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

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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>
This commit is contained in:
Masami Hiramatsu 2017-02-10 22:21:55 +09:00 committed by Steven Rostedt (VMware)
parent 8f0994bb8c
commit bef5da6059
1 changed files with 2 additions and 1 deletions
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3
kernel/trace/trace_probe.c
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@ -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;
}