dev->work can re read locklessly in mISDN_read() and mISDN_poll(). Add READ_ONCE()/WRITE_ONCE() annotations. BUG: KCSAN: data-race in mISDN_ioctl / mISDN_read write to 0xffff88812d848280 of 4 bytes by task 10864 on cpu 1: misdn_add_timer drivers/isdn/mISDN/timerdev.c:175 [inline] mISDN_ioctl+0x2fb/0x550 drivers/isdn/mISDN/timerdev.c:233 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xce/0x140 fs/ioctl.c:583 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583 x64_sys_call+0x14b0/0x3000 arch/x86/include/generated/asm/syscalls_64.h:17 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xd8/0x2c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f read to 0xffff88812d848280 of 4 bytes by task 10857 on cpu 0: mISDN_read+0x1f2/0x470 drivers/isdn/mISDN/timerdev.c:112 do_loop_readv_writev fs/read_write.c:847 [inline] vfs_readv+0x3fb/0x690 fs/read_write.c:1020 do_readv+0xe7/0x210 fs/read_write.c:1080 __do_sys_readv fs/read_write.c:1165 [inline] __se_sys_readv fs/read_write.c:1162 [inline] __x64_sys_readv+0x45/0x50 fs/read_write.c:1162 x64_sys_call+0x2831/0x3000 arch/x86/include/generated/asm/syscalls_64.h:20 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xd8/0x2c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f value changed: 0x00000000 -> 0x00000001 Fixes: 1b2b03f8e514 ("Add mISDN core files") Reported-by: syzbot Signed-off-by: Eric Dumazet --- drivers/isdn/mISDN/timerdev.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/drivers/isdn/mISDN/timerdev.c b/drivers/isdn/mISDN/timerdev.c index df98144a953946df0fc8669ae3e446d043b98155..33521c328a827311f0bf02b82e99bfd635ee4ec6 100644 --- a/drivers/isdn/mISDN/timerdev.c +++ b/drivers/isdn/mISDN/timerdev.c @@ -109,14 +109,14 @@ mISDN_read(struct file *filep, char __user *buf, size_t count, loff_t *off) spin_unlock_irq(&dev->lock); if (filep->f_flags & O_NONBLOCK) return -EAGAIN; - wait_event_interruptible(dev->wait, (dev->work || + wait_event_interruptible(dev->wait, (READ_ONCE(dev->work) || !list_empty(list))); if (signal_pending(current)) return -ERESTARTSYS; spin_lock_irq(&dev->lock); } if (dev->work) - dev->work = 0; + WRITE_ONCE(dev->work, 0); if (!list_empty(list)) { timer = list_first_entry(list, struct mISDNtimer, list); list_del(&timer->list); @@ -141,13 +141,16 @@ mISDN_poll(struct file *filep, poll_table *wait) if (*debug & DEBUG_TIMER) printk(KERN_DEBUG "%s(%p, %p)\n", __func__, filep, wait); if (dev) { + u32 work; + poll_wait(filep, &dev->wait, wait); mask = 0; - if (dev->work || !list_empty(&dev->expired)) + work = READ_ONCE(dev->work); + if (work || !list_empty(&dev->expired)) mask |= (EPOLLIN | EPOLLRDNORM); if (*debug & DEBUG_TIMER) printk(KERN_DEBUG "%s work(%d) empty(%d)\n", __func__, - dev->work, list_empty(&dev->expired)); + work, list_empty(&dev->expired)); } return mask; } @@ -172,7 +175,7 @@ misdn_add_timer(struct mISDNtimerdev *dev, int timeout) struct mISDNtimer *timer; if (!timeout) { - dev->work = 1; + WRITE_ONCE(dev->work, 1); wake_up_interruptible(&dev->wait); id = 0; } else { -- 2.52.0.457.g6b5491de43-goog