[PATCH v2 2/3] init: Stricter checking of major:minor root= values

From: Dan Ehrenberg
Date: Tue Feb 10 2015 - 18:21:08 EST

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 patch is to help in unifying dm's interpretation of
its block device argument with the interpretation in other parts of
the kernel. dm rejects malformed major:minor pairs, and it seems
reasonable that root= could reject them as well.

Signed-off-by: Dan Ehrenberg <dehrenberg@xxxxxxxxxxxx>
init/do_mounts.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/init/do_mounts.c b/init/do_mounts.c
index 4b2daf1..24f359f 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;

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