On Wed, Apr 17, 2019 at 12:04:33PM -0700, Darrick J. Wong wrote: > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > > The chattr manpage has this to say about immutable files: > > "A file with the 'i' attribute cannot be modified: it cannot be deleted > or renamed, no link can be created to this file, most of the file's > metadata can not be modified, and the file can not be opened in write > mode." > > Once the flag is set, it is enforced for quite a few file operations, > such as fallocate, fpunch, fzero, rm, touch, open, etc. However, we > don't check for immutability when doing a write(), a PROT_WRITE mmap(), > a truncate(), or a write to a previously established mmap. > > If a program has an open write fd to a file that the administrator > subsequently marks immutable, the program still can change the file > contents. Weird! > > The ability to write to an immutable file does not follow the manpage > promise that immutable files cannot be modified. Worse yet it's > inconsistent with the behavior of other syscalls which don't allow > modifications of immutable files. > > Therefore, add the necessary checks to make the write, mmap, and > truncate behavior consistent with what the manpage says and consistent > with other syscalls on filesystems which support IMMUTABLE. > > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> Thanks, looks good. I'm going to take this patch through the ext4 tree since it doesn't have any dependencies on the rest of the patch series. - Ted
