argv_split(): teach it to handle mutable strings
argv_split() allocates argv[count_argc(str)] array and assumes that it
will find the same number of arguments later. This is obviously wrong if
this string can be changed, say, by sysctl.
With this patch argv_split() kstrndup's the whole string and does not
split it, we simply replace the spaces with zeroes and keep the allocated
memory in argv[-1] for argv_free(arg).
We do not use argv[0] because:
- str can be all-spaces or empty. In fact this case is fine,
we could kfree() it before return, but:
- str can have a space at the start, and we can not rely on
kstrndup(skip_spaces(str)) because it can equally race if
this string is mutable.
Also, simplify count_argc() and kill the no longer used skip_arg().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>