This series was original by a bug fix in nvme-over-tcp driver which only
checked whether a page was allocated from slab allcoator, but forgot to
check its page_count: The page handled by sendpage should be neither a
Slab page nor 0 page_count page.
As Sagi Grimberg suggested, the original fix is refind to a more common
inline routine:
static inline bool sendpage_ok(struct page *page)
{
return (!PageSlab(page) && page_count(page) >= 1);
}
If sendpage_ok() returns true, the checking page can be handled by the
zero copy sendpage method in network layer.
The first patch in this series introduces sendpage_ok() in header file
include/linux/net.h, the second patch fixes the page checking issue in
nvme-over-tcp driver, the third patch adds page_count check by using
sendpage_ok() in do_tcp_sendpages() as Eric Dumazet suggested, and all
rested patches just replace existing open coded checks with the inline
sendpage_ok() routine.
Coly Li
Cc: Chaitanya Kulkarni <[email protected]>
Cc: Chris Leech <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Cong Wang <[email protected]>
Cc: David S. Miller <[email protected]>
Cc: Hannes Reinecke <[email protected]>
Cc: Ilya Dryomov <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Jeff Layton <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Lee Duncan <[email protected]>
Cc: Mike Christie <[email protected]>
Cc: Mikhail Skorzhinskii <[email protected]>
Cc: Philipp Reisner <[email protected]>
Cc: Sagi Grimberg <[email protected]>
Cc: [email protected]
Cc: Vasily Averin <[email protected]>
Cc: Vlastimil Babka <[email protected]>
---
Changelog:
v6: fix page check in do_tcp_sendpages(), and replace other open coded
checks with sendpage_ok() in libceph, iscsi drivers.
v5, include linux/mm.h in include/linux/net.h
v4, change sendpage_ok() as an inline helper, and post it as
separate patch.
v3, introduce a more common sendpage_ok()
v2, fix typo in patch subject
v1, the initial version.
Coly Li (6):
net: introduce helper sendpage_ok() in include/linux/net.h
nvme-tcp: check page by sendpage_ok() before calling kernel_sendpage()
tcp: use sendpage_ok() to detect misused .sendpage
drbd: code cleanup by using sendpage_ok() to check page for
kernel_sendpage()
scsi: libiscsi: use sendpage_ok() in iscsi_tcp_segment_map()
libceph: use sendpage_ok() in ceph_tcp_sendpage()
drivers/block/drbd/drbd_main.c | 2 +-
drivers/nvme/host/tcp.c | 7 +++----
drivers/scsi/libiscsi_tcp.c | 2 +-
include/linux/net.h | 16 ++++++++++++++++
net/ceph/messenger.c | 2 +-
net/ipv4/tcp.c | 3 ++-
6 files changed, 24 insertions(+), 8 deletions(-)
--
2.26.2
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 <[email protected]>
Cc: Chaitanya Kulkarni <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Hannes Reinecke <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Mikhail Skorzhinskii <[email protected]>
Cc: Philipp Reisner <[email protected]>
Cc: Sagi Grimberg <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: [email protected]
---
include/linux/net.h | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/include/linux/net.h b/include/linux/net.h
index d48ff1180879..a807fad31958 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,
--
2.26.2
In iscsci driver, iscsi_tcp_segment_map() uses the following code to
check whether the page should or not be handled by sendpage:
if (!recv && page_count(sg_page(sg)) >= 1 && !PageSlab(sg_page(sg)))
The "page_count(sg_page(sg)) >= 1 && !PageSlab(sg_page(sg)" part is to
make sure the page can be sent to network layer's zero copy path. This
part is exactly what sendpage_ok() does.
This patch uses use sendpage_ok() in iscsi_tcp_segment_map() to replace
the original open coded checks.
Signed-off-by: Coly Li <[email protected]>
Cc: Vasily Averin <[email protected]>
Cc: Cong Wang <[email protected]>
Cc: Mike Christie <[email protected]>
Cc: Lee Duncan <[email protected]>
Cc: Chris Leech <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Hannes Reinecke <[email protected]>
---
drivers/scsi/libiscsi_tcp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/scsi/libiscsi_tcp.c b/drivers/scsi/libiscsi_tcp.c
index 6ef93c7af954..31cd8487c16e 100644
--- a/drivers/scsi/libiscsi_tcp.c
+++ b/drivers/scsi/libiscsi_tcp.c
@@ -128,7 +128,7 @@ static void iscsi_tcp_segment_map(struct iscsi_segment *segment, int recv)
* coalescing neighboring slab objects into a single frag which
* triggers one of hardened usercopy checks.
*/
- if (!recv && page_count(sg_page(sg)) >= 1 && !PageSlab(sg_page(sg)))
+ if (!recv && sendpage_ok(sg_page(sg)))
return;
if (recv) {
--
2.26.2
Currently nvme_tcp_try_send_data() doesn't use kernel_sendpage() to
send slab pages. But for pages allocated by __get_free_pages() without
__GFP_COMP, which also have refcount as 0, they are still sent by
kernel_sendpage() to remote end, this is problematic.
