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Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <1843374.1703172614@warthog.procyon.org.uk> <20231223172858.GI201037@kernel.org> To: Linus Torvalds , Edward Adam Davis Cc: dhowells@redhat.com, Simon Horman , Markus Suvanto , Jeffrey E Altman , Marc Dionne , Wang Lei , Jeff Layton , Steve French , Jarkko Sakkinen , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-afs@lists.infradead.org, keyrings@vger.kernel.org, linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org, ceph-devel@vger.kernel.org, netdev@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] keys, dns: Fix missing size check of V1 server-list header Precedence: bulk X-Mailing-List: linux-cifs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-ID: <2592944.1703376169.1@warthog.procyon.org.uk> Date: Sun, 24 Dec 2023 00:02:49 +0000 Message-ID: <2592945.1703376169@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 Hi Linus, Edward, Here's Linus's patch dressed up with a commit message. I would marginally prefer just to insert the missing size check, but I'm also fine with Linus's approach for now until we have different content types or newer versions. Note that I'm not sure whether I should require Linus's S-o-b since he made modifications or whether I should use a Codeveloped-by line for him. David Reviewed-by: Simon Horman --- From: Edward Adam Davis 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: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:377 [inline] print_report+0xc3/0x620 mm/kasan/report.c:488 kasan_report+0xd9/0x110 mm/kasan/report.c:601 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: Simon Horman cc: Linus Torvalds 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 cc: linux-afs@lists.infradead.org cc: linux-cifs@vger.kernel.org cc: linux-nfs@vger.kernel.org cc: ceph-devel@vger.kernel.org cc: keyrings@vger.kernel.org cc: netdev@vger.kernel.org --- net/dns_resolver/dns_key.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) 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)