[PATCH net-next] net: fib_notifier: don't return positive values on fib registration

The function fib6_walk_continue() cannot return a positive value when
called from register_fib_notifier(), but ignoring causes static analyzer to
generate warnings in users of register_fib_notifier() that try to convert
returned error code to pointer with ERR_PTR(). Handle such case by
explicitly checking for positive error values and converting them to
-EINVAL in fib6_tables_dump().

Reported-by: Dan Carpenter <redacted>
Suggested-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Vlad Buslov <redacted>
---
 net/ipv6/ip6_fib.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index f43e27555725..ef9d022e693f 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c

@@ -499,7 +499,7 @@ int fib6_tables_dump(struct net *net, struct notifier_block *nb,
 
 		hlist_for_each_entry_rcu(tb, head, tb6_hlist) {
 			err = fib6_table_dump(net, tb, w);
-			if (err < 0)
+			if (err)
 				goto out;
 		}
 	}

@@ -507,7 +507,8 @@ int fib6_tables_dump(struct net *net, struct notifier_block *nb,
 out:
 	kfree(w);
 
-	return err;
+	/* The tree traversal function should never return a positive value. */
+	return err > 0 ? -EINVAL : err;
 }
 
 static int fib6_dump_node(struct fib6_walker *w)

-- 
2.29.2

Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Thu, 11 Feb 2021 12:07:59 +0200 you wrote:

The function fib6_walk_continue() cannot return a positive value when
called from register_fib_notifier(), but ignoring causes static analyzer to
generate warnings in users of register_fib_notifier() that try to convert
returned error code to pointer with ERR_PTR(). Handle such case by
explicitly checking for positive error values and converting them to
-EINVAL in fib6_tables_dump().

[...]

Here is the summary with links:
  - [net-next] net: fib_notifier: don't return positive values on fib registration
    https://git.kernel.org/netdev/net-next/c/6f1995523a0f

You are awesome, thank you!
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