Commit 7d4d4f3b668d for kernel

commit 7d4d4f3b668d708d94f62ecdd33ac330a6fd8a84
Author: Mikulas Patocka <mpatocka@redhat.com>
Date:   Wed Sep 2 16:36:26 2026 +0200

    dm-integrity: fix NULL pointer dereference when the 'R' flag is used

    If the dm-integrity device has the SB_FLAG_DIRTY_BITMAP flag set and the
    user activates the device in the 'R' mode, a crash in dm_integrity_resume
    happens because the function attempts to read the journal containing the
    bitmap.

    This patch makes dm-integrity skip any writes to the device in
    dm_integrity_resume if the device is activated in the 'R' mode.

    Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
    Fixes: 468dfca38b1a ("dm integrity: add a bitmap mode")
    Cc: stable@vger.kernel.org

diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c
index 5327d7c6a71c..92970e12267a 100644
--- a/drivers/md/dm-integrity.c
+++ b/drivers/md/dm-integrity.c
@@ -3875,6 +3875,10 @@ static void dm_integrity_resume(struct dm_target *ti)
 	r = sync_rw_sb(ic, REQ_OP_READ);
 	if (r)
 		dm_integrity_io_error(ic, "reading superblock", r);
+
+	if (ic->mode == 'R')
+		goto skip_writes;
+
 	if ((ic->sb->flags & flags) != flags) {
 		ic->sb->flags |= flags;
 		r = sync_rw_sb(ic, REQ_OP_WRITE | REQ_FUA);
@@ -3984,6 +3988,7 @@ static void dm_integrity_resume(struct dm_target *ti)
 		}
 	}

+skip_writes:
 	ic->reboot_notifier.notifier_call = dm_integrity_reboot;
 	ic->reboot_notifier.next = NULL;
 	ic->reboot_notifier.priority = INT_MAX - 1;	/* be notified after md and before hardware drivers */