linux-kernel - [PATCH 5.17 0884/1126] btrfs: do not clean up repair bio if submit fails

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Date:   Tue,  5 Apr 2022 09:27:11 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Boris Burkov <boris@....io>,
        Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.17 0884/1126] btrfs: do not clean up repair bio if submit fails

From: Josef Bacik <josef@...icpanda.com>

[ Upstream commit 8cbc3001a3264d998d6b6db3e23f935c158abd4d ]

The submit helper will always run bio_endio() on the bio if it fails to
submit, so cleaning up the bio just leads to a variety of use-after-free
and NULL pointer dereference bugs because we race with the endio
function that is cleaning up the bio.  Instead just return BLK_STS_OK as
the repair function has to continue to process the rest of the pages,
and the endio for the repair bio will do the appropriate cleanup for the
page that it was given.

Reviewed-by: Boris Burkov <boris@....io>
Signed-off-by: Josef Bacik <josef@...icpanda.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/btrfs/extent_io.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index f767c1164742..99028984340a 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2639,7 +2639,6 @@ int btrfs_repair_one_sector(struct inode *inode,
 	const int icsum = bio_offset >> fs_info->sectorsize_bits;
 	struct bio *repair_bio;
 	struct btrfs_bio *repair_bbio;
-	blk_status_t status;
 
 	btrfs_debug(fs_info,
 		   "repair read error: read error at %llu", start);
@@ -2678,13 +2677,13 @@ int btrfs_repair_one_sector(struct inode *inode,
 		    "repair read error: submitting new read to mirror %d",
 		    failrec->this_mirror);
 
-	status = submit_bio_hook(inode, repair_bio, failrec->this_mirror,
-				 failrec->bio_flags);
-	if (status) {
-		free_io_failure(failure_tree, tree, failrec);
-		bio_put(repair_bio);
-	}
-	return blk_status_to_errno(status);
+	/*
+	 * At this point we have a bio, so any errors from submit_bio_hook()
+	 * will be handled by the endio on the repair_bio, so we can't return an
+	 * error here.
+	 */
+	submit_bio_hook(inode, repair_bio, failrec->this_mirror, failrec->bio_flags);
+	return BLK_STS_OK;
 }
 
 static void end_page_read(struct page *page, bool uptodate, u64 start, u32 len)
-- 
2.34.1