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authorOleg Nesterov <oleg@redhat.com>2013-04-29 16:18:10 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-04-29 18:28:19 -0700
commit095d141b2e40665289d44a42d387ffac2841ef82 (patch)
tree3a70ce1eb403955647ab80d1089ea47e95afd9f3 /lib
parent30493cc9dddb68066dcc4878015660fdaa8e0965 (diff)
downloadlinux-095d141b2e40665289d44a42d387ffac2841ef82.tar.gz
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>
Diffstat (limited to 'lib')
-rw-r--r--lib/argv_split.c87
1 files changed, 40 insertions, 47 deletions
diff --git a/lib/argv_split.c b/lib/argv_split.c
index 1e9a6cbc368..e927ed0e18a 100644
--- a/lib/argv_split.c
+++ b/lib/argv_split.c
@@ -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;
-
- argvp = argv;
-
- while (*str) {
- str = skip_spaces(str);
-
- if (*str) {
- const char *p = str;
- char *t;
-
- str = skip_arg(str);
+ char *argv_str;
+ bool was_space;
+ char **argv, **argv_ret;
+ int argc;
+
+ argv_str = kstrndup(str, KMALLOC_MAX_SIZE - 1, gfp);
+ if (!argv_str)
+ return NULL;
+
+ 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;
-
- out:
- return argv;
+ *argv = NULL;
- fail:
- argv_free(argv);
- return NULL;
+ if (argcp)
+ *argcp = argc;
+ return argv_ret;
}
EXPORT_SYMBOL(argv_split);