linux-ext4 - [PATCH] ext4: Fix buffer_head refcnt leak when ext4

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Message-Id: <1587618568-13418-1-git-send-email-xiyuyang19@fudan.edu.cn>
Date:   Thu, 23 Apr 2020 13:09:27 +0800
From:   Xiyu Yang <xiyuyang19@...an.edu.cn>
To:     "Theodore Ts'o" <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     yuanxzhang@...an.edu.cn, kjlu@....edu,
        Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>
Subject: [PATCH] ext4: Fix buffer_head refcnt leak when ext4_iget() fails

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

diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index f95ee99091e4..2e4729ba17e6 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -1234,6 +1234,7 @@ struct inode *ext4_orphan_get(struct super_block *sb, unsigned long ino)
 		ext4_set_errno(sb, -err);
 		ext4_error(sb, "couldn't read orphan inode %lu (err %d)",
 			   ino, err);
+		brelse(bitmap_bh);
 		return inode;
 	}

-- 
2.7.4