Message-ID: <d5844c03-fa61-d256-be0d-b40446414299@gmail.com>
Date:   Sun, 2 May 2021 23:12:31 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Palash Oswal <oswalpalash@...il.com>, Jens Axboe <axboe@...nel.dk>,
        io-uring@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        syzbot+11bf59db879676f59e52@...kaller.appspotmail.com
Subject: Re: INFO: task hung in io_uring_cancel_sqpoll

On 4/30/21 3:21 PM, Palash Oswal wrote:
> On Thursday, March 18, 2021 at 9:40:21 PM UTC+5:30 syzbot wrote:
>>
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit: 0d7588ab riscv: process: Fix no prototype for arch_dup_tas..
>> git tree: git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux.git fixes
>> console output: https://syzkaller.appspot.com/x/log.txt?x=12dde5aed00000
>> kernel config: https://syzkaller.appspot.com/x/.config?x=81c0b708b31626cc
>> dashboard link: https://syzkaller.appspot.com/bug?extid=11bf59db879676f59e52
>> userspace arch: riscv64
>> CC: [asml.s...@...il.com ax...@...nel.dk io-u...@...r.kernel.org linux-...@...r.kernel.org]
>>
>> 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+11bf59...@...kaller.appspotmail.com
>>
>> INFO: task iou-sqp-4867:4871 blocked for more than 430 seconds.
>> Not tainted 5.12.0-rc2-syzkaller-00467-g0d7588ab9ef9 #0
>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>> task:iou-sqp-4867 state:D stack: 0 pid: 4871 ppid: 4259 flags:0x00000004
>> Call Trace:
>> [<ffffffe003bc3252>] context_switch kernel/sched/core.c:4324 [inline]
>> [<ffffffe003bc3252>] __schedule+0x478/0xdec kernel/sched/core.c:5075
>> [<ffffffe003bc3c2a>] schedule+0x64/0x166 kernel/sched/core.c:5154
>> [<ffffffe0004b80ee>] io_uring_cancel_sqpoll+0x1de/0x294 fs/io_uring.c:8858
>> [<ffffffe0004c19cc>] io_sq_thread+0x548/0xe58 fs/io_uring.c:6750
>> [<ffffffe000005570>] ret_from_exception+0x0/0x14

The test might be very useful. Would you send a patch to
liburing? Or mind the repro being taken as a test?


>>
>> Showing all locks held in the system:
>> 3 locks held by kworker/u4:0/7:
>> 3 locks held by kworker/1:0/19:
>> 1 lock held by khungtaskd/1556:
>> #0: ffffffe00592b5e8 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x32/0x1fa kernel/locking/lockdep.c:6329
>> 1 lock held by klogd/3947:
>> 2 locks held by getty/4142:
>> #0: ffffffe00f1aa098 (&tty->ldisc_sem){++++}-{0:0}, at: ldsem_down_read+0x3c/0x48 drivers/tty/tty_ldsem.c:340
>> #1: ffffffd010b6f2e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x9ac/0xb08 drivers/tty/n_tty.c:2178
>> 2 locks held by kworker/0:1/4375:
>>
>> =============================================
>>
>>
>>
>> ---
>> This report 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 syzk...@...glegroups.com.
