Re: linux v5.18.3 fails to boot

[John David Anglin <dave.anglin@bell.net>]

I did a regression search. e039c0b5985999b150594126225e1ee51df7b4c9 is the first bad commit

commit e039c0b5985999b150594126225e1ee51df7b4c9
Author: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Date:   Fri Apr 29 14:38:01 2022 -0700

     list: fix a data-race around ep->rdllist

     [ Upstream commit d679ae94fdd5d3ab00c35078f5af5f37e068b03d ]

     ep_poll() first calls ep_events_available() with no lock held and checks
     if ep->rdllist is empty by list_empty_careful(), which reads
     rdllist->prev.  Thus all accesses to it need some protection to avoid
     store/load-tearing.

     Note INIT_LIST_HEAD_RCU() already has the annotation for both prev
     and next.

     Commit bf3b9f6372c4 ("epoll: Add busy poll support to epoll with socket
     fds.") added the first lockless ep_events_available(), and commit
     c5a282e9635e ("fs/epoll: reduce the scope of wq lock in epoll_wait()")
     made some ep_events_available() calls lockless and added single call under
     a lock, finally commit e59d3c64cba6 ("epoll: eliminate unnecessary lock
     for zero timeout") made the last ep_events_available() lockless.

     BUG: KCSAN: data-race in do_epoll_wait / do_epoll_wait

     write to 0xffff88810480c7d8 of 8 bytes by task 1802 on cpu 0:
      INIT_LIST_HEAD include/linux/list.h:38 [inline]
      list_splice_init include/linux/list.h:492 [inline]
      ep_start_scan fs/eventpoll.c:622 [inline]
      ep_send_events fs/eventpoll.c:1656 [inline]
      ep_poll fs/eventpoll.c:1806 [inline]
      do_epoll_wait+0x4eb/0xf40 fs/eventpoll.c:2234
      do_epoll_pwait fs/eventpoll.c:2268 [inline]
      __do_sys_epoll_pwait fs/eventpoll.c:2281 [inline]
      __se_sys_epoll_pwait+0x12b/0x240 fs/eventpoll.c:2275
      __x64_sys_epoll_pwait+0x74/0x80 fs/eventpoll.c:2275
      do_syscall_x64 arch/x86/entry/common.c:50 [inline]
      do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
      entry_SYSCALL_64_after_hwframe+0x44/0xae

     read to 0xffff88810480c7d8 of 8 bytes by task 1799 on cpu 1:
      list_empty_careful include/linux/list.h:329 [inline]
      ep_events_available fs/eventpoll.c:381 [inline]
      ep_poll fs/eventpoll.c:1797 [inline]
      do_epoll_wait+0x279/0xf40 fs/eventpoll.c:2234
      do_epoll_pwait fs/eventpoll.c:2268 [inline]
      __do_sys_epoll_pwait fs/eventpoll.c:2281 [inline]
      __se_sys_epoll_pwait+0x12b/0x240 fs/eventpoll.c:2275
      __x64_sys_epoll_pwait+0x74/0x80 fs/eventpoll.c:2275
      do_syscall_x64 arch/x86/entry/common.c:50 [inline]
      do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
      entry_SYSCALL_64_after_hwframe+0x44/0xae

     value changed: 0xffff88810480c7d0 -> 0xffff888103c15098

     Reported by Kernel Concurrency Sanitizer on:
     CPU: 1 PID: 1799 Comm: syz-fuzzer Tainted: G        W 5.17.0-rc7-syzkaller-dirty #0
     Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

     Link: https://lkml.kernel.org/r/20220322002653.33865-3-kuniyu@amazon.co.jp
     Fixes: e59d3c64cba6 ("epoll: eliminate unnecessary lock for zero timeout")
     Fixes: c5a282e9635e ("fs/epoll: reduce the scope of wq lock in epoll_wait()")
     Fixes: bf3b9f6372c4 ("epoll: Add busy poll support to epoll with socket fds.")
     Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
     Reported-by: syzbot+bdd6e38a1ed5ee58d8bd@syzkaller.appspotmail.com
     Cc: Al Viro <viro@zeniv.linux.org.uk>, Andrew Morton <akpm@linux-foundation.org>
     Cc: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
     Cc: Kuniyuki Iwashima <kuni1840@gmail.com>
     Cc: "Soheil Hassas Yeganeh" <soheil@google.com>
     Cc: Davidlohr Bueso <dave@stgolabs.net>
     Cc: "Sridhar Samudrala" <sridhar.samudrala@intel.com>
     Cc: Alexander Duyck <alexander.h.duyck@intel.com>
     Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
     Signed-off-by: Sasha Levin <sashal@kernel.org>

  include/linux/list.h | 6 +++---
  1 file changed, 3 insertions(+), 3 deletions(-)

Reverting above change fixes v5.18.3 boot.

