lkml.org 
[lkml]   [2015]   [Feb]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] livepatch: RCU protect struct klp_func all the time when used in klp_ftrace_handler()
On Wed, 18 Feb 2015, Petr Mladek wrote:

> func->new_func has been accessed after rcu_read_unlock() in klp_ftrace_handler()
> and therefore the access was not protected.
>
> Signed-off-by: Petr Mladek <pmladek@suse.cz>
> ---
> kernel/livepatch/core.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index ff7f47d026ac..cde66192e20e 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -314,12 +314,12 @@ static void notrace klp_ftrace_handler(unsigned long ip,
> rcu_read_lock();
> func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
> stack_node);
> - rcu_read_unlock();
> -
> if (WARN_ON_ONCE(!func))
> - return;
> + goto unlock;
>
> klp_arch_set_pc(regs, (unsigned long)func->new_func);
> +unlock:
> + rcu_read_unlock();

This can't hurt, even though the only scenario where this could in theory
trigger as a bug (module removal) is non-issue now.

But I'd like to take it nevertheless ... Seth, Josh?

Thanks,

--
Jiri Kosina
SUSE Labs


\
 
 \ /
  Last update: 2015-02-21 00:41    [W:0.044 / U:0.132 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site