>>
>> syzbot will keep track of this issue. See:
>> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> 
> Attaching a C reproducer for this bug:
> 
> #define _GNU_SOURCE
> 
> #include <fcntl.h>
> #include <signal.h>
> #include <stdint.h>
> #include <stdlib.h>
> #include <string.h>
> #include <sys/mman.h>
> #include <sys/syscall.h>
> #include <sys/wait.h>
> #include <time.h>
> #include <unistd.h>
> 
> static uint64_t current_time_ms(void)
> {
>     struct timespec ts;
>     if (clock_gettime(CLOCK_MONOTONIC, &ts))
>         exit(1);
>     return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000;
> }
> 
> #define SIZEOF_IO_URING_SQE 64
> #define SIZEOF_IO_URING_CQE 16
> #define SQ_TAIL_OFFSET 64
> #define SQ_RING_MASK_OFFSET 256
> #define SQ_RING_ENTRIES_OFFSET 264
> #define CQ_RING_ENTRIES_OFFSET 268
> #define CQ_CQES_OFFSET 320
> 
> struct io_sqring_offsets {
>     uint32_t head;
>     uint32_t tail;
>     uint32_t ring_mask;
>     uint32_t ring_entries;
>     uint32_t flags;
>     uint32_t dropped;
>     uint32_t array;
>     uint32_t resv1;
>     uint64_t resv2;
> };
> 
> struct io_cqring_offsets {
>     uint32_t head;
>     uint32_t tail;
>     uint32_t ring_mask;
>     uint32_t ring_entries;
>     uint32_t overflow;
>     uint32_t cqes;
>     uint64_t resv[2];
> };
> 
> struct io_uring_params {
>     uint32_t sq_entries;
>     uint32_t cq_entries;
>     uint32_t flags;
>     uint32_t sq_thread_cpu;
>     uint32_t sq_thread_idle;
>     uint32_t features;
>     uint32_t resv[4];
>     struct io_sqring_offsets sq_off;
>     struct io_cqring_offsets cq_off;
> };
> 
> #define IORING_OFF_SQ_RING 0
> #define IORING_OFF_SQES 0x10000000ULL
> 
> #define sys_io_uring_setup 425
> static long syz_io_uring_setup(volatile long a0, volatile long a1,
> volatile long a2, volatile long a3, volatile long a4, volatile long
> a5)
> {
>     uint32_t entries = (uint32_t)a0;
>     struct io_uring_params* setup_params = (struct io_uring_params*)a1;
>     void* vma1 = (void*)a2;
>     void* vma2 = (void*)a3;
>     void** ring_ptr_out = (void**)a4;
>     void** sqes_ptr_out = (void**)a5;
>     uint32_t fd_io_uring = syscall(sys_io_uring_setup, entries, setup_params);
>     uint32_t sq_ring_sz = setup_params->sq_off.array +
> setup_params->sq_entries * sizeof(uint32_t);
>     uint32_t cq_ring_sz = setup_params->cq_off.cqes +
> setup_params->cq_entries * SIZEOF_IO_URING_CQE;
>     uint32_t ring_sz = sq_ring_sz > cq_ring_sz ? sq_ring_sz : cq_ring_sz;
>     *ring_ptr_out = mmap(vma1, ring_sz, PROT_READ | PROT_WRITE,
> MAP_SHARED | MAP_POPULATE | MAP_FIXED, fd_io_uring,
> IORING_OFF_SQ_RING);
>     uint32_t sqes_sz = setup_params->sq_entries * SIZEOF_IO_URING_SQE;
>     *sqes_ptr_out = mmap(vma2, sqes_sz, PROT_READ | PROT_WRITE,
> MAP_SHARED | MAP_POPULATE | MAP_FIXED, fd_io_uring, IORING_OFF_SQES);
>     return fd_io_uring;
> }
> 
> static long syz_io_uring_submit(volatile long a0, volatile long a1,
> volatile long a2, volatile long a3)
> {
>     char* ring_ptr = (char*)a0;
