net: bridge: remove redundant checks for null p->dev and p->br

Colin Ian King · davem330 · commit 40b1c813ba8e · 2018-11-25T10:25:43.000-08:00
A recent change added a null check on p->dev after p->dev was being dereferenced by the ns_capable check on p->dev. It turns out that neither the p->dev and p->br null checks are necessary, and can be removed, which cleans up a static analyis warning. As Nikolay Aleksandrov noted, these checks can be removed because: "My reasoning of why it shouldn't be possible: - On port add new_nbp() sets both p->dev and p->br before creating kobj/sysfs - On port del (trickier) del_nbp() calls kobject_del() before call_rcu() to destroy the port which in turn calls sysfs_remove_dir() which uses kernfs_remove() which deactivates (shouldn't be able to open new files) and calls kernfs_drain() to drain current open/mmaped files in the respective dir before continuing, thus making it impossible to open a bridge port sysfs file with p->dev and p->br equal to NULL. So I think it's safe to remove those checks altogether. It'd be nice to get a second look over my reasoning as I might be missing something in sysfs/kernfs call path." Thanks to Nikolay Aleksandrov's suggestion to remove the check and David Miller for sanity checking this. Detected by CoverityScan, CID#751490 ("Dereference before null check") Fixes: a5f3ea5 ("net: bridge: add support for raw sysfs port options") Signed-off-by: Colin Ian King <colin.king@canonical.com> Acked-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com> Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/bridge/br_sysfs_if.c b/net/bridge/br_sysfs_if.c
@@ -320,9 +320,6 @@ static ssize_t brport_store(struct kobject *kobj,
 	if (!rtnl_trylock())
 		return restart_syscall();
 
-	if (!p->dev || !p->br)
-		goto out_unlock;
-
 	if (brport_attr->store_raw) {
 		char *buf_copy;
 
