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ip: silence udp zerocopy smatch false positive

PATCH Applied Willem de Bruijn 2 participants 2 messages Dec 8, 2018

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Networking Network drivers IPv4/IPv6
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Willem de Bruijn

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#0 lore raw

PATCH 1/1 ip: silence udp zerocopy smatch false positive

From: Willem de Bruijn <[email protected]>

extra_uref is used in __ip(6)_append_data only if uarg is set.

Smatch sees that the variable is passed to sock_zerocopy_put_abort. This function accesses it only when uarg is set, but smatch cannot infer this.

Make this dependency explicit.

Fixes 52900d22288e ("udp: elide zerocopy operation in hot path")
Signed-off-by Willem de Bruijn <[email protected]>
---
 net/ipv4/ip_output.c  | 3 ++-
 net/ipv6/ip6_output.c | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)
net/ipv4/ip_output.c +2 -1
index 78f028bdad30b..ab6618036afed 100644
@@ -1130,7 +1130,8 @@ static int __ip_append_data(struct sock *sk,
 error_efault:
 	err = -EFAULT;
 error:
-	sock_zerocopy_put_abort(uarg, extra_uref);
+	if (uarg)
+		sock_zerocopy_put_abort(uarg, extra_uref);
 	cork->length -= length;
 	IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
 	refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc);
net/ipv6/ip6_output.c +2 -1
index 6592a39e5ec10..be25b34dc5c2f 100644
@@ -1575,7 +1575,8 @@ static int __ip6_append_data(struct sock *sk,
 error_efault:
 	err = -EFAULT;
 error:
-	sock_zerocopy_put_abort(uarg, extra_uref);
+	if (uarg)
+		sock_zerocopy_put_abort(uarg, extra_uref);
 	cork->length -= length;
 	IP6_INC_STATS(sock_net(sk), rt->rt6i_idev, IPSTATS_MIB_OUTDISCARDS);
 	refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc);
Signature · 1 line
2.20.0.rc2.403.gdbc3b29805-goog
maintainer Applied
#1 lore raw

From: Willem de Bruijn <[email protected]>
Date: Sat, 8 Dec 2018 06:22:46 -0500

Quoted 4 lines

From: Willem de Bruijn <[email protected]>

extra_uref is used in __ip(6)_append_data only if uarg is set.

Quoted 8 lines

Smatch sees that the variable is passed to sock_zerocopy_put_abort. This function accesses it only when uarg is set, but smatch cannot infer this.

Make this dependency explicit.

Fixes 52900d22288e ("udp: elide zerocopy operation in hot path")
Signed-off-by Willem de Bruijn <[email protected]>

I looked and can't figure out a better way to fix this :)

Applied, thanks Willem.