From: Greg KH <gregkh@linuxfoundation.org>
To: Coly Li <colyli@suse.de>
Cc: linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
netdev@vger.kernel.org, open-iscsi@googlegroups.com,
linux-scsi@vger.kernel.org, ceph-devel@vger.kernel.org,
linux-kernel@vger.kernel.org,
Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>,
Christoph Hellwig <hch@lst.de>, Hannes Reinecke <hare@suse.de>,
Jan Kara <jack@suse.com>, Jens Axboe <axboe@kernel.dk>,
Mikhail Skorzhinskii <mskorzhinskiy@solarflare.com>,
Philipp Reisner <philipp.reisner@linbit.com>,
Sagi Grimberg <sagi@grimberg.me>,
Vlastimil Babka <vbabka@suse.com>,
stable@vger.kernel.org
Subject: Re: [PATCH v8 1/7] net: introduce helper sendpage_ok() in include/linux/net.h
Date: Sun, 27 Sep 2020 14:21:15 +0200 [thread overview]
Message-ID: <20200927122115.GA178781@kroah.com> (raw)
In-Reply-To: <7b0d4f63-2fe5-9032-3b88-97619d8c5081@suse.de>
On Sat, Sep 26, 2020 at 09:28:03PM +0800, Coly Li wrote:
> On 2020/9/25 23:18, Greg KH wrote:
> > On Fri, Sep 25, 2020 at 11:01:13PM +0800, Coly Li 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.
> >>
> >> 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
> >> ---
> >> include/linux/net.h | 16 ++++++++++++++++
> >> 1 file changed, 16 insertions(+)
> >>
> >> diff --git a/include/linux/net.h b/include/linux/net.h
> >> index d48ff1180879..05db8690f67e 100644
> >> --- a/include/linux/net.h
> >> +++ b/include/linux/net.h
> >> @@ -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;
> >
> > Do you have one extra ' ' after "return" there?
>
> It should be fixed in next version.
>
> >
> > And this feels like a mm thing, why put it in net.h and not mm.h?
>
> This check is specific for kernel_sendpage(), so I want to place it
> closer to where kernel_sendpage() is declared.
>
> And indeed there was similar discussion about why this helper is not in
> mm code in v5 series. Christoph supported to place sendpage_ok() in
> net.h, an uncompleted piece of his opinion was "It is not a mm bug, it
> is a networking quirk."
Ah, nevermind then, sorry for the noise :)
greg k-h
next prev parent reply other threads:[~2020-09-27 12:21 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-25 15:01 [PATCH v8 0/7] Introduce sendpage_ok() to detect misused sendpage in network related drivers Coly Li
2020-09-25 15:01 ` [PATCH v8 1/7] net: introduce helper sendpage_ok() in include/linux/net.h Coly Li
2020-09-25 15:18 ` Greg KH
2020-09-26 13:28 ` Coly Li
2020-09-27 12:21 ` Greg KH [this message]
2020-09-25 15:01 ` [PATCH v8 2/7] net: add WARN_ONCE in kernel_sendpage() for improper zero-copy send Coly Li
2020-09-25 15:01 ` [PATCH v8 3/7] nvme-tcp: check page by sendpage_ok() before calling kernel_sendpage() Coly Li
2020-09-25 15:01 ` [PATCH v8 4/7] tcp: use sendpage_ok() to detect misused .sendpage Coly Li
2020-09-25 15:01 ` [PATCH v8 5/7] drbd: code cleanup by using sendpage_ok() to check page for kernel_sendpage() Coly Li
2020-09-25 15:01 ` [PATCH v8 6/7] scsi: libiscsi: use sendpage_ok() in iscsi_tcp_segment_map() Coly Li
2020-09-25 20:54 ` Martin K. Petersen
2020-09-25 15:01 ` [PATCH v8 7/7] libceph: use sendpage_ok() in ceph_tcp_sendpage() Coly Li
2020-09-25 15:13 ` Jeff Layton
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