KCSAN: data-race in _extract_crng / crng_reseed

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fffe3ae0 Merge tag 'for-linus-hmm' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1127c4fa900000
kernel config: https://syzkaller.appspot.com/x/.config?x=357da2d2fa8fca60
dashboard link: https://syzkaller.appspot.com/bug?extid=616fe97dd2d9cb6f513c
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project.git ca2dcbd030eadbf0aa9b660efe864ff08af6e18b)
CC: [ar...@arndb.de gre...@linuxfoundation.org linux-...@vger.kernel.org ty...@mit.edu]

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+616fe9...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in _extract_crng / crng_reseed

write to 0xffffffff89c455d8 of 8 bytes by task 10306 on cpu 1:
crng_reseed+0x3ed/0x680 drivers/char/random.c:975
_extract_crng+0xcc/0x2d0 drivers/char/random.c:1006
crng_reseed+0x69/0x680 drivers/char/random.c:962
_extract_crng+0xcc/0x2d0 drivers/char/random.c:1006
extract_crng drivers/char/random.c:1026 [inline]
_get_random_bytes+0x141/0x260 drivers/char/random.c:1563
get_random_bytes+0x65/0x110 drivers/char/random.c:1576
eth_random_addr include/linux/etherdevice.h:225 [inline]
nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:507 [inline]
nsim_dev_trap_report drivers/net/netdevsim/dev.c:557 [inline]
nsim_dev_trap_report_work+0x200/0x5c0 drivers/net/netdevsim/dev.c:598
process_one_work+0x3e1/0x9a0 kernel/workqueue.c:2269
worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
kthread+0x20d/0x230 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffffffff89c455d8 of 8 bytes by task 9957 on cpu 0:
_extract_crng+0x47/0x2d0 drivers/char/random.c:1004
crng_reseed+0x69/0x680 drivers/char/random.c:962
_extract_crng+0xcc/0x2d0 drivers/char/random.c:1006
extract_crng drivers/char/random.c:1026 [inline]
_get_random_bytes+0x141/0x260 drivers/char/random.c:1563
get_random_bytes+0x65/0x110 drivers/char/random.c:1576
eth_random_addr include/linux/etherdevice.h:225 [inline]
nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:507 [inline]
nsim_dev_trap_report drivers/net/netdevsim/dev.c:557 [inline]
nsim_dev_trap_report_work+0x200/0x5c0 drivers/net/netdevsim/dev.c:598
process_one_work+0x3e1/0x9a0 kernel/workqueue.c:2269
worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
kthread+0x20d/0x230 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 9957 Comm: kworker/0:4 Not tainted 5.8.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events nsim_dev_trap_report_work
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.