lkml.org 
[lkml]   [2018]   [Nov]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH][V2] net: bridge: remove redundant checks for null p->dev and p->br
Date
From: Colin Ian King <colin.king@canonical.com>

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: a5f3ea54f3cc ("net: bridge: add support for raw sysfs port options")
Signed-off-by: Colin Ian King <colin.king@canonical.com>

---

V2: remove checks instead of moving them before the dereference of
p->dev.
---
net/bridge/br_sysfs_if.c | 3 ---
1 file changed, 3 deletions(-)

diff --git a/net/bridge/br_sysfs_if.c b/net/bridge/br_sysfs_if.c
index 7c87a2fe5248..88715edb119a 100644
--- 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;

--
2.19.1
\
 
 \ /
  Last update: 2018-11-25 17:11    [W:0.028 / U:0.508 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site