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From:   linan666@huaweicloud.com
To:     song@kernel.org, bingjingc@synology.com, allenpeng@synology.com,
        shli@fb.com, alexwu@synology.com, neilb@suse.de
Cc:     linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org,
        linan122@huawei.com, yukuai3@huawei.com, yi.zhang@huawei.com,
        houtao1@huawei.com, yangerkun@huawei.com
Subject: [PATCH v3 1/4] md/raid10: fix null-ptr-deref of mreplace in raid10_sync_request
Date:   Sat, 27 May 2023 15:22:15 +0800
Message-Id: <20230527072218.2365857-2-linan666@huaweicloud.com>
In-Reply-To: <20230527072218.2365857-1-linan666@huaweicloud.com>
References: <20230527072218.2365857-1-linan666@huaweicloud.com>
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From: Li Nan <linan122@huawei.com>

There are two check of 'mreplace' in raid10_sync_request(). In the first
check, 'need_replace' will be set and 'mreplace' will be used later if
no-Faulty 'mreplace' exists, In the second check, 'mreplace' will be
set to NULL if it is Faulty, but 'need_replace' will not be changed
accordingly. null-ptr-deref occurs if Faulty is set between two check.

Fix it by merging two checks into one. And replace 'need_replace' with
'mreplace' because their values are always the same.

Fixes: ee37d7314a32 ("md/raid10: Fix raid10 replace hang when new added disk faulty")
Signed-off-by: Li Nan <linan122@huawei.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
---
 drivers/md/raid10.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 4fcfcb350d2b..0acb4c103c10 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -3438,7 +3438,6 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 			int must_sync;
 			int any_working;
 			int need_recover = 0;
-			int need_replace = 0;
 			struct raid10_info *mirror = &conf->mirrors[i];
 			struct md_rdev *mrdev, *mreplace;
 
@@ -3450,11 +3449,10 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 			    !test_bit(Faulty, &mrdev->flags) &&
 			    !test_bit(In_sync, &mrdev->flags))
 				need_recover = 1;
-			if (mreplace != NULL &&
-			    !test_bit(Faulty, &mreplace->flags))
-				need_replace = 1;
+			if (mreplace && test_bit(Faulty, &mreplace->flags))
+				mreplace = NULL;
 
-			if (!need_recover && !need_replace) {
+			if (!need_recover && !mreplace) {
 				rcu_read_unlock();
 				continue;
 			}
@@ -3470,8 +3468,6 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 				rcu_read_unlock();
 				continue;
 			}
-			if (mreplace && test_bit(Faulty, &mreplace->flags))
-				mreplace = NULL;
 			/* Unless we are doing a full sync, or a replacement
 			 * we only need to recover the block if it is set in
 			 * the bitmap
@@ -3594,11 +3590,11 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 				bio = r10_bio->devs[1].repl_bio;
 				if (bio)
 					bio->bi_end_io = NULL;
-				/* Note: if need_replace, then bio
+				/* Note: if replace is not NULL, then bio
 				 * cannot be NULL as r10buf_pool_alloc will
 				 * have allocated it.
 				 */
-				if (!need_replace)
+				if (!mreplace)
 					break;
 				bio->bi_next = biolist;
 				biolist = bio;
-- 
2.31.1