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Subject[PATCH 1/2] net/wireless/nl80211.c: Avoid call to genlmsg_cancel
Date
genlmsg_cancel subtracts some constants from its second argument before
calling nlmsg_cancel. nlmsg_cancel then calls nlmsg_trim on the same
arguments. nlmsg_trim tests for NULL before doing any computation, but a
NULL second argument to genlmsg_cancel is no longer NULL due to the initial
subtraction. Nothing else happens in this execution, so the call to
genlmsg_cancel is simply unnecessary in this case.

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression data;
@@

if (data == NULL) { ...
* genlmsg_cancel(..., data);
...
return ...;
}
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>

---
net/wireless/nl80211.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 9b62710..864ddfb 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -2718,7 +2718,7 @@ static int nl80211_get_mesh_config(struct sk_buff *skb,
hdr = nl80211hdr_put(msg, info->snd_pid, info->snd_seq, 0,
NL80211_CMD_GET_MESH_CONFIG);
if (!hdr)
- goto nla_put_failure;
+ goto out;
pinfoattr = nla_nest_start(msg, NL80211_ATTR_MESH_CONFIG);
if (!pinfoattr)
goto nla_put_failure;
@@ -2759,6 +2759,7 @@ static int nl80211_get_mesh_config(struct sk_buff *skb,

nla_put_failure:
genlmsg_cancel(msg, hdr);
+ out:
nlmsg_free(msg);
return -ENOBUFS;
}
@@ -2954,7 +2955,7 @@ static int nl80211_get_reg(struct sk_buff *skb, struct genl_info *info)
hdr = nl80211hdr_put(msg, info->snd_pid, info->snd_seq, 0,
NL80211_CMD_GET_REG);
if (!hdr)
- goto nla_put_failure;
+ goto put_failure;

NLA_PUT_STRING(msg, NL80211_ATTR_REG_ALPHA2,
cfg80211_regdomain->alpha2);
@@ -3001,6 +3002,7 @@ static int nl80211_get_reg(struct sk_buff *skb, struct genl_info *info)

nla_put_failure:
genlmsg_cancel(msg, hdr);
+put_failure:
nlmsg_free(msg);
err = -EMSGSIZE;
out:


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