dm-integrity, dm-verity: reduce stack usage for recheck

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>

diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c
index 44a1dcc06dd7334f13ff98a107dc2ebf8e2d2469..1fc901df84eb163c833e364d21e0a48e65c06239 100644 (file)
--- a/drivers/md/dm-integrity.c
+++ b/drivers/md/dm-integrity.c
@@ -1691,14 +1691,13 @@ 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;
 
@@ -1734,9 +1733,8 @@ static void integrity_recheck(struct dm_integrity_io *dio)
                                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) {
@@ -1851,7 +1849,7 @@ 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))

diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index 06c8b637849c96c1cb2c1c97fa3e58fc713d7023..1b591bfa90d5d6463016e22183dbb5f071e94a75 100644 (file)
--- 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_verity *v, struct dm_verity_io *io,
        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;