init: stricter checking of major:minor root= values

In the kernel command-line, previously, root=1:2jakshflaksjdhfa would
be accepted and interpreted just like root=1:2. This patch adds
stricter checking so that additional characters after major:minor are
rejected by root=.

The goal of this change is to help in unifying DM's interpretation of
its block device argument by using existing kernel code (name_to_dev_t).
But DM rejects malformed major:minor pairs, it seems reasonable for
root= to reject them as well.

Signed-off-by: Dan Ehrenberg <dehrenberg@chromium.org>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/init/do_mounts.c b/init/do_mounts.c
index c16adfbe4ad6..8369ffa5f33d 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -226,8 +226,9 @@ dev_t name_to_dev_t(const char *name)
 
         if (strncmp(name, "/dev/", 5) != 0) {
                 unsigned maj, min;
+                char dummy;
 
-                if (sscanf(name, "%u:%u", &maj, &min) == 2) {
+                if (sscanf(name, "%u:%u%c", &maj, &min, &dummy) == 2) {
                         res = MKDEV(maj, min);
                         if (maj != MAJOR(res) || min != MINOR(res))
                                 goto fail;