linux-kernel - [PATCH 3.10 074/139] ext4: avoid deadlock when expanding inode size

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Message-Id: <1509571600-4858-25-git-send-email-w@1wt.eu>
Date:   Wed,  1 Nov 2017 22:26:15 +0100
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Jan Kara <jack@...e.cz>, stable@...r.kernel.org#4.4.x,
        "Theodore Ts'o" <tytso@....edu>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 074/139] ext4: avoid deadlock when expanding inode size

From: Jan Kara <jack@...e.cz>

commit 2e81a4eeedcaa66e35f58b81e0755b87057ce392 upstream.

When we need to move xattrs into external xattr block, we call
ext4_xattr_block_set() from ext4_expand_extra_isize_ea(). That may end
up calling ext4_mark_inode_dirty() again which will recurse back into
the inode expansion code leading to deadlocks.

Protect from recursion using EXT4_STATE_NO_EXPAND inode flag and move
its management into ext4_expand_extra_isize_ea() since its manipulation
is safe there (due to xattr_sem) from possible races with
ext4_xattr_set_handle() which plays with it as well.

CC: stable@...r.kernel.org   # 4.4.x
Signed-off-by: Jan Kara <jack@...e.cz>
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Willy Tarreau <w@....eu>
---
 fs/ext4/inode.c |  2 --
 fs/ext4/xattr.c | 19 +++++++++++++------
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 1094017..26054c1 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5098,8 +5098,6 @@ int ext4_mark_inode_dirty(handle_t *handle, struct inode *inode)
 						      sbi->s_want_extra_isize,
 						      iloc, handle);
 			if (ret) {
-				ext4_set_inode_state(inode,
-						     EXT4_STATE_NO_EXPAND);
 				if (mnt_count !=
 					le16_to_cpu(sbi->s_es->s_mnt_count)) {
 					ext4_warning(inode->i_sb,
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 92850ba..dde00d1 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -1266,11 +1266,13 @@ int ext4_expand_extra_isize_ea(struct inode *inode, int new_extra_isize,
 	int s_min_extra_isize = le16_to_cpu(EXT4_SB(inode->i_sb)->s_es->s_min_extra_isize);
 
 	down_write(&EXT4_I(inode)->xattr_sem);
+	/*
+	 * Set EXT4_STATE_NO_EXPAND to avoid recursion when marking inode dirty
+	 */
+	ext4_set_inode_state(inode, EXT4_STATE_NO_EXPAND);
 retry:
-	if (EXT4_I(inode)->i_extra_isize >= new_extra_isize) {
-		up_write(&EXT4_I(inode)->xattr_sem);
-		return 0;
-	}
+	if (EXT4_I(inode)->i_extra_isize >= new_extra_isize)
+		goto out;
 
 	header = IHDR(inode, raw_inode);
 	entry = IFIRST(header);
@@ -1295,8 +1297,7 @@ retry:
 				(void *)header, total_ino,
 				inode->i_sb->s_blocksize);
 		EXT4_I(inode)->i_extra_isize = new_extra_isize;
-		error = 0;
-		goto cleanup;
+		goto out;
 	}
 
 	/*
@@ -1457,6 +1458,8 @@ retry:
 		kfree(bs);
 	}
 	brelse(bh);
+out:
+	ext4_clear_inode_state(inode, EXT4_STATE_NO_EXPAND);
 	up_write(&EXT4_I(inode)->xattr_sem);
 	return 0;
 
@@ -1468,6 +1471,10 @@ cleanup:
 	kfree(is);
 	kfree(bs);
 	brelse(bh);
+	/*
+	 * We deliberately leave EXT4_STATE_NO_EXPAND set here since inode
+	 * size expansion failed.
+	 */
 	up_write(&EXT4_I(inode)->xattr_sem);
 	return error;
 }
-- 
2.8.0.rc2.1.gbe9624a