[PATCH 21/24] PM: hibernate: don't use early_lookup_bdev in resume_store

Christoph Hellwig
2023-05-31T12:59:22Z

resume_store is a sysfs attribute written during normal kernel runtime,
and it should not use the early_lookup_bdev API that bypasses all normal
path based permission checking, and might cause problems with certain
container environments renaming devices.

Switch to lookup_bdev, which does a normal path lookup instead, and fall
back to trying to parse a numeric dev_t just like early_lookup_bdev did.

Note that this strictly speaking changes the kernel ABI as the PARTUUID=
and PARTLABEL= style syntax is now not available during a running
systems. They never were intended for that, but this breaks things
we'll have to figure out a way to make them available again. But if
avoidable in any way I'd rather avoid that.

Fixes: 421a5fa1a6cf ("PM / hibernate: use name_to_dev_t to parse resume")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
---
kernel/power/hibernate.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index c52dedb9f7c8e8..7ae95ec72f9902 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -1178,7 +1178,23 @@ static ssize_t resume_store(struct kobject *kobj, struct kobj_attribute *attr,
if (!name)
return -ENOMEM;

- error = early_lookup_bdev(name, &dev);
+ error = lookup_bdev(name, &dev);
+ if (error) {
+ unsigned maj, min, offset;
+ char *p, dummy;
+
+ if (sscanf(name, "%u:%u%c", &maj, &min, &dummy) == 2 ||
+ sscanf(name, "%u:%u:%u:%c", &maj, &min, &offset,
+ &dummy) == 3) {
+ dev = MKDEV(maj, min);
+ if (maj != MAJOR(dev) || min != MINOR(dev))
+ error = -EINVAL;
+ } else {
+ dev = new_decode_dev(simple_strtoul(name, &p, 16));
+ if (*p)
+ error = -EINVAL;
+ }
+ }
kfree(name);
if (error)
return error;
--
2.39.2