[PATCH 6.1+] dm: fix improper splitting for abnormal bios

[Mike Snitzer <snitzer@kernel.org>]

From: Benjamin Marzinski <bmarzins@redhat.com>

Conflicts: Code changes due to missing upstream commit 86a3238c7b9b
           ('dm: change "unsigned" to "unsigned int"')

commit f7b58a69fad9d2c4c90cab0247811155dd0d48e7
Author: Mike Snitzer <snitzer@kernel.org>
Date:   Thu Mar 30 14:56:38 2023 -0400

    dm: fix improper splitting for abnormal bios

    "Abnormal" bios include discards, write zeroes and secure erase. By no
    longer passing the calculated 'len' pointer, commit 7dd06a2548b2 ("dm:
    allow dm_accept_partial_bio() for dm_io without duplicate bios") took a
    senseless approach to disallowing dm_accept_partial_bio() from working
    for duplicate bios processed using __send_duplicate_bios().

    It inadvertently and incorrectly stopped the use of 'len' when
    initializing a target's io (in alloc_tio). As such the resulting tio
    could address more area of a device than it should.

    For example, when discarding an entire DM striped device with the
    following DM table:
     vg-lvol0: 0 159744 striped 2 128 7:0 2048 7:1 2048
     vg-lvol0: 159744 45056 striped 2 128 7:2 2048 7:3 2048

    Before this fix:

     device-mapper: striped: target_stripe=0, bdev=7:0, start=2048 len=102400
     blkdiscard: attempt to access beyond end of device
     loop0: rw=2051, sector=2048, nr_sectors = 102400 limit=81920

     device-mapper: striped: target_stripe=1, bdev=7:1, start=2048 len=102400
     blkdiscard: attempt to access beyond end of device
     loop1: rw=2051, sector=2048, nr_sectors = 102400 limit=81920

    After this fix;

     device-mapper: striped: target_stripe=0, bdev=7:0, start=2048 len=79872
     device-mapper: striped: target_stripe=1, bdev=7:1, start=2048 len=79872

    Fixes: 7dd06a2548b2 ("dm: allow dm_accept_partial_bio() for dm_io without duplicate bios")
    Cc: stable@vger.kernel.org
    Reported-by: Orange Kao <orange@aiven.io>
    Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
---
 drivers/md/dm.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index f9a402c04666..e624a919fe55 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1460,7 +1460,8 @@ static void setup_split_accounting(struct clone_info *ci, unsigned len)
 }
 
 static void alloc_multiple_bios(struct bio_list *blist, struct clone_info *ci,
-				struct dm_target *ti, unsigned num_bios)
+				struct dm_target *ti, unsigned num_bios,
+				unsigned *len)
 {
 	struct bio *bio;
 	int try;
@@ -1471,7 +1472,7 @@ static void alloc_multiple_bios(struct bio_list *blist, struct clone_info *ci,
 		if (try)
 			mutex_lock(&ci->io->md->table_devices_lock);
 		for (bio_nr = 0; bio_nr < num_bios; bio_nr++) {
-			bio = alloc_tio(ci, ti, bio_nr, NULL,
+			bio = alloc_tio(ci, ti, bio_nr, len,
 					try ? GFP_NOIO : GFP_NOWAIT);
 			if (!bio)
 				break;
@@ -1507,7 +1508,7 @@ static int __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti,
 		break;
 	default:
 		/* dm_accept_partial_bio() is not supported with shared tio->len_ptr */
-		alloc_multiple_bios(&blist, ci, ti, num_bios);
+		alloc_multiple_bios(&blist, ci, ti, num_bios, len);
 		while ((clone = bio_list_pop(&blist))) {
 			dm_tio_set_flag(clone_to_tio(clone), DM_TIO_IS_DUPLICATE_BIO);
 			__map_bio(clone);
-- 
2.30.0