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[PATCH] genetlink: fix unsigned int comparison with less than zero

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  [PATCH] genetlink: fix unsigned int comparison with less than zero Colin King <colin.king@canonical.com> - 2016-11-10 17:00 +0100
    Re: [PATCH] genetlink: fix unsigned int comparison with less than zero Cong Wang <xiyou.wangcong@gmail.com> - 2016-11-10 18:20 +0100

#1519080 — [PATCH] genetlink: fix unsigned int comparison with less than zero

From: Colin Ian King <colin.king@canonical.com>

family->id is unsigned, so the less than zero check for
failure return from idr_alloc is never true and so the error exit
is never handled.  Instead, assign err and check if this is less
than zero since this is a signed integer.

Issue found with static analysis with CoverityScan, CID 1375916

Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 net/netlink/genetlink.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index f0b65fe..2ea61ba 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -360,12 +360,10 @@ int genl_register_family(struct genl_family *family)
 	} else
 		family->attrbuf = NULL;
 
-	family->id = idr_alloc(&genl_fam_idr, family,
+	family->id = err = idr_alloc(&genl_fam_idr, family,
 			       start, end + 1, GFP_KERNEL);
-	if (family->id < 0) {
-		err = family->id;
+	if (err < 0)
 		goto errout_free;
-	}
 
 	err = genl_validate_assign_mc_groups(family);
 	if (err)
-- 
2.10.2

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#1519160

On Thu, Nov 10, 2016 at 7:57 AM, Colin King <colin.king@canonical.com> wrote:
> From: Colin Ian King <colin.king@canonical.com>
>
> family->id is unsigned, so the less than zero check for
> failure return from idr_alloc is never true and so the error exit
> is never handled.  Instead, assign err and check if this is less
> than zero since this is a signed integer.

Why family->id can't be just signed int? For me it should be.

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