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From:   Jens Axboe <axboe@kernel.dk>
Date:   Sun, 14 Apr 2019 09:45:00 -0600
Message-ID: <CAKb3OG_adYHath5LfT66RDy9gsrxvPT7Q10ns6308F9MyEzp6A@mail.gmail.com>
Subject: Re: WARNING in io_uring_setup
To:     syzbot <syzbot+cd714a07c6de2bc34293@syzkaller.appspotmail.com>,
        Hannes Reinecke <hare@suse.com>,
        linux-block <linux-block@vger.kernel.org>,
        fsdevel <linux-fsdevel@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Al Viro <viro@zeniv.linux.org.uk>
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Sender: linux-kernel-owner@vger.kernel.org
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On 4/13/19 9:25 AM, Jens Axboe wrote:
> On 4/13/19 2:26 AM, syzbot wrote:
>> Hello,
>>
>> syzbot found the following crash on:
>>
>> HEAD commit:    8ee15f32 Merge tag 'dma-mapping-5.1-1' of git://git.infrad..
>> git tree:       upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=146b7cd3200000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=4fb64439e07a1ec0
>> dashboard link: https://syzkaller.appspot.com/bug?extid=cd714a07c6de2bc34293
>> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15d8b397200000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10b62ab7200000
>>
>> The bug was bisected to:
>>
>> commit 6c271ce2f1d572f7fa225700a13cfe7ced492434
>> Author: Jens Axboe <axboe@kernel.dk>
>> Date:   Thu Jan 10 18:22:30 2019 +0000
>>
>>      io_uring: add submission polling
>>
>> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=170a286b200000
>> final crash:    https://syzkaller.appspot.com/x/report.txt?x=148a286b200000
>> console output: https://syzkaller.appspot.com/x/log.txt?x=108a286b200000
>>
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+cd714a07c6de2bc34293@syzkaller.appspotmail.com
>> Fixes: 6c271ce2f1d5 ("io_uring: add submission polling")
>>
>> WARNING: CPU: 1 PID: 7600 at include/linux/cpumask.h:121 cpu_max_bits_warn
>> include/linux/cpumask.h:121 [inline]
>> WARNING: CPU: 1 PID: 7600 at include/linux/cpumask.h:121 cpumask_check
>> include/linux/cpumask.h:128 [inline]
>> WARNING: CPU: 1 PID: 7600 at include/linux/cpumask.h:121 cpumask_test_cpu
>> include/linux/cpumask.h:344 [inline]
>> WARNING: CPU: 1 PID: 7600 at include/linux/cpumask.h:121
>> io_sq_offload_start fs/io_uring.c:2244 [inline]
>> WARNING: CPU: 1 PID: 7600 at include/linux/cpumask.h:121 io_uring_create
>> fs/io_uring.c:2851 [inline]
>> WARNING: CPU: 1 PID: 7600 at include/linux/cpumask.h:121
>> io_uring_setup+0x13b2/0x1990 fs/io_uring.c:2903
>> Kernel panic - not syncing: panic_on_warn set ...
>> CPU: 1 PID: 7600 Comm: syz-executor594 Not tainted 5.1.0-rc4+ #65
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>> Google 01/01/2011
>> Call Trace:
>>   __dump_stack lib/dump_stack.c:77 [inline]
>>   dump_stack+0x172/0x1f0 lib/dump_stack.c:113
>>   panic+0x2cb/0x65c kernel/panic.c:214
>>   __warn.cold+0x20/0x45 kernel/panic.c:571
>>   report_bug+0x263/0x2b0 lib/bug.c:186
>>   fixup_bug arch/x86/kernel/traps.c:179 [inline]
>>   fixup_bug arch/x86/kernel/traps.c:174 [inline]
>>   do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
>>   do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
>>   invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
>> RIP: 0010:cpu_max_bits_warn include/linux/cpumask.h:121 [inline]
>> RIP: 0010:cpumask_check include/linux/cpumask.h:128 [inline]
>> RIP: 0010:cpumask_test_cpu include/linux/cpumask.h:344 [inline]
>> RIP: 0010:io_sq_offload_start fs/io_uring.c:2244 [inline]
>> RIP: 0010:io_uring_create fs/io_uring.c:2851 [inline]
>> RIP: 0010:io_uring_setup+0x13b2/0x1990 fs/io_uring.c:2903
>> Code: 00 00 00 00 fc ff df 48 89 da 48 c1 ea 03 80 3c 02 00 0f 84 18 fe ff
>> ff 48 89 df e8 e8 80 e0 ff e9 0b fe ff ff e8 2e 79 a8 ff <0f> 0b e9 db f8
>> ff ff e8 22 79 a8 ff 49 8d 9c 24 88 00 00 00 48 b8
>> RSP: 0018:ffff8880a8eb7dc0 EFLAGS: 00010293
>> RAX: ffff88808cdd8700 RBX: 0000000000000400 RCX: ffffffff81c80eab
>> RDX: 0000000000000000 RSI: ffffffff81c815d2 RDI: 0000000000000005
>> RBP: ffff8880a8eb7ef0 R08: ffff88808cdd8700 R09: ffffed1011c75244
>> R10: ffffed1011c75243 R11: ffff88808e3a921f R12: ffff88808d34a480
>> R13: ffff8880a8eb7ec8 R14: ffff88808d34a4c0 R15: ffff88808d34a4d4
>>   __do_sys_io_uring_setup fs/io_uring.c:2916 [inline]
>>   __se_sys_io_uring_setup fs/io_uring.c:2913 [inline]
>>   __x64_sys_io_uring_setup+0x54/0x80 fs/io_uring.c:2913
>>   do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
>>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>> RIP: 0033:0x440239
>> Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7
>> 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
>> ff 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
>> RSP: 002b:00007fff32156718 EFLAGS: 00000246 ORIG_RAX: 00000000000001a9
>> RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440239
>> RDX: 0000000000400b60 RSI: 0000000020000200 RDI: 0000000000000c9f
>> RBP: 00000000006ca018 R08: 0000000000000000 R09: 0000000000000000
>> R10: 00000000ffffffff R11: 0000000000000246 R12: 0000000000401ac0
>> R13: 0000000000401b50 R14: 0000000000000000 R15: 0000000000000000
>> Kernel Offset: disabled
>> Rebooting in 86400 seconds..
>
> Thanks for the report, below should fix it.

