[PATCH 6.6.y 2/2] cipso: fix optlen corruption in cipso_v4_delopt()

[Sasha Levin <sashal@kernel.org>]

From: Qihang <q.h.hack.winter@gmail.com>

[ Upstream commit 1f1f8e8c5176234fa31858cd25f2e9b88aac0a45 ]

cipso_v4_delopt() recomputes the option length by walking the option
buffer after the CIPSO option has been moved out.  The walk then reads
the stale bytes at the tail of the buffer as option data, and a crafted
setsockopt(IP_OPTIONS) buffer can make it treat one of them as an option
length, increasing opt->opt.optlen beyond the valid option data.

The corrupted length stays on the socket and is later used as the copy
length by getsockopt(IP_OPTIONS) and by the udp/raw/ping sendmsg paths,
where it exceeds the size of the buffers they copy into.

Compute the new length from the intact options before the move and
subtract the CIPSO length, and fill the padding with IPOPT_END.

Assisted-by: LLM
Fixes: 014ab19a69c32 ("selinux: Set socket NetLabel based on connection endpoint")
Cc: stable@vger.kernel.org
Signed-off-by: Qihang <q.h.hack.winter@gmail.com>
Acked-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Dave Miller <davem@davem-thinkpadp1gen8.ibmlond.csb>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/ipv4/cipso_ipv4.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c
index 83f58bb82c867..5ccc6f2524dd8 100644
--- a/net/ipv4/cipso_ipv4.c
+++ b/net/ipv4/cipso_ipv4.c
@@ -2017,6 +2017,10 @@ static int cipso_v4_delopt(struct ip_options_rcu __rcu **opt_ptr)
 		cipso_ptr = &opt->opt.__data[cipso_off];
 		cipso_len = cipso_ptr[1];
 
+		optlen_new = cipso_v4_get_actual_opt_len(opt->opt.__data,
+							 opt->opt.optlen);
+		optlen_new -= cipso_len;
+
 		if (opt->opt.srr > opt->opt.cipso)
 			opt->opt.srr -= cipso_len;
 		if (opt->opt.rr > opt->opt.cipso)
@@ -2030,11 +2034,12 @@ static int cipso_v4_delopt(struct ip_options_rcu __rcu **opt_ptr)
 		memmove(cipso_ptr, cipso_ptr + cipso_len,
 			opt->opt.optlen - cipso_off - cipso_len);
 
-		optlen_new = cipso_v4_get_actual_opt_len(opt->opt.__data,
-							 opt->opt.optlen);
 		hdr_delta = opt->opt.optlen;
 		opt->opt.optlen = (optlen_new + 3) & ~3;
 		hdr_delta -= opt->opt.optlen;
+
+		memset(&opt->opt.__data[optlen_new], IPOPT_END,
+		       opt->opt.optlen - optlen_new);
 	} else {
 		/* only the cipso option was present on the socket so we can
 		 * remove the entire option struct */
-- 
2.53.0