[PATCH] net/dns_resolver: dns_query Modify parameter checking to avoid dead code

From: nixiaoming
Date: Mon Jun 04 2018 - 03:05:33 EST


After commit 1a4240f4764a ("DNS: Separate out CIFS DNS Resolver code")
a dead code exists in function dns_query

code show as below:
if (!name || namelen == 0)
return -EINVAL;
/*Now the value of "namelen" cannot be equal to 0*/
....
if (!namelen) /*The condition "!namelen"" cannot be true*/
namelen = strnlen(name, 256); /*deadcode*/

Modify parameter checking to avoid dead code

Signed-off-by: nixiaoming <nixiaoming@xxxxxxxxxx>
---
net/dns_resolver/dns_query.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/net/dns_resolver/dns_query.c b/net/dns_resolver/dns_query.c
index 49da670..f2acee2 100644
--- a/net/dns_resolver/dns_query.c
+++ b/net/dns_resolver/dns_query.c
@@ -81,7 +81,9 @@ int dns_query(const char *type, const char *name, size_t namelen,
kenter("%s,%*.*s,%zu,%s",
type, (int)namelen, (int)namelen, name, namelen, options);

- if (!name || namelen == 0)
+ if (!name || namelen < 3 || namelen > 255)
+ return -EINVAL;
+ if (namelen > strnlen(name, 256)) /*maybe only need part of name*/
return -EINVAL;

/* construct the query key description as "[<type>:]<name>" */
@@ -94,10 +96,6 @@ int dns_query(const char *type, const char *name, size_t namelen,
desclen += typelen + 1;
}

- if (!namelen)
- namelen = strnlen(name, 256);
- if (namelen < 3 || namelen > 255)
- return -EINVAL;
desclen += namelen + 1;

desc = kmalloc(desclen, GFP_KERNEL);
--
2.10.1