From: Masami Hiramatsu <mhiramat@kernel.org>
Date: Fri, 10 Feb 2017 13:21:55 +0000 (+0900)
Subject: tracing/probes: Fix a warning message to show correct maximum length
X-Git-Tag: v4.11-rc1~65^2~1
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=bef5da60595f5706232e2502876f8545743b9b41;p=linux.git

tracing/probes: Fix a warning message to show correct maximum length

Since tracing/*probe_events will accept a probe definition
up to 4096 - 2 ('\n' and '\0') bytes, it must show 4094 instead
of 4096 in warning message.

Note that there is one possible case of exceed 4094. If user
prepare 4096 bytes null-terminated string and syscall write
it with the count == 4095, then it can be accepted. However,
if user puts a '\n' after that, it must rejected.
So IMHO, the warning message should indicate shorter one,
since it is safer.

Link: http://lkml.kernel.org/r/148673290462.2579.7966778294009665632.stgit@devbox

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 11b63328d6fb..52478f033f88 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -679,8 +679,9 @@ ssize_t traceprobe_probes_write(struct file *file, const char __user *buffer,
 				if (done + size < count) {
 					if (buf != kbuf)
 						break;
+					/* This can accept WRITE_BUFSIZE - 2 ('\n' + '\0') */
 					pr_warn("Line length is too long: Should be less than %d\n",
-						WRITE_BUFSIZE);
+						WRITE_BUFSIZE - 2);
 					ret = -EINVAL;
 					goto out;
 				}