It seems the most significant byte of the "ldd -10(r3),rp" instruction in mpt_reply has been
set to 0:

     4084:       bf 80 21 18     cmpb,*<> r0,ret0,4118 <mpt_reply+0x1b8>
     4088:       08 04 02 5b     copy r4,dp
     408c:       00 00 04 00     sync
     4090:       0c 61 10 c2     ldd -10(r3),rp

See IIR value in crash output.

On 2022-06-09 2:13 p.m., John David Anglin wrote:
> [...]
> ata3: SATA link down (SStatus 0 SControl 0)
>       _______________________________
>      < Your System ate a SPARC! Gah! >
>       -------------------------------
>              \   ^__^
>                  (__)\       )\/\
>                   U  ||----w |
>                      ||     ||
> swapper/0 (pid 0): Illegal instruction (code 8)
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.18.3+ #1
> Hardware name: 9000/785/C8000
>
>      YZrvWESTHLNXBCVMcbcbcbcbOGFRQPDI
> PSW: 00001000000001000001101100001110 Not tainted
> r00-03  0000000008041b0e 000000004e8045b0 0000000010bbda78 000000004e804470
> r04-07  0000000010bb5000 0000000000001440 0000000054355000 0000000000001400
> r08-11  0000000055000000 000000000000000e 000000000000000f 0000000055002800
> r12-15  0000000000000000 0000000055002800 0000000040b668c0 0000000040b668c0
> r16-19  0000000000000001 0000000000000001 0000000051b799f0 0000000000000000
> r20-23  0000000000000001 fffffffffffff5b9 0000000000000000 0000000000200000
> r24-27  000000000000000c 000000000800000e 0000000054355144 0000000040b3e0c0
> r28-31  0000000000010001 000000004e804620 000000004e8045b0 0000000040edd040
> sr00-03  00000000000a5c00 0000000000000000 0000000000000000 00000000000a5c00
> sr04-07  0000000000000000 0000000000000000 0000000000000000 0000000000000000
>
> IASQ: 0000000000000000 0000000000000000 IAOQ: 0000000010bbd9e0 0000000010bbd9e4
>  IIR: 006110c2    ISR: 0000000010240000  IOR: 00000003b76dd048
>  CPU:        0   CR30: 0000000040edd040 CR31: ffffffffffffffff
>  ORIG_R28: 0000000000000000
>  IAOQ[0]: mpt_reply+0x130/0x4f0 [mptbase]
>  IAOQ[1]: mpt_reply+0x134/0x4f0 [mptbase]
>  RP(r2): mpt_reply+0x1c8/0x4f0 [mptbase]
> Backtrace:
>  [<0000000010bbde24>] mpt_interrupt+0x84/0xe8 [mptbase]
>  [<000000004026dd64>] __handle_irq_event_percpu+0xc4/0x250
>  [<000000004026df28>] handle_irq_event_percpu+0x38/0xd8
>  [<00000000402776c4>] handle_percpu_irq+0xb4/0xf0
>  [<000000004026c90c>] generic_handle_irq+0x5c/0x90
>  [<00000000401a20e4>] call_on_stack+0x18/0x24
>
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.18.3+ #1
> Hardware name: 9000/785/C8000
> Backtrace:
>  [<00000000401a8cd8>] show_stack+0x70/0x90
>  [<0000000040a8e238>] dump_stack_lvl+0xd8/0x128
>  [<0000000040a8e2bc>] dump_stack+0x34/0x48
>  [<00000000401a8efc>] die_if_kernel+0x1e4/0x3f8
>  [<00000000401a9af4>] handle_interruption+0x59c/0xb58
>  [<00000000401a107c>] intr_check_sig+0x0/0x3c
>
> Kernel panic - not syncing: Fatal exception in interrupt
>
> v5.18.2 with similar config is okay.  The fault seems consistent. IIR contains illegal instruction.
>
> Attached config.
>
> Dave
>


-- 
John David Anglin  dave.anglin@bell.net