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From: Magnus Karlsson <magnus.karlsson@intel.com>
To: magnus.karlsson@intel.com, bjorn.topel@intel.com, ast@kernel.org,
	daniel@iogearbox.net, netdev@vger.kernel.org
Subject: [PATCH bpf] xsk: add missing smp_rmb() in xsk_mmap
Date: Fri,  8 Feb 2019 14:13:50 +0100	[thread overview]
Message-ID: <1549631630-29208-1-git-send-email-magnus.karlsson@intel.com> (raw)

All the setup code in AF_XDP is protected by a mutex with the
exception of the mmap code that cannot use it. To make sure that a
process banging on the mmap call at the same time as another process
is setting up the socket, smp_wmb() calls were added in the umem
registration code and the queue creation code, so that the published
structures that xsk_mmap needs would be consistent. However, the
corresponding smp_rmb() calls were not added to the xsk_mmap
code. This patch adds these calls.

Fixes: 37b076933a8e3 ("xsk: add missing write- and data-dependency barrier")
Fixes: c0c77d8fb787c ("xsk: add user memory registration support sockopt")
Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
---
 net/xdp/xsk.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index a032684..45f3b52 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -669,6 +669,8 @@ static int xsk_mmap(struct file *file, struct socket *sock,
 		if (!umem)
 			return -EINVAL;
 
+		/* Matches the smp_wmb() in XDP_UMEM_REG */
+		smp_rmb();
 		if (offset == XDP_UMEM_PGOFF_FILL_RING)
 			q = READ_ONCE(umem->fq);
 		else if (offset == XDP_UMEM_PGOFF_COMPLETION_RING)
@@ -678,6 +680,8 @@ static int xsk_mmap(struct file *file, struct socket *sock,
 	if (!q)
 		return -EINVAL;
 
+	/* Matches the smp_wmb() in xsk_init_queue */
+	smp_rmb();
 	qpg = virt_to_head_page(q->ring);
 	if (size > (PAGE_SIZE << compound_order(qpg)))
 		return -EINVAL;
-- 
2.7.4


             reply	other threads:[~2019-02-08 13:14 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-08 13:13 Magnus Karlsson [this message]
2019-02-11  4:08 ` [PATCH bpf] xsk: add missing smp_rmb() in xsk_mmap Alexei Starovoitov

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