linux-kernel - [PATCH 3.4 47/65] tracing/filter: Do not allow infix to exceed end of string

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1445302095-4695-47-git-send-email-lizf@kernel.org>
Date:	Tue, 20 Oct 2015 08:47:57 +0800
From:	lizf@...nel.org
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	"Steven Rostedt (Red Hat)" <rostedt@...dmis.org>,
	Zefan Li <lizefan@...wei.com>
Subject: [PATCH 3.4 47/65] tracing/filter: Do not allow infix to exceed end of string

From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>

3.4.110-rc1 review patch.  If anyone has any objections, please let me know.

------------------

commit 6b88f44e161b9ee2a803e5b2b1fbcf4e20e8b980 upstream.

While debugging a WARN_ON() for filtering, I found that it is possible
for the filter string to be referenced after its end. With the filter:

 # echo '>' > /sys/kernel/debug/events/ext4/ext4_truncate_exit/filter

The filter_parse() function can call infix_get_op() which calls
infix_advance() that updates the infix filter pointers for the cnt
and tail without checking if the filter is already at the end, which
will put the cnt to zero and the tail beyond the end. The loop then calls
infix_next() that has

	ps->infix.cnt--;
	return ps->infix.string[ps->infix.tail++];

The cnt will now be below zero, and the tail that is returned is
already passed the end of the filter string. So far the allocation
of the filter string usually has some buffer that is zeroed out, but
if the filter string is of the exact size of the allocated buffer
there's no guarantee that the charater after the nul terminating
character will be zero.

Luckily, only root can write to the filter.

Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Zefan Li <lizefan@...wei.com>
---
 kernel/trace/trace_events_filter.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index ae6c572..096d774 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -1044,6 +1044,9 @@ static void parse_init(struct filter_parse_state *ps,

 static char infix_next(struct filter_parse_state *ps)
 {
+	if (!ps->infix.cnt)
+		return 0;
+
 	ps->infix.cnt--;

 	return ps->infix.string[ps->infix.tail++];
@@ -1059,6 +1062,9 @@ static char infix_peek(struct filter_parse_state *ps)

 static void infix_advance(struct filter_parse_state *ps)
 {
+	if (!ps->infix.cnt)
+		return;
+
 	ps->infix.cnt--;
 	ps->infix.tail++;
 }
-- 
1.9.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/