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Date: Sun, 16 Aug 2020 10:55:09 -0700 From: Cong Wang <xiyou.wangcong@...il.com> To: Coly Li <colyli@...e.de> Cc: linux-block@...r.kernel.org, linux-nvme@...ts.infradead.org, Linux Kernel Network Developers <netdev@...r.kernel.org>, stable <stable@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, Chaitanya Kulkarni <chaitanya.kulkarni@....com>, Christoph Hellwig <hch@....de>, Hannes Reinecke <hare@...e.de>, Jan Kara <jack@...e.com>, Jens Axboe <axboe@...nel.dk>, Mikhail Skorzhinskii <mskorzhinskiy@...arflare.com>, Philipp Reisner <philipp.reisner@...bit.com>, Sagi Grimberg <sagi@...mberg.me>, Vlastimil Babka <vbabka@...e.com> Subject: Re: [PATCH v5 1/3] net: introduce helper sendpage_ok() in include/linux/net.h On Sun, Aug 16, 2020 at 1:36 AM Coly Li <colyli@...e.de> wrote: > > 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. Can we leave this helper to mm subsystem? I know it is for sendpage, but its implementation is all about some mm details and its two callers do not belong to net subsystem either. Think this in another way: who would fix it if it is buggy? I bet mm people should. ;) Thanks.
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