From: Masami Hiramatsu <mhiramat@kernel.org>
Date: Tue, 10 Apr 2018 12:20:08 +0000 (+0900)
Subject: tracing/uprobe_event: Fix strncpy corner case
X-Git-Tag: v4.1.52~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=204663f60b89317b732cb4368084a0d6975d6060;p=thirdparty%2Fkernel%2Fstable.git

tracing/uprobe_event: Fix strncpy corner case

[ Upstream commit 50268a3d266ecfdd6c5873d62b2758d9732fc598 ]

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: Sasha Levin <alexander.levin@microsoft.com>
---

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 6dd022c7b5bcb..1b11c3c21a292 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -149,6 +149,8 @@ static void FETCH_FUNC_NAME(memory, string)(struct pt_regs *regs,
 		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';