diff options
| author | Marco Elver <elver@google.com> | 2019-10-09 17:57:43 +0200 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2019-12-09 21:24:56 +0100 |
| commit | 6cf539a87a61a4fbc43f625267dbcbcf283872ed (patch) | |
| tree | 67da3e86c7156696e3d9da5edd2c1cd76211fec5 /kernel/rcu | |
| parent | rcu: Avoid modifying mask_ofl_ipi in sync_rcu_exp_select_node_cpus() (diff) | |
| download | linux-6cf539a87a61a4fbc43f625267dbcbcf283872ed.tar.xz linux-6cf539a87a61a4fbc43f625267dbcbcf283872ed.zip | |
rcu: Fix data-race due to atomic_t copy-by-value
This fixes a data-race where `atomic_t dynticks` is copied by value. The
copy is performed non-atomically, resulting in a data-race if `dynticks`
is updated concurrently.
This data-race was found with KCSAN:
==================================================================
BUG: KCSAN: data-race in dyntick_save_progress_counter / rcu_irq_enter
write to 0xffff989dbdbe98e0 of 4 bytes by task 10 on cpu 3:
atomic_add_return include/asm-generic/atomic-instrumented.h:78 [inline]
rcu_dynticks_snap kernel/rcu/tree.c:310 [inline]
dyntick_save_progress_counter+0x43/0x1b0 kernel/rcu/tree.c:984
force_qs_rnp+0x183/0x200 kernel/rcu/tree.c:2286
rcu_gp_fqs kernel/rcu/tree.c:1601 [inline]
rcu_gp_fqs_loop+0x71/0x880 kernel/rcu/tree.c:1653
rcu_gp_kthread+0x22c/0x3b0 kernel/rcu/tree.c:1799
kthread+0x1b5/0x200 kernel/kthread.c:255
<snip>
read to 0xffff989dbdbe98e0 of 4 bytes by task 154 on cpu 7:
rcu_nmi_enter_common kernel/rcu/tree.c:828 [inline]
rcu_irq_enter+0xda/0x240 kernel/rcu/tree.c:870
irq_enter+0x5/0x50 kernel/softirq.c:347
<snip>
Reported by Kernel Concurrency Sanitizer on:
CPU: 7 PID: 154 Comm: kworker/7:1H Not tainted 5.3.0+ #5
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
Workqueue: kblockd blk_mq_run_work_fn
==================================================================
Signed-off-by: Marco Elver <elver@google.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 1694a6b57ad8..6145e08a1407 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -577,7 +577,7 @@ static void rcu_eqs_enter(bool user) } lockdep_assert_irqs_disabled(); - trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, rdp->dynticks); + trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, atomic_read(&rdp->dynticks)); WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current)); rdp = this_cpu_ptr(&rcu_data); do_nocb_deferred_wakeup(rdp); @@ -650,14 +650,15 @@ static __always_inline void rcu_nmi_exit_common(bool irq) * leave it in non-RCU-idle state. */ if (rdp->dynticks_nmi_nesting != 1) { - trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2, rdp->dynticks); + trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2, + atomic_read(&rdp->dynticks)); WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */ rdp->dynticks_nmi_nesting - 2); return; } /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */ - trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, rdp->dynticks); + trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, atomic_read(&rdp->dynticks)); WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */ if (irq) @@ -744,7 +745,7 @@ static void rcu_eqs_exit(bool user) rcu_dynticks_task_exit(); rcu_dynticks_eqs_exit(); rcu_cleanup_after_idle(); - trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, rdp->dynticks); + trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, atomic_read(&rdp->dynticks)); WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current)); WRITE_ONCE(rdp->dynticks_nesting, 1); WARN_ON_ONCE(rdp->dynticks_nmi_nesting); @@ -833,7 +834,7 @@ static __always_inline void rcu_nmi_enter_common(bool irq) } trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="), rdp->dynticks_nmi_nesting, - rdp->dynticks_nmi_nesting + incby, rdp->dynticks); + rdp->dynticks_nmi_nesting + incby, atomic_read(&rdp->dynticks)); WRITE_ONCE(rdp->dynticks_nmi_nesting, /* Prevent store tearing. */ rdp->dynticks_nmi_nesting + incby); barrier(); |