linux-ext4 - [PATCH] ext4: Fix refcount leak bug in __ext4_new

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Date:   Wed,  8 Sep 2021 10:46:05 +0800
From:   Chenyuan Mi <cymi20@...an.edu.cn>
To:     unlisted-recipients:; (no To-header on input)
Cc:     yuanxzhang@...an.edu.cn, Chenyuan Mi <cymi20@...an.edu.cn>,
        Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>,
        "Theodore Ts'o" <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] ext4: Fix refcount leak bug in __ext4_new_inode()

After successfully creating handle by __ext4_journal_start_sb(),
the function forgets to decrease the refcount of handle in several
paths, causing refcount leak.

Fix this issue by recording a flag when successfully getting handle
by __ext4_journal_start_sb(), and decrease the refcount of handle
when exiting this function if holding the flag.

Signed-off-by: Chenyuan Mi <cymi20@...an.edu.cn>
Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>

---
 fs/ext4/ialloc.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index f73e5eb43eae..7563b892c64f 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -944,6 +944,7 @@ struct inode *__ext4_new_inode(struct user_namespace *mnt_userns,
 	ext4_group_t flex_group;
 	struct ext4_group_info *grp = NULL;
 	bool encrypt = false;
+	bool create_handle = false;
 
 	/* Cannot create files in a deleted directory */
 	if (!dir || !dir->i_nlink)
@@ -1085,6 +1086,7 @@ struct inode *__ext4_new_inode(struct user_namespace *mnt_userns,
 				ext4_std_error(sb, err);
 				goto out;
 			}
+			create_handle = true;
 		}
 		BUFFER_TRACE(inode_bitmap_bh, "get_write_access");
 		err = ext4_journal_get_write_access(handle, sb, inode_bitmap_bh,
@@ -1345,7 +1347,8 @@ struct inode *__ext4_new_inode(struct user_namespace *mnt_userns,
 		ext4_std_error(sb, err);
 		goto fail_free_drop;
 	}
-
+	if (create_handle)
+		ext4_journal_stop(handle);
 	ext4_debug("allocating inode %lu\n", inode->i_ino);
 	trace_ext4_allocate_inode(inode, dir, mode);
 	brelse(inode_bitmap_bh);
@@ -1357,6 +1360,8 @@ struct inode *__ext4_new_inode(struct user_namespace *mnt_userns,
 	clear_nlink(inode);
 	unlock_new_inode(inode);
 out:
+	if (create_handle)
+		ext4_journal_stop(handle);
 	dquot_drop(inode);
 	inode->i_flags |= S_NOQUOTA;
 	iput(inode);
-- 
2.17.1