Commit e6762c8b authored Feb 08, 2019 by Magnus Karlsson Committed by Alexei Starovoitov Feb 10, 2019

xsk: add missing smp_rmb() in xsk_mmap

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: 37b07693 ("xsk: add missing write- and data-dependency barrier")
Fixes: c0c77d8f ("xsk: add user memory registration support sockopt")
Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

parent b90efd22

net/xdp/xsk.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -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;

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