| Message ID | 20230317171309.73607-1-jlayton@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,1/2] nfsd: don't replace page in rq_pages if it's a continuation of last page | expand |
> On Mar 17, 2023, at 1:13 PM, Jeff Layton <jlayton@kernel.org> wrote: > > The splice read calls nfsd_splice_actor to put the pages containing file > data into the svc_rqst->rq_pages array. It's possible however to get a > splice result that only has a partial page at the end, if (e.g.) the > filesystem hands back a short read that doesn't cover the whole page. > > nfsd_splice_actor will plop the partial page into its rq_pages array and > return. Then later, when nfsd_splice_actor is called again, the > remainder of the page may end up being filled out. At this point, > nfsd_splice_actor will put the page into the array _again_ corrupting > the reply. If this is done enough times, rq_next_page will overrun the > array and corrupt the trailing fields -- the rq_respages and > rq_next_page pointers themselves. > > If we've already added the page to the array in the last pass, don't add > it to the array a second time when dealing with a splice continuation. > This was originally handled properly in nfsd_splice_actor, but commit > 91e23b1c3982 removed the check for it. > > Fixes: 91e23b1c3982 ("NFSD: Clean up nfsd_splice_actor()") > Cc: Al Viro <viro@zeniv.linux.org.uk> > Reported-by: Dario Lesca <d.lesca@solinos.it> > Tested-by: David Critch <dcritch@redhat.com> > Link: https://bugzilla.redhat.com/show_bug.cgi?id=2150630 > Signed-off-by: Jeff Layton <jlayton@kernel.org> I've applied this one internally for due-diligence testing. I'll wait a couple of days for review comments, so it's not likely to make v6.3-rc3 on Sunday. > --- > fs/nfsd/vfs.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c > index 502e1b7742db..97b38b47c563 100644 > --- a/fs/nfsd/vfs.c > +++ b/fs/nfsd/vfs.c > @@ -941,8 +941,14 @@ nfsd_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf, > struct page *last_page; > > last_page = page + (offset + sd->len - 1) / PAGE_SIZE; > - for (page += offset / PAGE_SIZE; page <= last_page; page++) > - svc_rqst_replace_page(rqstp, page); > + for (page += offset / PAGE_SIZE; page <= last_page; page++) { > + /* > + * Skip page replacement when extending the contents > + * of the current page. > + */ > + if (page != *(rqstp->rq_next_page - 1)) > + svc_rqst_replace_page(rqstp, page); > + } > if (rqstp->rq_res.page_len == 0) // first call > rqstp->rq_res.page_base = offset % PAGE_SIZE; > rqstp->rq_res.page_len += sd->len; > -- > 2.39.2 > -- Chuck Lever
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index 502e1b7742db..97b38b47c563 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -941,8 +941,14 @@ nfsd_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf, struct page *last_page; last_page = page + (offset + sd->len - 1) / PAGE_SIZE; - for (page += offset / PAGE_SIZE; page <= last_page; page++) - svc_rqst_replace_page(rqstp, page); + for (page += offset / PAGE_SIZE; page <= last_page; page++) { + /* + * Skip page replacement when extending the contents + * of the current page. + */ + if (page != *(rqstp->rq_next_page - 1)) + svc_rqst_replace_page(rqstp, page); + } if (rqstp->rq_res.page_len == 0) // first call rqstp->rq_res.page_base = offset % PAGE_SIZE; rqstp->rq_res.page_len += sd->len;
The splice read calls nfsd_splice_actor to put the pages containing file data into the svc_rqst->rq_pages array. It's possible however to get a splice result that only has a partial page at the end, if (e.g.) the filesystem hands back a short read that doesn't cover the whole page. nfsd_splice_actor will plop the partial page into its rq_pages array and return. Then later, when nfsd_splice_actor is called again, the remainder of the page may end up being filled out. At this point, nfsd_splice_actor will put the page into the array _again_ corrupting the reply. If this is done enough times, rq_next_page will overrun the array and corrupt the trailing fields -- the rq_respages and rq_next_page pointers themselves. If we've already added the page to the array in the last pass, don't add it to the array a second time when dealing with a splice continuation. This was originally handled properly in nfsd_splice_actor, but commit 91e23b1c3982 removed the check for it. Fixes: 91e23b1c3982 ("NFSD: Clean up nfsd_splice_actor()") Cc: Al Viro <viro@zeniv.linux.org.uk> Reported-by: Dario Lesca <d.lesca@solinos.it> Tested-by: David Critch <dcritch@redhat.com> Link: https://bugzilla.redhat.com/show_bug.cgi?id=2150630 Signed-off-by: Jeff Layton <jlayton@kernel.org> --- fs/nfsd/vfs.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)