[PATCH 6.6 178/299] dm-integrity, dm-verity: reduce stack usage for recheck

Greg Kroah-Hartman
2024-02-27T13:54:59Z

From: Arnd Bergmann <arnd@arndb.de>

commit 66ad2fbcdbeab0edfd40c5d94f32f053b98c2320 upstream.

The newly added integrity_recheck() function has another larger stack
allocation, just like its caller integrity_metadata(). When it gets
inlined, the combination of the two exceeds the warning limit for 32-bit
architectures and possibly risks an overflow when this is called from
a deep call chain through a file system:

drivers/md/dm-integrity.c:1767:13: error: stack frame size (1048) exceeds limit (1024) in 'integrity_metadata' [-Werror,-Wframe-larger-than]
1767 | static void integrity_metadata(struct work_struct *w)

Since the caller at this point is done using its checksum buffer,
just reuse the same buffer in the new function to avoid the double
allocation.

[Mikulas: add "noinline" to integrity_recheck and verity_recheck.
These functions are only called on error, so they shouldn't bloat the
stack frame or code size of the caller.]

Fixes: c88f5e553fe3 ("dm-integrity: recheck the integrity tag after a failure")
Fixes: 9177f3c0dea6 ("dm-verity: recheck the hash after a failure")
Cc: stable@vger.kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/md/dm-integrity.c | 10 ++++------
drivers/md/dm-verity-target.c | 4 ++--
2 files changed, 6 insertions(+), 8 deletions(-)

--- a/drivers/md/dm-integrity.c
+++ b/drivers/md/dm-integrity.c
@@ -1701,14 +1701,13 @@ failed:
get_random_bytes(result, ic->tag_size);
}

-static void integrity_recheck(struct dm_integrity_io *dio)
+static noinline void integrity_recheck(struct dm_integrity_io *dio, char *checksum)
{
struct bio *bio = dm_bio_from_per_bio_data(dio, sizeof(struct dm_integrity_io));
struct dm_integrity_c *ic = dio->ic;
struct bvec_iter iter;
struct bio_vec bv;
sector_t sector, logical_sector, area, offset;
- char checksum_onstack[max_t(size_t, HASH_MAX_DIGESTSIZE, MAX_TAG_SIZE)];
struct page *page;
void *buffer;

@@ -1744,9 +1743,8 @@ static void integrity_recheck(struct dm_
goto free_ret;
}

- integrity_sector_checksum(ic, logical_sector, buffer,
- checksum_onstack);
- r = dm_integrity_rw_tag(ic, checksum_onstack, &dio->metadata_block,
+ integrity_sector_checksum(ic, logical_sector, buffer, checksum);
+ r = dm_integrity_rw_tag(ic, checksum, &dio->metadata_block,
&dio->metadata_offset, ic->tag_size, TAG_CMP);
if (r) {
if (r > 0) {
@@ -1861,7 +1859,7 @@ again:
checksums_ptr - checksums, dio->op == REQ_OP_READ ? TAG_CMP : TAG_WRITE);
if (unlikely(r)) {
if (r > 0) {
- integrity_recheck(dio);
+ integrity_recheck(dio, checksums);
goto skip_io;
}
if (likely(checksums != checksums_onstack))
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -491,8 +491,8 @@ static int verity_recheck_copy(struct dm
return 0;
}

-static int verity_recheck(struct dm_verity *v, struct dm_verity_io *io,
- struct bvec_iter start, sector_t cur_block)
+static noinline int verity_recheck(struct dm_verity *v, struct dm_verity_io *io,
+ struct bvec_iter start, sector_t cur_block)
{
struct page *page;
void *buffer;