From: Dan Carpenter <dan.carpenter@oracle.com>
To: Casey Schaufler <casey@schaufler-ca.com>
Cc: James Morris <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com
Subject: [PATCH 1/2] Smack: fix another vsscanf out of bounds
Date: Thu, 23 Jul 2020 18:22:19 +0300 [thread overview]
Message-ID: <20200723152219.GA302005@mwanda> (raw)
In-Reply-To: <000000000000d282bd05ab0bf532@google.com>
This is similar to commit 84e99e58e8d1 ("Smack: slab-out-of-bounds in
vsscanf") where we added a bounds check on "rule".
Reported-by: syzbot+a22c6092d003d6fe1122@syzkaller.appspotmail.com
Fixes: f7112e6c9abf ("Smack: allow for significantly longer Smack labels v4")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
This check is very straight forward and should fix the bug. But if you
look at the fixes tag we used to rely on the check:
if (count != (SMK_CIPSOMIN + catlen * SMK_DIGITLEN))
and now that has been changed to:
if (format == SMK_FIXED24_FMT &&
count != (SMK_CIPSOMIN + catlen * SMK_DIGITLEN))
goto out;
so it doesn't apply for every format.
security/smack/smackfs.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index c21b656b3263..81c6ceeaa4f9 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -905,6 +905,10 @@ static ssize_t smk_set_cipso(struct file *file, const char __user *buf,
for (i = 0; i < catlen; i++) {
rule += SMK_DIGITLEN;
+ if (rule > data + count) {
+ rc = -EOVERFLOW;
+ goto out;
+ }
ret = sscanf(rule, "%u", &cat);
if (ret != 1 || cat > SMACK_CIPSO_MAXCATNUM)
goto out;
--
2.27.0
next prev parent reply other threads:[~2020-07-23 15:22 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-22 18:32 KASAN: slab-out-of-bounds Read in vsscanf (2) syzbot
2020-07-23 15:22 ` Dan Carpenter [this message]
2020-07-23 16:38 ` [PATCH 1/2] Smack: fix another vsscanf out of bounds Casey Schaufler
2020-07-23 15:23 ` [PATCH 2/2] Smack: prevent underflow in smk_set_cipso() Dan Carpenter
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