[PATCH 3.16 131/366] tracing/uprobe_event: Fix strncpy corner case

Ben Hutchings
2018-10-14T23:20:22Z

From: Masami Hiramatsu <mhiramat@kernel.org>

commit 50268a3d266ecfdd6c5873d62b2758d9732fc598 upstream.

Fix string fetch function to terminate with NUL.
It is OK to drop the rest of string.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: security@kernel.org
Cc: 范龙飞 <long7573@126.com>
Fixes: 5baaa59ef09e ("tracing/probes: Implement 'memory' fetch method for uprobes")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
kernel/trace/trace_uprobe.c | 2 ++
1 file changed, 2 insertions(+)

--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -149,6 +149,8 @@ static void FETCH_FUNC_NAME(memory, stri
return;

ret = strncpy_from_user(dst, src, maxlen);
+ if (ret == maxlen)
+ dst[--ret] = '\0';

if (ret < 0) { /* Failed to fetch string */
((u8 *)get_rloc_data(dest))[0] = '\0';