Commit 217190dc authored by Darrick J. Wong's avatar Darrick J. Wong Committed by Greg Kroah-Hartman
Browse files

btrfs: fix fallocate to use file_modified to update permissions consistently 



[ Upstream commit 05fd9564 ]

Since the initial introduction of (posix) fallocate back at the turn of
the century, it has been possible to use this syscall to change the
user-visible contents of files.  This can happen by extending the file
size during a preallocation, or through any of the newer modes (punch,
zero range).  Because the call can be used to change file contents, we
should treat it like we do any other modification to a file -- update
the mtime, and drop set[ug]id privileges/capabilities.

The VFS function file_modified() does all this for us if pass it a
locked inode, so let's make fallocate drop permissions correctly.

Reviewed-by: default avatarFilipe Manana <fdmanana@suse.com>
Signed-off-by: default avatarDarrick J. Wong <djwong@kernel.org>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 9b5d1b34

fs/btrfs/file.c

+11 −2
Original line number Diff line number Diff line
@@ -2833,8 +2833,9 @@ int btrfs_replace_file_extents(struct inode *inode, struct btrfs_path *path, 
	return ret;

}



static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)

static int btrfs_punch_hole(struct file *file, loff_t offset, loff_t len)

{

	struct inode *inode = file_inode(file);

	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);

	struct btrfs_root *root = BTRFS_I(inode)->root;

	struct extent_state *cached_state = NULL;
@@ -2866,6 +2867,10 @@ static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len) 
		goto out_only_mutex;

	}



	ret = file_modified(file);

	if (ret)

		goto out_only_mutex;



	lockstart = round_up(offset, btrfs_inode_sectorsize(BTRFS_I(inode)));

	lockend = round_down(offset + len,

			     btrfs_inode_sectorsize(BTRFS_I(inode))) - 1;
@@ -3301,7 +3306,7 @@ static long btrfs_fallocate(struct file *file, int mode, 
		return -EOPNOTSUPP;



	if (mode & FALLOC_FL_PUNCH_HOLE)

		return btrfs_punch_hole(inode, offset, len);

		return btrfs_punch_hole(file, offset, len);



	/*

	 * Only trigger disk allocation, don't trigger qgroup reserve
@@ -3323,6 +3328,10 @@ static long btrfs_fallocate(struct file *file, int mode, 
			goto out;

	}



	ret = file_modified(file);

	if (ret)

		goto out;



	/*

	 * TODO: Move these two operations after we have checked

	 * accurate reserved space, or fallocate can still fail but