| Message ID | 20200324153643.15527-5-will@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Improve list integrity checking | expand |
On Tue, Mar 24, 2020 at 03:36:26PM +0000, Will Deacon wrote: > timer_pending() open-codes a version of hlist_unhashed() to check > whether or not the 'timer' parameter has been queued in the timer wheel. > KCSAN detects this as a racy operation and explodes at us: > > | BUG: KCSAN: data-race in del_timer / detach_if_pending > | > | write to 0xffff88808697d870 of 8 bytes by task 10 on cpu 0: > | __hlist_del include/linux/list.h:764 [inline] > | detach_timer kernel/time/timer.c:815 [inline] > | detach_if_pending+0xcd/0x2d0 kernel/time/timer.c:832 > | try_to_del_timer_sync+0x60/0xb0 kernel/time/timer.c:1226 > | del_timer_sync+0x6b/0xa0 kernel/time/timer.c:1365 > | schedule_timeout+0x2d2/0x6e0 kernel/time/timer.c:1896 > | rcu_gp_fqs_loop+0x37c/0x580 kernel/rcu/tree.c:1639 > | rcu_gp_kthread+0x143/0x230 kernel/rcu/tree.c:1799 > | kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253 > | ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352 > | > | read to 0xffff88808697d870 of 8 bytes by task 12060 on cpu 1: > | del_timer+0x3b/0xb0 kernel/time/timer.c:1198 > | sk_stop_timer+0x25/0x60 net/core/sock.c:2845 > | inet_csk_clear_xmit_timers+0x69/0xa0 net/ipv4/inet_connection_sock.c:523 > | tcp_clear_xmit_timers include/net/tcp.h:606 [inline] > | tcp_v4_destroy_sock+0xa3/0x3f0 net/ipv4/tcp_ipv4.c:2096 > | inet_csk_destroy_sock+0xf4/0x250 net/ipv4/inet_connection_sock.c:836 > | tcp_close+0x6f3/0x970 net/ipv4/tcp.c:2497 > | inet_release+0x86/0x100 net/ipv4/af_inet.c:427 > | __sock_release+0x85/0x160 net/socket.c:590 > | sock_close+0x24/0x30 net/socket.c:1268 > | __fput+0x1e1/0x520 fs/file_table.c:280 > | ____fput+0x1f/0x30 fs/file_table.c:313 > | task_work_run+0xf6/0x130 kernel/task_work.c:113 > | tracehook_notify_resume include/linux/tracehook.h:188 [inline] > | exit_to_usermode_loop+0x2b4/0x2c0 arch/x86/entry/common.c:163 > > Replace the explicit 'pprev' pointer comparison in timer_pending() with > a call to hlist_unhashed() and initialise the 'expires' timer field > explicitly in do_init_timer() so that the compiler doesn't emit bogus > 'maybe used uninitialised' warnings now that it cannot reason statically > about the result of timer_pending(). > > Cc: Paul E. McKenney <paulmck@kernel.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Eric Dumazet <edumazet@google.com> > Signed-off-by: Will Deacon <will@kernel.org> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/include/linux/timer.h b/include/linux/timer.h index 1e6650ed066d..e9610d2988ba 100644 --- a/include/linux/timer.h +++ b/include/linux/timer.h @@ -158,13 +158,14 @@ static inline void destroy_timer_on_stack(struct timer_list *timer) { } * * timer_pending will tell whether a given timer is currently pending, * or not. Callers must ensure serialization wrt. other operations done - * to this timer, eg. interrupt contexts, or other CPUs on SMP. + * to this timer, eg. interrupt contexts, or other CPUs on SMP if they + * cannot tolerate spurious results. * * return value: 1 if the timer is pending, 0 if not. */ static inline int timer_pending(const struct timer_list * timer) { - return timer->entry.pprev != NULL; + return !hlist_unhashed(&timer->entry); } extern void add_timer_on(struct timer_list *timer, int cpu); diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 4820823515e9..9e1c6fc8433a 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -780,6 +780,7 @@ static void do_init_timer(struct timer_list *timer, const char *name, struct lock_class_key *key) { timer->entry.pprev = NULL; + timer->expires = 0; /* Avoid bogus 'maybe used uninitialized' warning */ timer->function = func; timer->flags = flags | raw_smp_processor_id(); lockdep_init_map(&timer->lockdep_map, name, key, 0);
timer_pending() open-codes a version of hlist_unhashed() to check whether or not the 'timer' parameter has been queued in the timer wheel. KCSAN detects this as a racy operation and explodes at us: | BUG: KCSAN: data-race in del_timer / detach_if_pending | | write to 0xffff88808697d870 of 8 bytes by task 10 on cpu 0: | __hlist_del include/linux/list.h:764 [inline] | detach_timer kernel/time/timer.c:815 [inline] | detach_if_pending+0xcd/0x2d0 kernel/time/timer.c:832 | try_to_del_timer_sync+0x60/0xb0 kernel/time/timer.c:1226 | del_timer_sync+0x6b/0xa0 kernel/time/timer.c:1365 | schedule_timeout+0x2d2/0x6e0 kernel/time/timer.c:1896 | rcu_gp_fqs_loop+0x37c/0x580 kernel/rcu/tree.c:1639 | rcu_gp_kthread+0x143/0x230 kernel/rcu/tree.c:1799 | kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253 | ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352 | | read to 0xffff88808697d870 of 8 bytes by task 12060 on cpu 1: | del_timer+0x3b/0xb0 kernel/time/timer.c:1198 | sk_stop_timer+0x25/0x60 net/core/sock.c:2845 | inet_csk_clear_xmit_timers+0x69/0xa0 net/ipv4/inet_connection_sock.c:523 | tcp_clear_xmit_timers include/net/tcp.h:606 [inline] | tcp_v4_destroy_sock+0xa3/0x3f0 net/ipv4/tcp_ipv4.c:2096 | inet_csk_destroy_sock+0xf4/0x250 net/ipv4/inet_connection_sock.c:836 | tcp_close+0x6f3/0x970 net/ipv4/tcp.c:2497 | inet_release+0x86/0x100 net/ipv4/af_inet.c:427 | __sock_release+0x85/0x160 net/socket.c:590 | sock_close+0x24/0x30 net/socket.c:1268 | __fput+0x1e1/0x520 fs/file_table.c:280 | ____fput+0x1f/0x30 fs/file_table.c:313 | task_work_run+0xf6/0x130 kernel/task_work.c:113 | tracehook_notify_resume include/linux/tracehook.h:188 [inline] | exit_to_usermode_loop+0x2b4/0x2c0 arch/x86/entry/common.c:163 Replace the explicit 'pprev' pointer comparison in timer_pending() with a call to hlist_unhashed() and initialise the 'expires' timer field explicitly in do_init_timer() so that the compiler doesn't emit bogus 'maybe used uninitialised' warnings now that it cannot reason statically about the result of timer_pending(). Cc: Paul E. McKenney <paulmck@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Eric Dumazet <edumazet@google.com> Signed-off-by: Will Deacon <will@kernel.org> --- include/linux/timer.h | 5 +++-- kernel/time/timer.c | 1 + 2 files changed, 4 insertions(+), 2 deletions(-)