On 2/2/2024 10:51 AM, Mike Snitzer wrote:
On Tue, Jan 30 2024 at 5:37P -0500,
Fan Wu <wufan@xxxxxxxxxxxxxxxxxxx> wrote:
The device-mapper has a flag to mark targets as singleton, which is a
required flag for immutable targets. Without this flag, multiple
dm-verity targets can be added to a mapped device, which has no
practical use cases and will let dm_table_get_immutable_target return
NULL. This patch adds the missing flag, restricting only one
dm-verity target per mapped device.
Signed-off-by: Fan Wu <wufan@xxxxxxxxxxxxxxxxxxx>
---
v1-v10:
+ Not present
v11:
+ Introduced
v12:
+ No changes
---
drivers/md/dm-verity-target.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index 14e58ae70521..66a850c02be4 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -1507,7 +1507,7 @@ int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest, unsigned i
static struct target_type verity_target = {
.name = "verity",
- .features = DM_TARGET_IMMUTABLE,
+ .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
.version = {1, 9, 0},
.module = THIS_MODULE,
.ctr = verity_ctr,
--
2.43.0
It is true this change will cause dm_table_get_immutable_target() to
not return NULL, but: I'm curious how that is meaningful in the
context of dm-verity? (given the only caller of
dm_table_get_immutable_target() is request-based DM code in DM core.)
Thanks,
Mike
Sorry for the confusion. The reference of
dm_table_get_immutable_target() is only to justify an immutable target
should also be a
singleton(https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/md/dm-table.c#n982).
It is not directly related to dm-verity.
In the context of dm-verity. I found although veritysetup does ensure
the dm-verity target as a singleton, users can still use dmsetup to
configure multiple dm-verity targets within a single map table. This
leads to a situation where only the first target can be accessed.
Therefore to prevent this and similar misuse, I propose introducing
DM_TARGET_SINGLETON to allow the kernel to enforce dm-verity targets as
singletons.
Thanks,
Fan
