From 763dafc520add02a1f4639b500c509acc0ea8e5b Mon Sep 17 00:00:00 2001
From: Paul Moore <paul@paul-moore.com>
Date: Mon, 20 Apr 2020 16:24:34 -0400
Subject: [PATCH] audit: check the length of userspace generated audit records
Git-commit: 763dafc520add02a1f4639b500c509acc0ea8e5b
Patch-mainline: v5.7-rc3
References: git-fixes
Commit 756125289285 ("audit: always check the netlink payload length
in audit_receive_msg()") fixed a number of missing message length
checks, but forgot to check the length of userspace generated audit
records. The good news is that you need CAP_AUDIT_WRITE to submit
userspace audit records, which is generally only given to trusted
processes, so the impact should be limited.
Cc: stable@vger.kernel.org
Fixes: 756125289285 ("audit: always check the netlink payload length in audit_receive_msg()")
Reported-by: syzbot+49e69b4d71a420ceda3e@syzkaller.appspotmail.com
Signed-off-by: Paul Moore <paul@paul-moore.com>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
kernel/audit.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/kernel/audit.c b/kernel/audit.c
index b69c8b460341..87f31bf1f0a0 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1326,6 +1326,9 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
case AUDIT_FIRST_USER_MSG2 ... AUDIT_LAST_USER_MSG2:
if (!audit_enabled && msg_type != AUDIT_USER_AVC)
return 0;
+ /* exit early if there isn't at least one character to print */
+ if (data_len < 2)
+ return -EINVAL;
err = audit_filter(msg_type, AUDIT_FILTER_USER);
if (err == 1) { /* match or error */
--
2.16.4