Patch "md/raid10: fix null-ptr-deref in raid10_sync_request" has been added to the 4.19-stable tree

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This is a note to let you know that I've just added the patch titled

    md/raid10: fix null-ptr-deref in raid10_sync_request

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     md-raid10-fix-null-ptr-deref-in-raid10_sync_request.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From a405c6f0229526160aa3f177f65e20c86fce84c5 Mon Sep 17 00:00:00 2001
From: Li Nan <linan122@xxxxxxxxxx>
Date: Wed, 22 Feb 2023 12:10:00 +0800
Subject: md/raid10: fix null-ptr-deref in raid10_sync_request

From: Li Nan <linan122@xxxxxxxxxx>

commit a405c6f0229526160aa3f177f65e20c86fce84c5 upstream.

init_resync() inits mempool and sets conf->have_replacemnt at the beginning
of sync, close_sync() frees the mempool when sync is completed.

After [1] recovery might be skipped and init_resync() is called but
close_sync() is not. null-ptr-deref occurs with r10bio->dev[i].repl_bio.

The following is one way to reproduce the issue.

  1) create a array, wait for resync to complete, mddev->recovery_cp is set
     to MaxSector.
  2) recovery is woken and it is skipped. conf->have_replacement is set to
     0 in init_resync(). close_sync() not called.
  3) some io errors and rdev A is set to WantReplacement.
  4) a new device is added and set to A's replacement.
  5) recovery is woken, A have replacement, but conf->have_replacemnt is
     0. r10bio->dev[i].repl_bio will not be alloced and null-ptr-deref
     occurs.

Fix it by not calling init_resync() if recovery skipped.

[1] commit 7e83ccbecd60 ("md/raid10: Allow skipping recovery when clean arrays are assembled")
Fixes: 7e83ccbecd60 ("md/raid10: Allow skipping recovery when clean arrays are assembled")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Li Nan <linan122@xxxxxxxxxx>
Signed-off-by: Song Liu <song@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230222041000.3341651-3-linan666@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/md/raid10.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -2957,10 +2957,6 @@ static sector_t raid10_sync_request(stru
 	sector_t chunk_mask = conf->geo.chunk_mask;
 	int page_idx = 0;
 
-	if (!mempool_initialized(&conf->r10buf_pool))
-		if (init_resync(conf))
-			return 0;
-
 	/*
 	 * Allow skipping a full rebuild for incremental assembly
 	 * of a clean array, like RAID1 does.
@@ -2976,6 +2972,10 @@ static sector_t raid10_sync_request(stru
 		return mddev->dev_sectors - sector_nr;
 	}
 
+	if (!mempool_initialized(&conf->r10buf_pool))
+		if (init_resync(conf))
+			return 0;
+
  skipped:
 	max_sector = mddev->dev_sectors;
 	if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery) ||


Patches currently in stable-queue which might be from linan122@xxxxxxxxxx are

queue-4.19/md-raid10-fix-null-ptr-deref-in-raid10_sync_request.patch



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