86/entry/common.c:52 [inline]
+ do_syscall_64+0x40/0x110 arch/x86/entry/common.c:83
+ entry_SYSCALL_64_after_hwframe+0x62/0x6a
+
+This patch was originally by Edward Adam Davis, but was modified by
+Linus.
+
+Fixes: b946001d3bb1 ("keys, dns: Allow key types (eg. DNS) to be reclaimed immediately on expiry")
+Reported-and-tested-by: syzbot+94bbb75204a05da3d89f@syzkaller.appspotmail.com
+Link: https://lore.kernel.org/r/0000000000009b39bc060c73e209@google.com/
+Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
+Signed-off-by: Edward Adam Davis <eadavis@qq.com>
+Signed-off-by: David Howells <dhowells@redhat.com>
+Tested-by: David Howells <dhowells@redhat.com>
+Cc: Edward Adam Davis <eadavis@qq.com>
+Cc: Jarkko Sakkinen <jarkko@kernel.org>
+Cc: Jeffrey E Altman <jaltman@auristor.com>
+Cc: Wang Lei <wang840925@gmail.com>
+Cc: Jeff Layton <jlayton@redhat.com>
+Cc: Steve French <sfrench@us.ibm.com>
+Cc: Marc Dionne <marc.dionne@auristor.com>
+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>
+Reviewed-by: Simon Horman <horms@kernel.org>
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+Cc: Jeffrey E Altman <jaltman@auristor.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ net/dns_resolver/dns_key.c | 19 +++++++++----------
+ 1 file changed, 9 insertions(+), 10 deletions(-)
+
+--- a/net/dns_resolver/dns_key.c
++++ b/net/dns_resolver/dns_key.c
+@@ -91,8 +91,6 @@ const struct cred *dns_resolver_cache;
+ static int
+ dns_resolver_preparse(struct key_preparsed_payload *prep)
+ {
+- const struct dns_server_list_v1_header *v1;
+- const struct dns_payload_header *bin;
+ struct user_key_payload *upayload;
+ unsigned long derrno;
+ int ret;
+@@ -103,27 +101,28 @@ dns_resolver_preparse(struct key_prepars
+ return -EINVAL;
+
+ if (data[0] == 0) {
++ const struct dns_server_list_v1_header *v1;
++
+ /* It may be a server list. */
+- if (datalen <= sizeof(*bin))
++ if (datalen <= sizeof(*v1))
+ return -EINVAL;
+
+- bin = (const struct dns_payload_header *)data;
+- kenter("[%u,%u],%u", bin->content, bin->version, datalen);
+- if (bin->content != DNS_PAYLOAD_IS_SERVER_LIST) {
++ v1 = (const struct dns_server_list_v1_header *)data;
++ kenter("[%u,%u],%u", v1->hdr.content, v1->hdr.version, datalen);
++ if (v1->hdr.content != DNS_PAYLOAD_IS_SERVER_LIST) {
+ pr_warn_ratelimited(
+ "dns_resolver: Unsupported content type (%u)\n",
+- bin->content);
++ v1->hdr.content);
+ return -EINVAL;
+ }
+
+- if (bin->version != 1) {
++ if (v1->hdr.version != 1) {
+ pr_warn_ratelimited(
+ "dns_resolver: Unsupported server list version (%u)\n",
+- bin->version);
++ v1->hdr.version);
+ return -EINVAL;
+ }
+
+- v1 = (const struct dns_server_list_v1_header *)bin;
+ if ((v1->status != DNS_LOOKUP_GOOD &&
+ v1->status != DNS_LOOKUP_GOOD_WITH_BAD)) {
+ if (prep->expiry == TIME64_MAX)