From c064a0de1bfb07c34a3798822c7e1636eea866e8 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Sat, 28 Feb 2015 22:24:48 +0100 Subject: [PATCH] livepatch: fix RCU usage in klp_find_external_symbol() 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. [jkosina@suse.cz: change subject line to be aligned with other patches] Cc: Seth Jennings Cc: Josh Poimboeuf Cc: Masami Hiramatsu Cc: Miroslav Benes Cc: Petr Mladek Cc: Jiri Kosina Cc: "Paul E. McKenney" Cc: Rusty Russell Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Masami Hiramatsu Acked-by: Paul E. McKenney Acked-by: Josh Poimboeuf Signed-off-by: Jiri Kosina --- kernel/livepatch/core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index 782172f073c5..01ca08804f51 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -248,11 +248,12 @@ static int klp_find_external_symbol(struct module *pmod, const char *name, /* 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); -- 2.20.1