From: Darrick J. Wong djwong@kernel.org
[ Upstream commit 05fd9564e9faf0f23b4676385e27d9405cef6637 ]
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: Filipe Manana fdmanana@suse.com Signed-off-by: Darrick J. Wong djwong@kernel.org Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/btrfs/file.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index a0179cc62913..28ddd9cf2069 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -2918,8 +2918,9 @@ int btrfs_replace_file_extents(struct btrfs_inode *inode, 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; @@ -2951,6 +2952,10 @@ 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; @@ -3391,7 +3396,7 @@ 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 @@ -3413,6 +3418,10 @@ 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