linux-kernel - [tip: locking/kcsan] netfilter: Avoid assigning 'const' pointer to non-const pointer

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Date:   Tue, 12 May 2020 14:36:58 -0000
From:   "tip-bot2 for Will Deacon" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Will Deacon <will@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>,
        "David S. Miller" <davem@...emloft.net>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: locking/kcsan] netfilter: Avoid assigning 'const' pointer to
 non-const pointer

The following commit has been merged into the locking/kcsan branch of tip:

Commit-ID:     f64554152014597a40403ea1a291c80785a2dfe9
Gitweb:        https://git.kernel.org/tip/f64554152014597a40403ea1a291c80785a2dfe9
Author:        Will Deacon <will@...nel.org>
AuthorDate:    Mon, 11 May 2020 21:41:38 +01:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Tue, 12 May 2020 11:04:11 +02:00

netfilter: Avoid assigning 'const' pointer to non-const pointer

nf_remove_net_hook() uses WRITE_ONCE() to assign a 'const' pointer to a
'non-const' pointer. Cleanups to the implementation of WRITE_ONCE() mean
that this will give rise to a compiler warning, just like a plain old
assignment would do:

  | In file included from ./include/linux/export.h:43,
  |                  from ./include/linux/linkage.h:7,
  |                  from ./include/linux/kernel.h:8,
  |                  from net/netfilter/core.c:9:
  | net/netfilter/core.c: In function ‘nf_remove_net_hook’:
  | ./include/linux/compiler.h:216:30: warning: assignment discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
  |   *(volatile typeof(x) *)&(x) = (val);  \
  |                               ^
  | net/netfilter/core.c:379:3: note: in expansion of macro ‘WRITE_ONCE’
  |    WRITE_ONCE(orig_ops[i], &dummy_ops);
  |    ^~~~~~~~~~

Follow the pattern used elsewhere in this file and add a cast to 'void *'
to squash the warning.

Signed-off-by: Will Deacon <will@...nel.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Pablo Neira Ayuso <pablo@...filter.org>
Cc: Jozsef Kadlecsik <kadlec@...filter.org>
Cc: Florian Westphal <fw@...len.de>
Cc: "David S. Miller" <davem@...emloft.net>
Link: https://lkml.kernel.org/r/20200511204150.27858-7-will@kernel.org

---
 net/netfilter/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/core.c b/net/netfilter/core.c
index 78f046e..3ac7c8c 100644
--- a/net/netfilter/core.c
+++ b/net/netfilter/core.c
@@ -376,7 +376,7 @@ static bool nf_remove_net_hook(struct nf_hook_entries *old,
 		if (orig_ops[i] != unreg)
 			continue;
 		WRITE_ONCE(old->hooks[i].hook, accept_all);
-		WRITE_ONCE(orig_ops[i], &dummy_ops);
+		WRITE_ONCE(orig_ops[i], (void *)&dummy_ops);
 		return true;
 	}