+RCU folks On Mon, 4 Nov 2019 at 12:30, syzbot <syzbot+99f4ddade3c22ab0cf23@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > Hello, > > syzbot found the following crash on: > > HEAD commit: 05f22368 x86, kcsan: Enable KCSAN for x86 > git tree: https://github.com/google/ktsan.git kcsan > console output: https://syzkaller.appspot.com/x/log.txt?x=1296ff50e00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=87d111955f40591f > dashboard link: https://syzkaller.appspot.com/bug?extid=99f4ddade3c22ab0cf23 > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > Unfortunately, I don't have any reproducer for this crash yet. > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+99f4ddade3c22ab0cf23@xxxxxxxxxxxxxxxxxxxxxxxxx > > ================================================================== > BUG: KCSAN: data-race in __rcu_read_unlock / sync_rcu_exp_select_cpus > > read to 0xffffffff85a7d440 of 8 bytes by task 7624 on cpu 0: > rcu_read_unlock_special kernel/rcu/tree_plugin.h:615 [inline] > __rcu_read_unlock+0x381/0x3c0 kernel/rcu/tree_plugin.h:383 > rcu_read_unlock include/linux/rcupdate.h:652 [inline] > filemap_map_pages+0x5b3/0x990 mm/filemap.c:2687 > do_fault_around mm/memory.c:3450 [inline] > do_read_fault mm/memory.c:3484 [inline] > do_fault mm/memory.c:3618 [inline] > handle_pte_fault mm/memory.c:3849 [inline] > __handle_mm_fault+0x2554/0x2cb0 mm/memory.c:3973 > handle_mm_fault+0x21b/0x530 mm/memory.c:4010 > do_user_addr_fault arch/x86/mm/fault.c:1441 [inline] > __do_page_fault+0x3fb/0x9e0 arch/x86/mm/fault.c:1506 > do_page_fault+0x54/0x233 arch/x86/mm/fault.c:1530 > page_fault+0x34/0x40 arch/x86/entry/entry_64.S:1202 > > write to 0xffffffff85a7d440 of 8 bytes by task 7353 on cpu 1: > sync_exp_reset_tree kernel/rcu/tree_exp.h:137 [inline] > sync_rcu_exp_select_cpus+0xd5/0x590 kernel/rcu/tree_exp.h:427 > rcu_exp_sel_wait_wake kernel/rcu/tree_exp.h:575 [inline] > wait_rcu_exp_gp+0x25/0x40 kernel/rcu/tree_exp.h:589 > process_one_work+0x3d4/0x890 kernel/workqueue.c:2269 > worker_thread+0xa0/0x800 kernel/workqueue.c:2415 > kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253 > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352 > > Reported by Kernel Concurrency Sanitizer on: > CPU: 1 PID: 7353 Comm: kworker/1:0 Not tainted 5.4.0-rc3+ #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > Workqueue: rcu_gp wait_rcu_exp_gp > ================================================================== > Kernel panic - not syncing: panic_on_warn set ... > CPU: 1 PID: 7353 Comm: kworker/1:0 Not tainted 5.4.0-rc3+ #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > Workqueue: rcu_gp wait_rcu_exp_gp > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0xf5/0x159 lib/dump_stack.c:113 > panic+0x210/0x640 kernel/panic.c:221 > kcsan_report.cold+0xc/0x10 kernel/kcsan/report.c:302 > __kcsan_setup_watchpoint+0x32e/0x4a0 kernel/kcsan/core.c:411 > __tsan_write8 kernel/kcsan/kcsan.c:36 [inline] > __tsan_write8+0x32/0x40 kernel/kcsan/kcsan.c:36 > sync_exp_reset_tree kernel/rcu/tree_exp.h:137 [inline] > sync_rcu_exp_select_cpus+0xd5/0x590 kernel/rcu/tree_exp.h:427 > rcu_exp_sel_wait_wake kernel/rcu/tree_exp.h:575 [inline] > wait_rcu_exp_gp+0x25/0x40 kernel/rcu/tree_exp.h:589 > process_one_work+0x3d4/0x890 kernel/workqueue.c:2269 > worker_thread+0xa0/0x800 kernel/workqueue.c:2415 > kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253 > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352 > Shutting down cpus with NMI > Kernel Offset: disabled > Rebooting in 86400 seconds.. > > > --- > This bug is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. > > syzbot will keep track of this bug report. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
