From: Omar Sandoval <osan...@fb.com>

In btrfs_clone_files(), we must check the NODATASUM flag while the
inodes are locked. Otherwise, it's possible that btrfs_ioctl_setflags()
will change the flags after we check and we can end up with a party
checksummed file.

Fixes: 0e7b824c4ef9 ("Btrfs: don't make a file partly checksummed through file 
clone")
Signed-off-by: Omar Sandoval <osan...@fb.com>
---
 fs/btrfs/ioctl.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index cf0d3bc6f625..784e267aad32 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4280,11 +4280,6 @@ static noinline int btrfs_clone_files(struct file *file, 
struct file *file_src,
            src->i_sb != inode->i_sb)
                return -EXDEV;
 
-       /* don't make the dst file partly checksummed */
-       if ((BTRFS_I(src)->flags & BTRFS_INODE_NODATASUM) !=
-           (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM))
-               return -EINVAL;
-
        if (S_ISDIR(src->i_mode) || S_ISDIR(inode->i_mode))
                return -EISDIR;
 
@@ -4294,6 +4289,13 @@ static noinline int btrfs_clone_files(struct file *file, 
struct file *file_src,
                inode_lock(src);
        }
 
+       /* don't make the dst file partly checksummed */
+       if ((BTRFS_I(src)->flags & BTRFS_INODE_NODATASUM) !=
+           (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
+               ret = -EINVAL;
+               goto out_unlock;
+       }
+
        /* determine range to clone */
        ret = -EINVAL;
        if (off + len > src->i_size || off + len < off)
-- 
2.17.0

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