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Message-ID: <YjyGToTy8cHtytun@mit.edu> Date: Thu, 24 Mar 2022 10:55:10 -0400 From: "Theodore Ts'o" <tytso@....edu> To: "Darrick J. Wong" <djwong@...nel.org> Cc: linux-ext4 <linux-ext4@...r.kernel.org> Subject: Re: [PATCH] ext4: fix fallocate to use file_modified to update permissions consistently On Tue, Mar 08, 2022 at 10:50:43AM -0800, Darrick J. Wong wrote: > From: Darrick J. Wong <djwong@...nel.org> > > 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@...nel.org> Applied, thanks! (BTW, when you reply to a patch with a different patch, such as in this case, "fstests: ensure we drop suid after fallocate", it hopelessly confuses b4, which is why I'm sending this notification manually. Try running "b4 am 20220308185043.GA117678@...nolia" and compare that to https://lore.kernel.org/r/20220308185043.GA117678@magnolia and you'll see what I mean.) - Ted
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