The new introduced helper sendpage_ok() checks both PageSlab tag and
page_count counter, and returns true if the checking page is OK to be
sent by kernel_sendpage().
This patch fixes the page checking issue of nvme_tcp_try_send_data()
with sendpage_ok(). If sendpage_ok() returns true, send this page by
kernel_sendpage(), otherwise use sock_no_sendpage to handle this page.
Signed-off-by: Coly Li <[email protected]>
Cc: Chaitanya Kulkarni <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Hannes Reinecke <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Mikhail Skorzhinskii <[email protected]>
Cc: Philipp Reisner <[email protected]>
Cc: Sagi Grimberg <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: [email protected]
---
drivers/nvme/host/tcp.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 62fbaecdc960..902fe742762b 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -912,12 +912,11 @@ static int nvme_tcp_try_send_data(struct nvme_tcp_request *req)
else
flags |= MSG_MORE | MSG_SENDPAGE_NOTLAST;
- /* can't zcopy slab pages */
- if (unlikely(PageSlab(page))) {
- ret = sock_no_sendpage(queue->sock, page, offset, len,
+ if (sendpage_ok(page)) {
+ ret = kernel_sendpage(queue->sock, page, offset, len,
flags);
} else {
- ret = kernel_sendpage(queue->sock, page, offset, len,
+ ret = sock_no_sendpage(queue->sock, page, offset, len,
flags);
}
if (ret <= 0)
--
2.26.2
In _drbd_send_page() a page is checked by following code before sending
it by kernel_sendpage(),
(page_count(page) < 1) || PageSlab(page)
If the check is true, this page won't be send by kernel_sendpage() and
handled by sock_no_sendpage().
This kind of check is exactly what macro sendpage_ok() does, which is
introduced into include/linux/net.h to solve a similar send page issue
in nvme-tcp code.
This patch uses macro sendpage_ok() to replace the open coded checks to
page type and refcount in _drbd_send_page(), as a code cleanup.
Signed-off-by: Coly Li <[email protected]>
Cc: Philipp Reisner <[email protected]>
Cc: Sagi Grimberg <[email protected]>
---
drivers/block/drbd/drbd_main.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index cb687ccdbd96..55dc0c91781e 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -1553,7 +1553,7 @@ static int _drbd_send_page(struct drbd_peer_device *peer_device, struct page *pa
* 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. */
- if (drbd_disable_sendpage || (page_count(page) < 1) || PageSlab(page))
+ if (drbd_disable_sendpage || !sendpage_ok(page))
return _drbd_no_send_page(peer_device, page, offset, size, msg_flags);
msg_flags |= MSG_NOSIGNAL;
--
2.26.2
In libceph, ceph_tcp_sendpage() does the following checks before handle
the page by network layer's zero copy sendpage method,
if (page_count(page) >= 1 && !PageSlab(page))
This check is exactly what sendpage_ok() does. This patch replace the
open coded checks by sendpage_ok() as a code cleanup.
Signed-off-by: Coly Li <[email protected]>
Cc: Ilya Dryomov <[email protected]>
Cc: Jeff Layton <[email protected]>
---
net/ceph/messenger.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 27d6ab11f9ee..6a349da7f013 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -575,7 +575,7 @@ static int ceph_tcp_sendpage(struct socket *sock, struct page *page,
* coalescing neighboring slab objects into a single frag which
* triggers one of hardened usercopy checks.
*/
- if (page_count(page) >= 1 && !PageSlab(page))
+ if (sendpage_ok(page))
sendpage = sock->ops->sendpage;
else
sendpage = sock_no_sendpage;
--
2.26.2
commit a10674bf2406 ("tcp: detecting the misuse of .sendpage for Slab
objects") adds the checks for Slab pages, but the pages don't have
page_count are still missing from the check.
Network layer's sendpage method is not designed to send page_count 0
pages neither, therefore both PageSlab() and page_count() should be
both checked for the sending page. This is exactly what sendpage_ok()
does.
This patch uses sendpage_ok() in do_tcp_sendpages() to detect misused
.sendpage, to make the code more robust.
Fixes: a10674bf2406 ("tcp: detecting the misuse of .sendpage for Slab objects")
Suggested-by: Eric Dumazet <[email protected]>
Signed-off-by: Coly Li <[email protected]>
Cc: Vasily Averin <[email protected]>
Cc: David S. Miller <[email protected]>
Cc: [email protected]
---
net/ipv4/tcp.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 31f3b858db81..d96c7549895a 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -970,7 +970,8 @@ ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
long timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
if (IS_ENABLED(CONFIG_DEBUG_VM) &&
- WARN_ONCE(PageSlab(page), "page must not be a Slab one"))
+ WARN_ONCE(!sendpage_ok(page)),
+ "page must not be a Slab one and have page_count > 0")
return -EINVAL;
/* Wait for a connection to finish. One exception is TCP Fast Open
--
2.26.2