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authorQian Cai <cai@lca.pw>2020-02-25 19:27:04 +0300
committerTheodore Ts'o <tytso@mit.edu>2020-02-28 07:21:53 +0300
commite00d996a4317aff5351c4338dd97d390225412c2 (patch)
tree11489ed4f80a83bcc579fcaae90e0542af494597 /drivers/char
parent69efea712f5b0489e67d07565aad5c94e09a3e52 (diff)
downloadlinux-e00d996a4317aff5351c4338dd97d390225412c2.tar.xz
random: fix data races at timer_rand_state
Fields in "struct timer_rand_state" could be accessed concurrently. Lockless plain reads and writes result in data races. Fix them by adding pairs of READ|WRITE_ONCE(). The data races were reported by KCSAN, BUG: KCSAN: data-race in add_timer_randomness / add_timer_randomness write to 0xffff9f320a0a01d0 of 8 bytes by interrupt on cpu 22: add_timer_randomness+0x100/0x190 add_timer_randomness at drivers/char/random.c:1152 add_disk_randomness+0x85/0x280 scsi_end_request+0x43a/0x4a0 scsi_io_completion+0xb7/0x7e0 scsi_finish_command+0x1ed/0x2a0 scsi_softirq_done+0x1c9/0x1d0 blk_done_softirq+0x181/0x1d0 __do_softirq+0xd9/0x57c irq_exit+0xa2/0xc0 do_IRQ+0x8b/0x190 ret_from_intr+0x0/0x42 cpuidle_enter_state+0x15e/0x980 cpuidle_enter+0x69/0xc0 call_cpuidle+0x23/0x40 do_idle+0x248/0x280 cpu_startup_entry+0x1d/0x1f start_secondary+0x1b2/0x230 secondary_startup_64+0xb6/0xc0 no locks held by swapper/22/0. irq event stamp: 32871382 _raw_spin_unlock_irqrestore+0x53/0x60 _raw_spin_lock_irqsave+0x21/0x60 _local_bh_enable+0x21/0x30 irq_exit+0xa2/0xc0 read to 0xffff9f320a0a01d0 of 8 bytes by interrupt on cpu 2: add_timer_randomness+0xe8/0x190 add_disk_randomness+0x85/0x280 scsi_end_request+0x43a/0x4a0 scsi_io_completion+0xb7/0x7e0 scsi_finish_command+0x1ed/0x2a0 scsi_softirq_done+0x1c9/0x1d0 blk_done_softirq+0x181/0x1d0 __do_softirq+0xd9/0x57c irq_exit+0xa2/0xc0 do_IRQ+0x8b/0x190 ret_from_intr+0x0/0x42 cpuidle_enter_state+0x15e/0x980 cpuidle_enter+0x69/0xc0 call_cpuidle+0x23/0x40 do_idle+0x248/0x280 cpu_startup_entry+0x1d/0x1f start_secondary+0x1b2/0x230 secondary_startup_64+0xb6/0xc0 no locks held by swapper/2/0. irq event stamp: 37846304 _raw_spin_unlock_irqrestore+0x53/0x60 _raw_spin_lock_irqsave+0x21/0x60 _local_bh_enable+0x21/0x30 irq_exit+0xa2/0xc0 Reported by Kernel Concurrency Sanitizer on: Hardware name: HP ProLiant BL660c Gen9, BIOS I38 10/17/2018 Link: https://lore.kernel.org/r/1582648024-13111-1-git-send-email-cai@lca.pw Signed-off-by: Qian Cai <cai@lca.pw> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'drivers/char')
-rw-r--r--drivers/char/random.c12
1 files changed, 6 insertions, 6 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c
index c33e7a3cdb13..f43f65c2195d 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1170,14 +1170,14 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
* We take into account the first, second and third-order deltas
* in order to make our estimate.
*/
- delta = sample.jiffies - state->last_time;
- state->last_time = sample.jiffies;
+ delta = sample.jiffies - READ_ONCE(state->last_time);
+ WRITE_ONCE(state->last_time, sample.jiffies);
- delta2 = delta - state->last_delta;
- state->last_delta = delta;
+ delta2 = delta - READ_ONCE(state->last_delta);
+ WRITE_ONCE(state->last_delta, delta);
- delta3 = delta2 - state->last_delta2;
- state->last_delta2 = delta2;
+ delta3 = delta2 - READ_ONCE(state->last_delta2);
+ WRITE_ONCE(state->last_delta2, delta2);
if (delta < 0)
delta = -delta;