diff mbox series

[v8,1/7] net: introduce helper sendpage_ok() in include/linux/net.h

Message ID 20200925150119.112016-2-colyli@suse.de
State Superseded
Headers show
Series [v8,1/7] net: introduce helper sendpage_ok() in include/linux/net.h | expand

Commit Message

Coly Li Sept. 25, 2020, 3:01 p.m. UTC
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(+)

Comments

Greg Kroah-Hartman Sept. 25, 2020, 3:18 p.m. UTC | #1
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?

And this feels like a mm thing, why put it in net.h and not mm.h?

thanks,

greg k-h
Greg Kroah-Hartman Sept. 27, 2020, 12:21 p.m. UTC | #2
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
diff mbox series

Patch

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;
+}
+
 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,