Re: [PATCH v3 1/2] init/do_mounts.c: ignore final \n in name_to_dev_t

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 29 Jan 2014 10:29:56 -0800 Sebastian Capella <sebastian.capella@linaro.org> wrote:

> Hi Andrew,
> 
> By the way, I do see a call (sysfs_streq) in use for this purpose
> other places.  Sorry, I didn't find it while looking at the original
> problem.  I'm not sure if this is preferable, but it appears to have
> been added specifically for the strings coming through sysfs.

Yes, I wrote it ;)

I didn't think sysfs_streq() is well suited to this problem.  And the
issue of possibly-null-terminated-strings coming in from userspace is a
common one, so it is desirable that we build up the suite of utilities
to handle this.

There are probably quite a lot of open-coded \n trimming loops which
can be cleaned up using such tools.

	grep -r "if .* == '\\\n'" .

> My preference is copying the string and cleaning it up before passing
> it to internal functions, even though we incur an allocation.

Yes.  Here on the kernel/userspace boundary we are typically running in
GFP_KERNEL context and the code is not performance critical - it is a
good fit.