On Fri, 10 Feb 2017 11:04:34 -0500 Steven Rostedt <[email protected]> wrote:
> On Fri, 10 Feb 2017 22:21:55 +0900 > Masami Hiramatsu <[email protected]> wrote: > > > 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. > > Actually, during the testing I found that we don't need the '\n'. > > echo -n 'p:irq do_IRQ a=@jiffies_64' > kprobe_events > > works just fine. My tests work with 4095 characters. Before and after > my patch. Yeah, I see. I concider the case that if the writer writes 4095 chars command + '\n' + next command, it will fail, that is what I pointed out below note. > > > > 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. Thank you, > > > > Signed-off-by: Masami Hiramatsu <[email protected]> > > --- > > kernel/trace/trace_probe.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c > > index 2a06f1f..847c1e0 100644 > > --- a/kernel/trace/trace_probe.c > > +++ b/kernel/trace/trace_probe.c > > @@ -678,8 +678,9 @@ 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; > > } > -- Masami Hiramatsu <[email protected]>
