[PATCH 6.1 115/195] dm-integrity, dm-verity: reduce stack usage for recheck

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6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Arnd Bergmann <arnd@xxxxxxxx>

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@xxxxxxxxxxxxxxx
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 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) {
@@ -1859,7 +1857,7 @@ 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
@@ -483,8 +483,8 @@ 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;






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