Forgot to include the patch, apparently. Here it is:


diff --git a/fs/io_uring.c b/fs/io_uring.c
index 07d6ef195d05..c9bd17d6571c 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2236,19 +2241,19 @@ static int io_sq_offload_start(struct io_ring_ctx *ctx,
        mmgrab(current->mm);
        ctx->sqo_mm = current->mm;

-       ctx->sq_thread_idle = msecs_to_jiffies(p->sq_thread_idle);
-       if (!ctx->sq_thread_idle)
-               ctx->sq_thread_idle = HZ;
-
-       ret = -EINVAL;
-       if (!cpu_possible(p->sq_thread_cpu))
-               goto err;
-
        if (ctx->flags & IORING_SETUP_SQPOLL) {
+               ctx->sq_thread_idle = msecs_to_jiffies(p->sq_thread_idle);
+               if (!ctx->sq_thread_idle)
+                       ctx->sq_thread_idle = HZ;
+
                if (p->flags & IORING_SETUP_SQ_AFF) {
                        int cpu;

                        cpu = array_index_nospec(p->sq_thread_cpu, NR_CPUS);
+                       ret = -EINVAL;
+                       if (!cpu_possible(p->sq_thread_cpu))
+                               goto err;
+
                        ctx->sqo_thread = kthread_create_on_cpu(io_sq_thread,
                                                        ctx, cpu,
                                                        "io_uring-sq");


--
Jens Axboe