From 73d20564e0dcae003e0d79977f044d5e57496304 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Tue, 31 Mar 2020 22:18:49 +0200 Subject: [PATCH] hrtimer: Don't dereference the hrtimer pointer after the callback A hrtimer can be released in its callback, but lockdep_hrtimer_exit() dereferences the pointer after the callback returns, i.e. a potential use after free. Retrieve the context in which the hrtimer expires before the callback is invoked and use it in lockdep_hrtimer_exit(). Fixes: 40db173965c0 ("lockdep: Add hrtimer context tracing bits") Reported-by: syzbot+62c155c276e580cfb606@syzkaller.appspotmail.com Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20200331201849.fkp2siy3vcdqvqlz@linutronix.de --- include/linux/irqflags.h | 27 ++++++++++++++++----------- kernel/time/hrtimer.c | 5 +++-- 2 files changed, 19 insertions(+), 13 deletions(-) diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h index ceca42de4438..61a9ced3aa50 100644 --- a/include/linux/irqflags.h +++ b/include/linux/irqflags.h @@ -58,16 +58,21 @@ do { \ } while (0) # define lockdep_hrtimer_enter(__hrtimer) \ - do { \ - if (!__hrtimer->is_hard) \ - current->irq_config = 1; \ - } while (0) - -# define lockdep_hrtimer_exit(__hrtimer) \ - do { \ - if (!__hrtimer->is_hard) \ +({ \ + bool __expires_hardirq = true; \ + \ + if (!__hrtimer->is_hard) { \ + current->irq_config = 1; \ + __expires_hardirq = false; \ + } \ + __expires_hardirq; \ +}) + +# define lockdep_hrtimer_exit(__expires_hardirq) \ + do { \ + if (!__expires_hardirq) \ current->irq_config = 0; \ - } while (0) + } while (0) # define lockdep_posixtimer_enter() \ do { \ @@ -102,8 +107,8 @@ do { \ # define lockdep_hardirq_exit() do { } while (0) # define lockdep_softirq_enter() do { } while (0) # define lockdep_softirq_exit() do { } while (0) -# define lockdep_hrtimer_enter(__hrtimer) do { } while (0) -# define lockdep_hrtimer_exit(__hrtimer) do { } while (0) +# define lockdep_hrtimer_enter(__hrtimer) false +# define lockdep_hrtimer_exit(__context) do { } while (0) # define lockdep_posixtimer_enter() do { } while (0) # define lockdep_posixtimer_exit() do { } while (0) # define lockdep_irq_work_enter(__work) do { } while (0) diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index d0a5ba37aff4..d89da1c7e005 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -1480,6 +1480,7 @@ static void __run_hrtimer(struct hrtimer_cpu_base *cpu_base, unsigned long flags) __must_hold(&cpu_base->lock) { enum hrtimer_restart (*fn)(struct hrtimer *); + bool expires_in_hardirq; int restart; lockdep_assert_held(&cpu_base->lock); @@ -1514,11 +1515,11 @@ static void __run_hrtimer(struct hrtimer_cpu_base *cpu_base, */ raw_spin_unlock_irqrestore(&cpu_base->lock, flags); trace_hrtimer_expire_entry(timer, now); - lockdep_hrtimer_enter(timer); + expires_in_hardirq = lockdep_hrtimer_enter(timer); restart = fn(timer); - lockdep_hrtimer_exit(timer); + lockdep_hrtimer_exit(expires_in_hardirq); trace_hrtimer_expire_exit(timer); raw_spin_lock_irq(&cpu_base->lock); -- 2.30.2