Re: [PATCH 1/2] Smack: fix another vsscanf out of bounds
From: Casey Schaufler <casey@schaufler-ca.com>
Date: 2020-07-23 16:38:32
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On 7/23/2020 8:22 AM, Dan Carpenter wrote:
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 <redacted>Thanks. I'll be testing these and take them assuming they pass.
quoted hunk ↗ jump to hunk
--- 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;