Commit 095d141b authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

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: default avatarOleg Nesterov <oleg@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 30493cc9

lib/argv_split.c

+40 −47
Original line number Diff line number Diff line
@@ -8,23 +8,17 @@ 
#include <linux/slab.h>

#include <linux/export.h>



static const char *skip_arg(const char *cp)

{

	while (*cp && !isspace(*cp))

		cp++;



	return cp;

}



static int count_argc(const char *str)

{

	int count = 0;

	bool was_space;



	while (*str) {

		str = skip_spaces(str);

		if (*str) {

	for (was_space = true; *str; str++) {

		if (isspace(*str)) {

			was_space = true;

		} else if (was_space) {

			was_space = false;

			count++;

			str = skip_arg(str);

		}

	}
@@ -39,10 +33,8 @@ static int count_argc(const char *str) 
 */

void argv_free(char **argv)

{

	char **p;

	for (p = argv; *p; p++)

		kfree(*p);



	argv--;

	kfree(argv[0]);

	kfree(argv);

}

EXPORT_SYMBOL(argv_free);
@@ -59,43 +51,44 @@ EXPORT_SYMBOL(argv_free); 
 * considered to be a single argument separator.  The returned array

 * is always NULL-terminated.  Returns NULL on memory allocation

 * failure.

 *

 * The source string at `str' may be undergoing concurrent alteration via

 * userspace sysctl activity (at least).  The argv_split() implementation

 * attempts to handle this gracefully by taking a local copy to work on.

 */

char **argv_split(gfp_t gfp, const char *str, int *argcp)

{

	int argc = count_argc(str);

	char **argv = kzalloc(sizeof(*argv) * (argc+1), gfp);

	char **argvp;



	if (argv == NULL)

		goto out;



	if (argcp)

		*argcp = argc;

	char *argv_str;

	bool was_space;

	char **argv, **argv_ret;

	int argc;



	argvp = argv;



	while (*str) {

		str = skip_spaces(str);



		if (*str) {

			const char *p = str;

			char *t;

	argv_str = kstrndup(str, KMALLOC_MAX_SIZE - 1, gfp);

	if (!argv_str)

		return NULL;



			str = skip_arg(str);

	argc = count_argc(argv_str);

	argv = kmalloc(sizeof(*argv) * (argc + 2), gfp);

	if (!argv) {

		kfree(argv_str);

		return NULL;

	}



			t = kstrndup(p, str-p, gfp);

			if (t == NULL)

				goto fail;

			*argvp++ = t;

	*argv = argv_str;

	argv_ret = ++argv;

	for (was_space = true; *argv_str; argv_str++) {

		if (isspace(*argv_str)) {

			was_space = true;

			*argv_str = 0;

		} else if (was_space) {

			was_space = false;

			*argv++ = argv_str;

		}

	}

	*argvp = NULL;

	*argv = NULL;



  out:

	return argv;



  fail:

	argv_free(argv);

	return NULL;

	if (argcp)

		*argcp = argc;

	return argv_ret;

}

EXPORT_SYMBOL(argv_split);

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