David Howells
2023-Feb-27 15:51 UTC
[RFC][PATCH v2] splice: Prevent gifting of multipage folios
Don't let parts of compound pages/multipage folios be gifted by (vm)splice
into a pipe as the other end may only be expecting single-page gifts (fuse
and virtio console for example).
replace_page_cache_folio(), for example, will do the wrong thing if it
tries to replace a single paged folio with a multipage folio.
Try to avoid this by making add_to_pipe() remove the gift flag on multipage
folios.
Fixes: 7afa6fd037e5 ("[PATCH] vmsplice: allow user to pass in gift
pages")
Signed-off-by: David Howells <dhowells at redhat.com>
cc: Matthew Wilcox <willy at infradead.org>
cc: Jens Axboe <axboe at suse.de>
cc: Miklos Szeredi <miklos at szeredi.hu>
cc: Amit Shah <amit at kernel.org>
cc: linux-fsdevel at vger.kernel.org
cc: virtualization at lists.linux-foundation.org
cc: linux-mm at kvack.org
---
fs/splice.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/splice.c b/fs/splice.c
index 2e76dbb81a8f..8bbd7794d9f0 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -240,6 +240,8 @@ ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct
pipe_buffer *buf)
} else if (pipe_full(head, tail, pipe->max_usage)) {
ret = -EAGAIN;
} else {
+ if (PageCompound(buf->page))
+ buf->flags &= ~PIPE_BUF_FLAG_GIFT;
pipe->bufs[head & mask] = *buf;
pipe->head = head + 1;
return buf->len;
Matthew Wilcox
2023-Feb-27 15:53 UTC
[RFC][PATCH v2] splice: Prevent gifting of multipage folios
On Mon, Feb 27, 2023 at 03:51:03PM +0000, David Howells wrote:> > Don't let parts of compound pages/multipage folios be gifted by (vm)splice > into a pipe as the other end may only be expecting single-page gifts (fuse > and virtio console for example). > > replace_page_cache_folio(), for example, will do the wrong thing if it > tries to replace a single paged folio with a multipage folio. > > Try to avoid this by making add_to_pipe() remove the gift flag on multipage > folios. > > Fixes: 7afa6fd037e5 ("[PATCH] vmsplice: allow user to pass in gift pages") > Signed-off-by: David Howells <dhowells at redhat.com> > cc: Matthew Wilcox <willy at infradead.org>Reviewed-by: Matthew Wilcox (Oracle) <willy at infradead.org> Cc: stable at vger.kernel.org> cc: Jens Axboe <axboe at suse.de> > cc: Miklos Szeredi <miklos at szeredi.hu> > cc: Amit Shah <amit at kernel.org> > cc: linux-fsdevel at vger.kernel.org > cc: virtualization at lists.linux-foundation.org > cc: linux-mm at kvack.org > --- > fs/splice.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/fs/splice.c b/fs/splice.c > index 2e76dbb81a8f..8bbd7794d9f0 100644 > --- a/fs/splice.c > +++ b/fs/splice.c > @@ -240,6 +240,8 @@ ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf) > } else if (pipe_full(head, tail, pipe->max_usage)) { > ret = -EAGAIN; > } else { > + if (PageCompound(buf->page)) > + buf->flags &= ~PIPE_BUF_FLAG_GIFT; > pipe->bufs[head & mask] = *buf; > pipe->head = head + 1; > return buf->len; >