On Tue, Oct 30, 2018 at 5:03 AM Dave Chinner <david@xxxxxxxxxxxxx> wrote: > > On Mon, Oct 29, 2018 at 10:41:22AM -0400, Olga Kornievskaia wrote: > > On Sat, Oct 27, 2018 at 5:27 AM Dave Chinner <david@xxxxxxxxxxxxx> wrote: > > > > > > On Fri, Oct 26, 2018 at 04:10:48PM -0400, Olga Kornievskaia wrote: > > > > From: Olga Kornievskaia <kolga@xxxxxxxxxx> > > > > > > > > Input source offset can't be beyond the end of the file. > > > > > > > > Signed-off-by: Olga Kornievskaia <kolga@xxxxxxxxxx> > > > > --- > > > > fs/read_write.c | 3 +++ > > > > 1 file changed, 3 insertions(+) > > > > > > > > diff --git a/fs/read_write.c b/fs/read_write.c > > > > index fb4ffca..b3b304e 100644 > > > > --- a/fs/read_write.c > > > > +++ b/fs/read_write.c > > > > @@ -1594,6 +1594,9 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in, > > > > } > > > > } > > > > > > > > + if (pos_in >= i_size_read(inode_in)) > > > > + return -EINVAL; > > > > + > > > > > > vfs_copy_file_range seems ot be missing a wide range of checks. > > > rlimit, s_maxbytes, LFS file sizes, etc. This is a write, so all the > > > checks in generic_write_checks() apply, right? And the same security > > > issues like stripping setuid bits, etc? And we need to touch > > > atime on the source file, too? > > > > Yes sound like needed checks. > > > > > We've just merged 5 or so patches in 4.19-rc8 and we're ready to > > > merge another ~30 patch series to fix all the stuff missing from the > > > clone/dedupe file range operations that make them safe and robust. > > > It seems like copy_file_range is all the checks it needs, too? > > > > Are you proposing to not do this check now in favor of the proper work > > that will do all of those checks you listed above? > > No, I'm saying that if you're adding one check, there's a whole heap > of checks that still need to be added, *especially* if this is going > to fall back to page cache copy between superblocks that may have > different limits and constraints. > > There's security issues in this API. They need to be fixed before we > allow it to do more and potentially expose more problems due to it's > wider capability. Before I totally give up on this feature, can you help me understand your concerns with allowing the generic copy_file_range via do_splice(). I have mentioned I'm not a VFS expert thus I come from just looking at the available documentation and the code. I don't see any restrictions on the files being passed in the do_splice_direct(). There are no restrictions that they must be from the same filesystem or file system type. But perhaps this not the concern you had but more about checking validity of arguments? I have looked at Dave Wong's, if I'm not mistaken these 2 are the relevant patches: [PATCH 02/28] vfs: check file ranges before cloning files -- a couple but not all checks apply to copy_file_range() . specifically, the offsets don't wrap and offset isn't past eof (as my patch suggests). Other checks have to do with aligned memory which I don't believe is needed or other dedup requirement that don't apply. [PATCH 04/28] vfs: strengthen checking of file range inputs to generic_remap_checks -- these checks apply to the code once we fall back to the do_splice(). it looks to me that perhaps exporting generic_access_check_limits()/generic_write_check_limits so that they can be used by the copy_file_range when it get pulled in. Also, can you elaborate one what "security issues" are present in this API? Is it "stripping setuid bits" and so something like calling file_remove_priv() that should be done when the fallback to the do_splice_direct() happens? As for the atime, wouldn't the ->copy_file_range() be updating the file attributes? I guess for the fallback case, the attributes need to be updated. If those are checks/issues needed to be addressed and would then get the generic copy_file_range() in, I could give a go at a patch (or 2). > > > I can not volunteer > > to provide this comprehensive check. > > Why not? > > Cheers, > > Dave. > -- > Dave Chinner > david@xxxxxxxxxxxxx
