FAILED: patch "[PATCH] dm-integrity: don't modify bio's immutable bio_vec in" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x b86f4b790c998afdbc88fe1aa55cfe89c4068726
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023123001-profusely-reassign-059b@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

b86f4b790c99 ("dm-integrity: don't modify bio's immutable bio_vec in integrity_metadata()") 86a3238c7b9b ("dm: change "unsigned" to "unsigned int"")
7533afa1d27b ("dm: send just one event on resize, not two")
5cd6d1d53a1f ("dm integrity: Remove bi_sector that's only used by commented debug code") 22c40e134c4c ("dm cache: Add some documentation to dm-cache-background-tracker.h")
86e4d3e8d183 ("dm-crypt: provide dma_alignment limit in io_hints")
c3adefb5baf3 ("Merge tag 'for-6.0/dm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b86f4b790c998afdbc88fe1aa55cfe89c4068726 Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <[email protected]>
Date: Tue, 5 Dec 2023 16:39:16 +0100
Subject: [PATCH] dm-integrity: don't modify bio's immutable bio_vec in
integrity_metadata()

__bio_for_each_segment assumes that the first struct bio_vec argument doesn't change - it calls "bio_advance_iter_single((bio), &(iter), (bvl).bv_len)" to advance the iterator. Unfortunately, the dm-integrity code changes the bio_vec with "bv.bv_len -= pos". When this code path is taken, the iterator would be out of sync and dm-integrity would report errors. This happens if the machine is out of memory and "kmalloc" fails.

Fix this bug by making a copy of "bv" and changing the copy instead.

index e85c688fd91e..c5f03aab4552 100644
@@ -1755,11 +1755,12 @@ static void integrity_metadata(struct work_struct *w)
 		sectors_to_process = dio->range.n_sectors;
 
 		__bio_for_each_segment(bv, bio, iter, dio->bio_details.bi_iter) {
+			struct bio_vec bv_copy = bv;
 			unsigned int pos;
 			char *mem, *checksums_ptr;
 
 again:
-			mem = bvec_kmap_local(&bv);
+			mem = bvec_kmap_local(&bv_copy);
 			pos = 0;
 			checksums_ptr = checksums;
 			do {

@@ -1768,7 +1769,7 @@ static void integrity_metadata(struct work_struct *w)
 				sectors_to_process -= ic->sectors_per_block;
 				pos += ic->sectors_per_block << SECTOR_SHIFT;
 				sector += ic->sectors_per_block;
-			} while (pos < bv.bv_len && sectors_to_process && checksums != checksums_onstack);
+			} while (pos < bv_copy.bv_len && sectors_to_process && checksums != checksums_onstack);
 			kunmap_local(mem);
 
 			r = dm_integrity_rw_tag(ic, checksums, &dio->metadata_block, &dio->metadata_offset,

@@ -1793,9 +1794,9 @@ static void integrity_metadata(struct work_struct *w)
 			if (!sectors_to_process)
 				break;
 
-			if (unlikely(pos < bv.bv_len)) {
-				bv.bv_offset += pos;
-				bv.bv_len -= pos;
+			if (unlikely(pos < bv_copy.bv_len)) {
+				bv_copy.bv_offset += pos;
+				bv_copy.bv_len -= pos;
 				goto again;
 			}
 		}

Hi

Here I'm sending backport of the patch b86f4b790c998afdbc88fe1aa55cfe89c4068726 for the stable branches 4.19 to 5.15.

commit b86f4b790c998afdbc88fe1aa55cfe89c4068726

Author: Mikulas Patocka <[email protected]>
Date:   Tue Dec 5 16:39:16 2023 +0100

dm-integrity: don't modify bio's immutable bio_vec in integrity_metadata()

__bio_for_each_segment assumes that the first struct bio_vec argument doesn't change - it calls "bio_advance_iter_single((bio), &(iter), (bvl).bv_len)" to advance the iterator. Unfortunately, the dm-integrity code changes the bio_vec with "bv.bv_len -= pos". When this code path is taken, the iterator would be out of sync and dm-integrity would report errors. This happens if the machine is out of memory and "kmalloc" fails.

Fix this bug by making a copy of "bv" and changing the copy instead.

---
 drivers/md/dm-integrity.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

Index: linux-stable/drivers/md/dm-integrity.c
===================================================================
@@ -1762,11 +1762,12 @@ static void integrity_metadata(struct wo
 		sectors_to_process = dio->range.n_sectors;
 
 		__bio_for_each_segment(bv, bio, iter, dio->bio_details.bi_iter) {
+			struct bio_vec bv_copy = bv;
 			unsigned pos;
 			char *mem, *checksums_ptr;
 
 again:
-			mem = (char *)kmap_atomic(bv.bv_page) + bv.bv_offset;
+			mem = (char *)kmap_atomic(bv_copy.bv_page) + bv_copy.bv_offset;
 			pos = 0;
 			checksums_ptr = checksums;
 			do {

@@ -1775,7 +1776,7 @@ again:
 				sectors_to_process -= ic->sectors_per_block;
 				pos += ic->sectors_per_block << SECTOR_SHIFT;
 				sector += ic->sectors_per_block;
-			} while (pos < bv.bv_len && sectors_to_process && checksums != checksums_onstack);
+			} while (pos < bv_copy.bv_len && sectors_to_process && checksums != checksums_onstack);
 			kunmap_atomic(mem);
 
 			r = dm_integrity_rw_tag(ic, checksums, &dio->metadata_block, &dio->metadata_offset,

@@ -1796,9 +1797,9 @@ again:
 			if (!sectors_to_process)
 				break;
 
-			if (unlikely(pos < bv.bv_len)) {
-				bv.bv_offset += pos;
-				bv.bv_len -= pos;
+			if (unlikely(pos < bv_copy.bv_len)) {
+				bv_copy.bv_offset += pos;
+				bv_copy.bv_len -= pos;
 				goto again;
 			}
 		}