From 1997b3cb4217b09e49659b634c94da47f0340409 Mon Sep 17 00:00:00 2001 From: Edward Adam Davis Date: Sun, 24 Dec 2023 00:02:49 +0000 Subject: keys, dns: Fix missing size check of V1 server-list header 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 Signed-off-by: Edward Adam Davis Signed-off-by: David Howells Tested-by: David Howells Cc: Edward Adam Davis Cc: Jarkko Sakkinen Cc: Jeffrey E Altman Cc: Wang Lei Cc: Jeff Layton Cc: Steve French Cc: Marc Dionne Cc: "David S. Miller" Cc: Eric Dumazet Cc: Jakub Kicinski Cc: Paolo Abeni Reviewed-by: Simon Horman Signed-off-by: Linus Torvalds --- net/dns_resolver/dns_key.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) (limited to 'net') diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c index 2a6d363763a2..f18ca02aa95a 100644 --- 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_preparsed_payload *prep) 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) -- cgit v1.2.3