diff options
| author | Marco Elver <elver@google.com> | 2020-01-15 17:25:12 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2020-03-21 09:41:16 +0100 |
| commit | f1bc96210c6a6b853b4b2eec808141956e8fbc5d (patch) | |
| tree | 00cd5ab43c89dcbde1bec5c5e3dcbb56b74a1647 /kernel/kcsan | |
| parent | 05f9a4067964e3f864210271a6299f13d2eeea55 (diff) | |
kcsan: Make KCSAN compatible with lockdep
We must avoid any recursion into lockdep if KCSAN is enabled on utilities
used by lockdep. One manifestation of this is corruption of lockdep's
IRQ trace state (if TRACE_IRQFLAGS), resulting in spurious warnings
(see below). This commit fixes this by:
1. Using raw_local_irq{save,restore} in kcsan_setup_watchpoint().
2. Disabling lockdep in kcsan_report().
Tested with:
CONFIG_LOCKDEP=y
CONFIG_DEBUG_LOCKDEP=y
CONFIG_TRACE_IRQFLAGS=y
This fix eliminates spurious warnings such as the following one:
WARNING: CPU: 0 PID: 2 at kernel/locking/lockdep.c:4406 check_flags.part.0+0x101/0x220
Modules linked in:
CPU: 0 PID: 2 Comm: kthreadd Not tainted 5.5.0-rc1+ #11
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
RIP: 0010:check_flags.part.0+0x101/0x220
<snip>
Call Trace:
lock_is_held_type+0x69/0x150
freezer_fork+0x20b/0x370
cgroup_post_fork+0x2c9/0x5c0
copy_process+0x2675/0x3b40
_do_fork+0xbe/0xa30
? _raw_spin_unlock_irqrestore+0x40/0x50
? match_held_lock+0x56/0x250
? kthread_park+0xf0/0xf0
kernel_thread+0xa6/0xd0
? kthread_park+0xf0/0xf0
kthreadd+0x321/0x3d0
? kthread_create_on_cpu+0x130/0x130
ret_from_fork+0x3a/0x50
irq event stamp: 64
hardirqs last enabled at (63): [<ffffffff9a7995d0>] _raw_spin_unlock_irqrestore+0x40/0x50
hardirqs last disabled at (64): [<ffffffff992a96d2>] kcsan_setup_watchpoint+0x92/0x460
softirqs last enabled at (32): [<ffffffff990489b8>] fpu__copy+0xe8/0x470
softirqs last disabled at (30): [<ffffffff99048939>] fpu__copy+0x69/0x470
Reported-by: Qian Cai <cai@lca.pw>
Signed-off-by: Marco Elver <elver@google.com>
Acked-by: Alexander Potapenko <glider@google.com>
Tested-by: Qian Cai <cai@lca.pw>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/kcsan')
| -rw-r--r-- | kernel/kcsan/core.c | 6 | ||||
| -rw-r--r-- | kernel/kcsan/report.c | 11 |
2 files changed, 15 insertions, 2 deletions
diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c index 87bf857c8893..64b30f7716a1 100644 --- a/kernel/kcsan/core.c +++ b/kernel/kcsan/core.c @@ -336,8 +336,10 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) * CPU-local data accesses), it makes more sense (from a data race * detection point of view) to simply disable preemptions to ensure * as many tasks as possible run on other CPUs. + * + * Use raw versions, to avoid lockdep recursion via IRQ flags tracing. */ - local_irq_save(irq_flags); + raw_local_irq_save(irq_flags); watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write); if (watchpoint == NULL) { @@ -429,7 +431,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS); out_unlock: - local_irq_restore(irq_flags); + raw_local_irq_restore(irq_flags); out: user_access_restore(ua_flags); } diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c index b5b4feea49de..33bdf8b229b5 100644 --- a/kernel/kcsan/report.c +++ b/kernel/kcsan/report.c @@ -2,6 +2,7 @@ #include <linux/jiffies.h> #include <linux/kernel.h> +#include <linux/lockdep.h> #include <linux/preempt.h> #include <linux/printk.h> #include <linux/sched.h> @@ -410,6 +411,14 @@ void kcsan_report(const volatile void *ptr, size_t size, int access_type, { unsigned long flags = 0; + /* + * With TRACE_IRQFLAGS, lockdep's IRQ trace state becomes corrupted if + * we do not turn off lockdep here; this could happen due to recursion + * into lockdep via KCSAN if we detect a data race in utilities used by + * lockdep. + */ + lockdep_off(); + kcsan_disable_current(); if (prepare_report(&flags, ptr, size, access_type, cpu_id, type)) { if (print_report(ptr, size, access_type, value_change, cpu_id, type) && panic_on_warn) @@ -418,4 +427,6 @@ void kcsan_report(const volatile void *ptr, size_t size, int access_type, release_report(&flags, type); } kcsan_enable_current(); + + lockdep_on(); } |