[PATCH v2] Check for immutable flag in fallocate path

[Marco Stornelli]

From: Marco Stornelli <marco.stornelli@xxxxxxxxx>

All fs must check for the immutable flag in their fallocate callback.
It's possible to have a race condition in this scenario: an application
open a file in read/write and it does something, meanwhile root set the
immutable flag on the file, the application at that point can call
fallocate with success. Only Ocfs2 check for the immutable flag at the
moment.

Signed-off-by: Marco Stornelli <marco.stornelli@xxxxxxxxx>
---
Patch is against 2.6.38-rc5

ChangeLog
v2: Added the check for append-only file for XFS
v1: First draft

--- linux-2.6.38-rc5-orig/fs/ext4/extents.c	2011-02-16 04:23:45.000000000 +0100
+++ linux-2.6.38-rc5/fs/ext4/extents.c	2011-02-21 08:43:37.000000000 +0100
@@ -3670,6 +3670,12 @@ long ext4_fallocate(struct file *file, i
 	 */
 	credits = ext4_chunk_trans_blocks(inode, max_blocks);
 	mutex_lock(&inode->i_mutex);
+
+	if (IS_IMMUTABLE(inode)) {
+		mutex_unlock(&inode->i_mutex);
+		return -EPERM;
+	}
+
 	ret = inode_newsize_ok(inode, (len + offset));
 	if (ret) {
 		mutex_unlock(&inode->i_mutex);
--- linux-2.6.38-rc5-orig/fs/btrfs/file.c	2011-02-16 04:23:45.000000000 +0100
+++ linux-2.6.38-rc5/fs/btrfs/file.c	2011-02-21 08:55:58.000000000 +0100
@@ -1289,6 +1289,12 @@ static long btrfs_fallocate(struct file
 	btrfs_wait_ordered_range(inode, alloc_start, alloc_end - alloc_start);
 
 	mutex_lock(&inode->i_mutex);
+
+	if (IS_IMMUTABLE(inode)) {
+		ret = -EPERM;
+		goto out;
+	}
+
 	ret = inode_newsize_ok(inode, alloc_end);
 	if (ret)
 		goto out;
--- linux-2.6.38-rc5-orig/fs/gfs2/file.c	2011-02-16 04:23:45.000000000 +0100
+++ linux-2.6.38-rc5/fs/gfs2/file.c	2011-02-21 09:09:17.000000000 +0100
@@ -797,6 +797,11 @@ static long gfs2_fallocate(struct file *
 	if (unlikely(error))
 		goto out_uninit;
 
+	if (IS_IMMUTABLE(inode)) {
+		error = -EPERM;
+		goto out_unlock;
+	}
+
 	if (!gfs2_write_alloc_required(ip, offset, len))
 		goto out_unlock;
 
--- ./linux-2.6.38-rc5/fs/xfs/linux-2.6/xfs_file.c	2011-02-16 04:23:45.000000000 +0100
+++ ./linux-2.6.38-rc5/fs/xfs/linux-2.6/xfs_file.c	2011-03-03 09:25:32.000000000 +0100
@@ -906,8 +906,18 @@ xfs_file_fallocate(
 
 	xfs_ilock(ip, XFS_IOLOCK_EXCL);
 
-	if (mode & FALLOC_FL_PUNCH_HOLE)
+	if (mode & FALLOC_FL_PUNCH_HOLE) {
 		cmd = XFS_IOC_UNRESVSP;
+		if (IS_APPEND(inode)) {
+			error = -EPERM;
+			goto out_unlock;
+		}
+	}
+
+	if (IS_IMMUTABLE(inode)) {
+		error = -EPERM;
+		goto out_unlock;
+	}
 
 	/* check the new inode size is valid before allocating */
 	if (!(mode & FALLOC_FL_KEEP_SIZE) &&
--
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