linux-kernel - [PATCH 5.7 281/376] ext4: fix buffer_head refcnt leak when ext4

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Date:   Fri, 19 Jun 2020 16:33:19 +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, Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>, stable@...nel.org,
        Theodore Tso <tytso@....edu>
Subject: [PATCH 5.7 281/376] ext4: fix buffer_head refcnt leak when ext4_iget() fails

From: Xiyu Yang <xiyuyang19@...an.edu.cn>

commit 3bbd0ef26098d241dc59ee77ba14b7dab0df0786 upstream.

ext4_orphan_get() invokes ext4_read_inode_bitmap(), which returns a
reference of the specified buffer_head object to "bitmap_bh" with
increased refcnt.

When ext4_orphan_get() returns, local variable "bitmap_bh" becomes
invalid, so the refcount should be decreased to keep refcount balanced.

The reference counting issue happens in one exception handling path of
ext4_orphan_get(). When ext4_iget() fails, the function forgets to
decrease the refcnt increased by ext4_read_inode_bitmap(), causing a
refcnt leak.

Fix this issue by calling brelse() when ext4_iget() fails.

Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
Cc: stable@...nel.org
Link: https://lore.kernel.org/r/1587618568-13418-1-git-send-email-xiyuyang19@fudan.edu.cn
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/ext4/ialloc.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -1246,6 +1246,7 @@ struct inode *ext4_orphan_get(struct sup
 		ext4_error_err(sb, -err,
 			       "couldn't read orphan inode %lu (err %d)",
 			       ino, err);
+		brelse(bitmap_bh);
 		return inode;
 	}