lkml.org 
[lkml]   [2021]   [Jun]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] xfrm: policy: Restructure RCU-read locking in xfrm_sk_policy_lookup
On Fri, Jun 18, 2021 at 04:11:01PM +0200, Varad Gautam wrote:
> Commit "xfrm: policy: Read seqcount outside of rcu-read side in
> xfrm_policy_lookup_bytype" [Linked] resolved a locking bug in
> xfrm_policy_lookup_bytype that causes an RCU reader-writer deadlock on
> the mutex wrapped by xfrm_policy_hash_generation on PREEMPT_RT since
> 77cc278f7b20 ("xfrm: policy: Use sequence counters with associated
> lock").
>
> However, xfrm_sk_policy_lookup can still reach xfrm_policy_lookup_bytype
> while holding rcu_read_lock(), as:
> xfrm_sk_policy_lookup()
> rcu_read_lock()
> security_xfrm_policy_lookup()
> xfrm_policy_lookup()

Hm, I don't see that call chain. security_xfrm_policy_lookup() calls
a hook with the name xfrm_policy_lookup. The only LSM that has
registered a function to that hook is selinux. It registers
selinux_xfrm_policy_lookup() and I don't see how we can call
xfrm_policy_lookup() from there.

Did you actually trigger that bug?

\
 
 \ /
  Last update: 2021-06-21 10:30    [W:0.066 / U:0.308 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site