[PATCH] dm-verity: fix dm_is_verity_target() when dm-verity is builtin

[PATCH] dm-verity: fix dm_is_verity_target() when dm-verity is builtin

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

When CONFIG_DM_VERITY=y, dm_is_verity_target() returned true for any
builtin dm target, not just dm-verity.  Fix this by checking for
verity_target instead of THIS_MODULE (which is NULL for builtin code).

Fixes: b6c1c5745ccc ("dm: Add verity helpers for LoadPin")
Cc: stable@vger.kernel.org
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 drivers/md/dm-verity-target.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index 0a2399d958b7..cf659c8feb29 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -1519,18 +1519,10 @@ static int verity_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	verity_dtr(ti);
 
 	return r;
 }
 
-/*
- * Check whether a DM target is a verity target.
- */
-bool dm_is_verity_target(struct dm_target *ti)
-{
-	return ti->type->module == THIS_MODULE;
-}
-
 /*
  * Get the verity mode (error behavior) of a verity target.
  *
  * Returns the verity mode of the target, or -EINVAL if 'ti' is not a verity
  * target.
@@ -1580,10 +1572,18 @@ static struct target_type verity_target = {
 	.iterate_devices = verity_iterate_devices,
 	.io_hints	= verity_io_hints,
 };
 module_dm(verity);
 
+/*
+ * Check whether a DM target is a verity target.
+ */
+bool dm_is_verity_target(struct dm_target *ti)
+{
+	return ti->type == &verity_target;
+}
+
 MODULE_AUTHOR("Mikulas Patocka <mpatocka@redhat.com>");
 MODULE_AUTHOR("Mandeep Baines <msb@chromium.org>");
 MODULE_AUTHOR("Will Drewry <wad@chromium.org>");
 MODULE_DESCRIPTION(DM_NAME " target for transparent disk integrity checking");
 MODULE_LICENSE("GPL");

base-commit: ed28fe59c042e9b5bf3b15050aa6ee67834dc852
-- 
2.45.2

Re: [PATCH] dm-verity: fix dm_is_verity_target() when dm-verity is builtin

[Kees Cook]

On Wed, Jul 03, 2024 at 01:08:13PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> When CONFIG_DM_VERITY=y, dm_is_verity_target() returned true for any
> builtin dm target, not just dm-verity.  Fix this by checking for
> verity_target instead of THIS_MODULE (which is NULL for builtin code).
> 
> Fixes: b6c1c5745ccc ("dm: Add verity helpers for LoadPin")
> Cc: stable@vger.kernel.org
> Cc: Matthias Kaehlcke <mka@chromium.org>
> Cc: Kees Cook <keescook@chromium.org>
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Ah! Nice catch.

Reviewed-by: Kees Cook <kees@kernel.org>

-- 
Kees Cook