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Commit 2ca9bb45 authored by Kees Cook's avatar Kees Cook Committed by Linus Torvalds
Browse files

sysctl: refactor sysctl string writing logic 



Consolidate buffer length checking with new-line/end-of-line checking.
Additionally, instead of reading user memory twice, just do the
assignment during the loop.

This change doesn't affect the potential races here.  It was already
possible to read a sysctl that was in the middle of a write.  In both
cases, the string will always be NULL terminated.  The pre-existing race
remains a problem to be solved.

Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f8808300

kernel/sysctl.c

+4 −7
Original line number Diff line number Diff line
@@ -1717,21 +1717,18 @@ static int _proc_do_string(char *data, int maxlen, int write, 
	}



	if (write) {

		/* Start writing from beginning of buffer. */

		len = 0;

		*ppos += *lenp;

		p = buffer;

		while (len < *lenp) {

		while ((p - buffer) < *lenp && len < maxlen - 1) {

			if (get_user(c, p++))

				return -EFAULT;

			if (c == 0 || c == '\n')

				break;

			len++;

			data[len++] = c;

		}

		if (len >= maxlen)

			len = maxlen-1;

		if(copy_from_user(data, buffer, len))

			return -EFAULT;

		data[len] = 0;

		*ppos += *lenp;

	} else {

		len = strlen(data);

		if (len > maxlen)