On Wed, Mar 09, 2022 at 08:31:09PM -0800, Eric Biggers wrote: > On Tue, Mar 08, 2022 at 10:50:43AM -0800, Darrick J. Wong wrote: > > From: Darrick J. Wong <djwong@xxxxxxxxxx> > > > > 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, collapse, insert 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. > > > > Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx> > > --- > > fs/ext4/ext4.h | 2 +- > > fs/ext4/extents.c | 32 +++++++++++++++++++++++++------- > > fs/ext4/inode.c | 7 ++++++- > > 3 files changed, 32 insertions(+), 9 deletions(-) > > Is there a test in xfstests that tests for this? Not currently. I /do/ actually have one drafted (which I'll email out as a reply) but I was gonna tackle fixing btrfs before I actually submit it to Eryu for upstream fstests. --D > - Eric
