Messages in this thread | | | Date | Mon, 2 Mar 2015 15:07:08 -0600 | From | Josh Poimboeuf <> | Subject | Re: [RFC][PATCH 1/9] klp: Fix obvious RCU fail |
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On Sat, Feb 28, 2015 at 10:24:48PM +0100, Peter Zijlstra wrote: > While one must hold RCU-sched (aka. preempt_disable) for find_symbol() > one must equally hold it over the use of the object returned. > > The moment you release the RCU-sched read lock, the object can be dead > and gone. > > Cc: Seth Jennings <sjenning@redhat.com> > Cc: Josh Poimboeuf <jpoimboe@redhat.com> > Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> > Cc: Miroslav Benes <mbenes@suse.cz> > Cc: Petr Mladek <pmladek@suse.cz> > Cc: Jiri Kosina <jkosina@suse.cz> > Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> > Cc: Rusty Russell <rusty@rustcorp.com.au> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
> --- > kernel/livepatch/core.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > --- a/kernel/livepatch/core.c > +++ b/kernel/livepatch/core.c > @@ -248,11 +248,12 @@ static int klp_find_external_symbol(stru > /* first, check if it's an exported symbol */ > preempt_disable(); > sym = find_symbol(name, NULL, NULL, true, true); > - preempt_enable(); > if (sym) { > *addr = sym->value; > + preempt_enable(); > return 0; > } > + preempt_enable(); > > /* otherwise check if it's in another .o within the patch module */ > return klp_find_object_symbol(pmod->name, name, addr); > >
-- Josh
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