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[bpf-next,v2,3/4] xsk: avoid store-tearing when assigning umem

Message ID 20190826061053.15996-4-bjorn.topel@gmail.com
State Changes Requested
Delegated to: BPF Maintainers
Headers show
Series xsk: various CPU barrier and {READ, WRITE}_ONCE fixes | expand

Commit Message

Björn Töpel Aug. 26, 2019, 6:10 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.

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

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 8fafa3ce3ae6..e3e99ee5631b 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -716,7 +716,7 @@  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;
 	}