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dm: only call early_lookup_bdev from early boot context

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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>
Link: https://lore.kernel.org/r/20230531125535.676098-21-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2023-05-31 14:55:31 +02:00 committed by Jens Axboe
parent d4a28d7def
commit 7a126d5bf9
1 changed files with 7 additions and 2 deletions
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9
drivers/md/dm-table.c
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@ -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;
}