5.10-stable review patch. If anyone has any objections, please let me know.
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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)