On Fri, Oct 5, 2018 at 3:46 AM Darrick J. Wong <darrick.wong@xxxxxxxxxx> wrote:
>
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> Clone range is an optimization on a regular file write. File writes
> that extend the file length are subject to various constraints which are
> not checked by clonerange. This is a correctness problem, because we're
> never allowed to touch ranges that the page cache can't support
> (s_maxbytes); we're not supposed to deal with large offsets
> (MAX_NON_LFS) if O_LARGEFILE isn't set; and we must obey resource limits
> (RLIMIT_FSIZE).
>
> Therefore, add these checks to the new generic_clone_checks function so
> that we curtail unexpected behavior.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> mm/filemap.c | 31 +++++++++++++++++++++++++++++++
> 1 file changed, 31 insertions(+)
>
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 68ec91d05c7b..f74391721234 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -3015,6 +3015,37 @@ int generic_clone_checks(struct file *file_in, loff_t pos_in,
> return -EINVAL;
> count = min(count, size_in - (uint64_t)pos_in);
>
> + /* Don't exceed RLMIT_FSIZE in the file we're writing into. */
> + if (limit != RLIM_INFINITY) {
> + if (pos_out >= limit) {
> + send_sig(SIGXFSZ, current, 0);
> + return -EFBIG;
> + }
> + count = min(count, limit - (uint64_t)pos_out);
> + }
> +
> + /* Don't exceed the LFS limits. */
> + if (unlikely(pos_out + count > MAX_NON_LFS &&
> + !(file_out->f_flags & O_LARGEFILE))) {
> + if (pos_out >= MAX_NON_LFS)
> + return -EFBIG;
> + count = min(count, MAX_NON_LFS - (uint64_t)pos_out);
> + }
> + if (unlikely(pos_in + count > MAX_NON_LFS &&
> + !(file_in->f_flags & O_LARGEFILE))) {
> + if (pos_in >= MAX_NON_LFS)
> + return -EFBIG;
> + count = min(count, MAX_NON_LFS - (uint64_t)pos_in);
> + }
> +
> + /* Don't operate on ranges the page cache doesn't support. */
> + if (unlikely(pos_out >= inode_out->i_sb->s_maxbytes ||
> + pos_in >= inode_in->i_sb->s_maxbytes))
> + return -EFBIG;
> +
Forget my standards, this doesn't abide by your own standards ;-)
Please factor out generic_write_checks() and use it instead of
duplicating the code. The in/out variant doesn't justify not calling
the helper twice IMO.
Thanks,
Amir.
