From b5c40d598f5408bd0ca22dfffa82f03cd9433f23 Mon Sep 17 00:00:00 2001 From: Omar Sandoval Date: Tue, 22 May 2018 15:02:12 -0700 Subject: [PATCH] Btrfs: fix clone vs chattr NODATASUM race 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. The race window is only a few instructions in size, between the if and the locks which is: 3834 if (S_ISDIR(src->i_mode) || S_ISDIR(inode->i_mode)) 3835 return -EISDIR; where the setflags must be run and toggle the NODATASUM flag (provided the file size is 0). The clone will block on the inode lock, segflags takes the inode lock, changes flags, releases log and clone continues. Not impossible but still needs a lot of bad luck to hit unintentionally. Fixes: 0e7b824c4ef9 ("Btrfs: don't make a file partly checksummed through file clone") CC: stable@vger.kernel.org # 4.4+ Signed-off-by: Omar Sandoval Reviewed-by: Nikolay Borisov Reviewed-by: David Sterba [ update changelog ] Signed-off-by: David Sterba --- 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 743c4f1b8001..b9b779a4ab6e 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -3808,11 +3808,6 @@ 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; @@ -3822,6 +3817,13 @@ 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) -- 2.30.2