[PATCH] genetlink: Fix uninitialized variable in genl_validate_assign_mc_groups()

[PATCH] genetlink: Fix uninitialized variable in genl_validate_assign_mc_groups()

[Geert Uytterhoeven]

net/netlink/genetlink.c: In function ‘genl_validate_assign_mc_groups’:
net/netlink/genetlink.c:217: warning: ‘err’ may be used uninitialized in this
function

Commit 2a94fe48f32ccf7321450a2cc07f2b724a444e5b ("genetlink: make multicast
groups const, prevent abuse") split genl_register_mc_group() in multiple
functions, but dropped the initialization of err.

Initialize err to zero to fix this.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
Question: Is the for_each_net_rcu() loop in genl_validate_assign_mc_groups()
          guaranteed to loop at least once?
	  If yes, this is a false positive.

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

diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 4518a57aa5fe..803206e82450 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -214,7 +214,7 @@ static int genl_validate_assign_mc_groups(struct genl_family *family)
 {
 	int first_id;
 	int n_groups = family->n_mcgrps;
-	int err, i;
+	int err = 0, i;
 	bool groups_allocated = false;
 
 	if (!n_groups)
-- 
1.7.9.5

Re: [PATCH] genetlink: Fix uninitialized variable in genl_validate_assign_mc_groups()

[David Miller]

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From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Sat, 23 Nov 2013 13:01:50 +0100

> net/netlink/genetlink.c: In function ¡genl_validate_assign_mc_groups¢:
> net/netlink/genetlink.c:217: warning: ¡err¢ may be used uninitialized in this
> function
> 
> Commit 2a94fe48f32ccf7321450a2cc07f2b724a444e5b ("genetlink: make multicast
> groups const, prevent abuse") split genl_register_mc_group() in multiple
> functions, but dropped the initialization of err.
> 
> Initialize err to zero to fix this.
> 
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
> ---
> Question: Is the for_each_net_rcu() loop in genl_validate_assign_mc_groups()
>           guaranteed to loop at least once?
> 	  If yes, this is a false positive.

Applied, but yes it's a false positive.  There is always &init_net so the
loop always iterates at least once.
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