Commit c381b079 authored Oct 02, 2020 by Coly Li Committed by David S. Miller Oct 02, 2020

net: introduce helper sendpage_ok() in include/linux/net.h



The original problem was from nvme-over-tcp code, who mistakenly uses
kernel_sendpage() to send pages allocated by __get_free_pages() without
__GFP_COMP flag. Such pages don't have refcount (page_count is 0) on
tail pages, sending them by kernel_sendpage() may trigger a kernel panic
from a corrupted kernel heap, because these pages are incorrectly freed
in network stack as page_count 0 pages.

This patch introduces a helper sendpage_ok(), it returns true if the
checking page,
- is not slab page: PageSlab(page) is false.
- has page refcount: page_count(page) is not zero

All drivers who want to send page to remote end by kernel_sendpage()
may use this helper to check whether the page is OK. If the helper does
not return true, the driver should try other non sendpage method (e.g.
sock_no_sendpage()) to handle the page.

Signed-off-by: Coly Li <colyli@suse.de>
Cc: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Jan Kara <jack@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Mikhail Skorzhinskii <mskorzhinskiy@solarflare.com>
Cc: Philipp Reisner <philipp.reisner@linbit.com>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Vlastimil Babka <vbabka@suse.com>
Cc: stable@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>

parent f30e25a9

include/linux/net.h

+16 −0

Original line number	Diff line number	Diff line
		@@ -21,6 +21,7 @@
		#include <linux/rcupdate.h>
		#include <linux/once.h>
		#include <linux/fs.h>
		#include <linux/mm.h>
		#include <linux/sockptr.h>

		#include <uapi/linux/net.h>
		@@ -286,6 +287,21 @@ do { \
		#define net_get_random_once_wait(buf, nbytes) \
		get_random_once_wait((buf), (nbytes))

		/*
		* E.g. XFS meta- & log-data is in slab pages, or bcache meta
		* data pages, or other high order pages allocated by
		* __get_free_pages() without __GFP_COMP, which have a page_count
		* of 0 and/or have PageSlab() set. We cannot use send_page for
		* those, as that does get_page(); put_page(); and would cause
		* either a VM_BUG directly, or __page_cache_release a page that
		* would actually still be referenced by someone, leading to some
		* obscure delayed Oops somewhere else.
		*/
		static inline bool sendpage_ok(struct page *page)
		{
		return !PageSlab(page) && page_count(page) >= 1;
		}

		int kernel_sendmsg(struct socket sock, struct msghdr msg, struct kvec *vec,
		size_t num, size_t len);
		int kernel_sendmsg_locked(struct sock sk, struct msghdr msg,

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