On 12/08/2014 11:50 AM, Grant Likely wrote: > On Sat, 6 Dec 2014 14:55:33 +0100 > , Pavel Machek <pavel@xxxxxxx> > wrote: >> Hi! >> >>>> I am accustomed to doing 'echo -n' for most of sysfs anyway. Once in a >>>> while I am a bonehead and forget the '-n' and spend a few minutes >>>> wondering why this thing that worked last week suddenly rejects all >>>> commands. I'm just trying to make my user interface a bit user-friendly. >>>> >>>> I will take out the '\n' stripping and update the documentation. I didn't >>>> realize this would be controversial. >>> >>> Don't. You're doing the right thing by scrubbing your input. Requiring >>> 'echo -n' is just stupid when it is so easy to make work easily. >> >> 'foo\nbar\n' is unusual but valid filename in linux. It is bad idea to >> echo filenames into files in the first place... and arbitrarily >> disallowing certain filenames is not helping. > > Meh. Just because it is a valid linux filename doesn't mean this > interface is forced to accept it. There should be tighter rules about > how the filename can be constructed. Allowing any arbitrary path for any > arbitrary valid linux filename makes for a large attack surface. "echo /bin/mdev > /proc/sys/kernel/hotplug" has worked fine, without the -n, for most of a decade now. Requiring -n on echo would be weird. I note that the filenames in /proc/mounts have an escape syntax for arbitrary embedded weirdness. (To see it in action, mount a path with a space in it.) If you really want to support that, there's presumably code that can be genericized and reappropriated so you can escape a newline you want to keep. But if your input has a normal unescaped trailing newline, it _should_ be ignored. Rob -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
