[PATCH 20/24] dm: only call early_lookup_bdev from early boot context

Christoph Hellwig
2023-05-31T12:59:13Z

early_lookup_bdev is supposed to only be called from the early boot
code, but dm_get_device calls it as a general fallback when lookup_bdev
fails, which is problematic because early_lookup_bdev bypasses all normal
path based permission checking, and might cause problems with certain
container environments renaming devices.

Switch to only call early_lookup_bdev when dm is built-in and the system
state in not running yet. This means it is still available when tables
are constructed by dm-init.c from the kernel command line, but not
otherwise.

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.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mike Snitzer <snitzer@kernel.org>
---
drivers/md/dm-table.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 1576b408768d4b..2fd5826bfce175 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -326,8 +326,11 @@ static int upgrade_mode(struct dm_dev_internal *dd, fmode_t new_mode,
/*
* Add a device to the list, or just increment the usage count if
* it's already present.
+ *
+ * Note: the __ref annotation is because this function can call the __init
+ * marked early_lookup_bdev when called during early boot code from dm-init.c.
*/
-int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
+int __ref dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
struct dm_dev **result)
{
int r;
@@ -346,8 +349,10 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
return -EOVERFLOW;
} else {
r = lookup_bdev(path, &dev);
- if (r)
+#ifndef MODULE
+ if (r && system_state < SYSTEM_RUNNING)
r = early_lookup_bdev(path, &dev);
+#endif
if (r)
return r;
}
--
2.39.2