On Mon, Dec 3, 2018 at 3:34 AM Dave Chinner <david@xxxxxxxxxxxxx> wrote: > > From: Dave Chinner <dchinner@xxxxxxxxxx> > > before we can enable cross-device copies into copy_file_range(), > we have to ensure that ->remap_file_range() implemenations will > correctly reject attempts to do cross filesystem clones. Currently > these checks are done above calls to ->remap_file_range(), but > we need to drive them inwards so that we get EXDEV protection for all > callers of ->remap_file_range(). If there is no check before calling ->remap_file_range() then NFS barfs. Perhaps it needs a check internally that checks that both file handles are from the NFS but this was not needed before. Or there needs to the a check in VFS. > > Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx> > --- > fs/read_write.c | 21 +++++++++++++-------- > 1 file changed, 13 insertions(+), 8 deletions(-) > > diff --git a/fs/read_write.c b/fs/read_write.c > index 3288db1d5f21..174cf92eea1d 100644 > --- a/fs/read_write.c > +++ b/fs/read_write.c > @@ -1909,6 +1909,19 @@ int generic_remap_file_range_prep(struct file *file_in, loff_t pos_in, > bool same_inode = (inode_in == inode_out); > int ret; > > + /* > + * FICLONE/FICLONERANGE ioctls enforce that src and dest files are on > + * the same mount. Practically, they only need to be on the same file > + * system. We check this here rather than at the ioctl layers because > + * this is effectively a limitation of the fielsystem implementations, > + * not so much the API itself. Further, ->remap_file_range() can be > + * called from syscalls that don't have cross device copy restrictions > + * (such as copy_file_range()) and so we need to catch them before we > + * do any damage. > + */ > + if (inode_in->i_sb != inode_out->i_sb) > + return -EXDEV; > + > /* Don't touch certain kinds of inodes */ > if (IS_IMMUTABLE(inode_out)) > return -EPERM; > @@ -2013,14 +2026,6 @@ loff_t do_clone_file_range(struct file *file_in, loff_t pos_in, > if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode)) > return -EINVAL; > > - /* > - * FICLONE/FICLONERANGE ioctls enforce that src and dest files are on > - * the same mount. Practically, they only need to be on the same file > - * system. > - */ > - if (inode_in->i_sb != inode_out->i_sb) > - return -EXDEV; > - > if (!(file_in->f_mode & FMODE_READ) || > !(file_out->f_mode & FMODE_WRITE) || > (file_out->f_flags & O_APPEND)) > -- > 2.19.1 >
