[bpf-next,3/4] xsk: avoid store-tearing when assigning umem
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Message ID 20190822091306.20581-4-bjorn.topel@gmail.com
State Changes Requested
Delegated to: BPF Maintainers
Headers show
Series
  • xsk: various CPU barrier and {READ, WRITE}_ONCE fixes
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Commit Message

Björn Töpel Aug. 22, 2019, 9:13 a.m. UTC
From: Björn Töpel <bjorn.topel@intel.com>

The umem member of struct xdp_sock is read outside of the control
mutex, in the mmap implementation, and needs a WRITE_ONCE to avoid
potentional store-tearing.

Fixes: 423f38329d26 ("xsk: add umem fill queue support and mmap")
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
---
 net/xdp/xsk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Jonathan Lemon Aug. 23, 2019, 4:44 p.m. UTC | #1
On 22 Aug 2019, at 2:13, Björn Töpel wrote:

> From: Björn Töpel <bjorn.topel@intel.com>
>
> The umem member of struct xdp_sock is read outside of the control
> mutex, in the mmap implementation, and needs a WRITE_ONCE to avoid
> potentional store-tearing.
>
> Fixes: 423f38329d26 ("xsk: add umem fill queue support and mmap")
> Signed-off-by: Björn Töpel <bjorn.topel@intel.com>

Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com>

Patch
diff mbox series

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 31236e61069b..6dde1857ed52 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -718,7 +718,7 @@  static int xsk_setsockopt(struct socket *sock, int level, int optname,
 
 		/* Make sure umem is ready before it can be seen by others */
 		smp_wmb();
-		xs->umem = umem;
+		WRITE_ONCE(xs->umem, umem);
 		mutex_unlock(&xs->mutex);
 		return 0;
 	}