>     char* sqes_ptr = (char*)a1;
>     char* sqe = (char*)a2;
>     uint32_t sqes_index = (uint32_t)a3;
>     uint32_t sq_ring_entries = *(uint32_t*)(ring_ptr + SQ_RING_ENTRIES_OFFSET);
>     uint32_t cq_ring_entries = *(uint32_t*)(ring_ptr + CQ_RING_ENTRIES_OFFSET);
>     uint32_t sq_array_off = (CQ_CQES_OFFSET + cq_ring_entries *
> SIZEOF_IO_URING_CQE + 63) & ~63;
>     if (sq_ring_entries)
>         sqes_index %= sq_ring_entries;
>     char* sqe_dest = sqes_ptr + sqes_index * SIZEOF_IO_URING_SQE;
>     memcpy(sqe_dest, sqe, SIZEOF_IO_URING_SQE);
>     uint32_t sq_ring_mask = *(uint32_t*)(ring_ptr + SQ_RING_MASK_OFFSET);
>     uint32_t* sq_tail_ptr = (uint32_t*)(ring_ptr + SQ_TAIL_OFFSET);
>     uint32_t sq_tail = *sq_tail_ptr & sq_ring_mask;
>     uint32_t sq_tail_next = *sq_tail_ptr + 1;
>     uint32_t* sq_array = (uint32_t*)(ring_ptr + sq_array_off);
>     *(sq_array + sq_tail) = sqes_index;
>     __atomic_store_n(sq_tail_ptr, sq_tail_next, __ATOMIC_RELEASE);
>     return 0;
> }
> 
> static void kill_and_wait(int pid, int* status)
> {
>     kill(-pid, SIGKILL);
>     kill(pid, SIGKILL);
>     while (waitpid(-1, status, __WALL) != pid) {
>     }
> }
> 
> #define WAIT_FLAGS __WALL
> 
> uint64_t r[3] = {0xffffffffffffffff, 0x0, 0x0};
> 
> void trigger_bug(void)
> {
>     intptr_t res = 0;
>     *(uint32_t*)0x20000204 = 0;
>     *(uint32_t*)0x20000208 = 2;
>     *(uint32_t*)0x2000020c = 0;
>     *(uint32_t*)0x20000210 = 0;
>     *(uint32_t*)0x20000218 = -1;
>     memset((void*)0x2000021c, 0, 12);
>     res = -1;
>     res = syz_io_uring_setup(0x7987, 0x20000200, 0x20400000,
> 0x20ffd000, 0x200000c0, 0x200001c0);
>     if (res != -1) {
>         r[0] = res;
>         r[1] = *(uint64_t*)0x200000c0;
>         r[2] = *(uint64_t*)0x200001c0;
>     }
>     *(uint8_t*)0x20000180 = 0xb;
>     *(uint8_t*)0x20000181 = 1;
>     *(uint16_t*)0x20000182 = 0;
>     *(uint32_t*)0x20000184 = 0;
>     *(uint64_t*)0x20000188 = 4;
>     *(uint64_t*)0x20000190 = 0x20000140;
>     *(uint64_t*)0x20000140 = 0x77359400;
>     *(uint64_t*)0x20000148 = 0;
>     *(uint32_t*)0x20000198 = 1;
>     *(uint32_t*)0x2000019c = 0;
>     *(uint64_t*)0x200001a0 = 0;
>     *(uint16_t*)0x200001a8 = 0;
>     *(uint16_t*)0x200001aa = 0;
>     memset((void*)0x200001ac, 0, 20);
>     syz_io_uring_submit(r[1], r[2], 0x20000180, 1);
>     *(uint32_t*)0x20000544 = 0;
>     *(uint32_t*)0x20000548 = 0x36;
>     *(uint32_t*)0x2000054c = 0;
>     *(uint32_t*)0x20000550 = 0;
>     *(uint32_t*)0x20000558 = r[0];
>     memset((void*)0x2000055c, 0, 12);
>     syz_io_uring_setup(0x4bf1, 0x20000540, 0x20ffd000, 0x20ffc000, 0, 0);
> 
> }
> int main(void)
> {
>     syscall(__NR_mmap, 0x20000000ul, 0x1000000ul, 7ul, 0x32ul, -1, 0ul);
>     int pid = fork();
>     if (pid < 0)
>         exit(1);
>     if (pid == 0) {
>         trigger_bug();
>         exit(0);
>     }
>     int status = 0;
>     uint64_t start = current_time_ms();
>     for (;;) {
>         if (current_time_ms() - start < 1000) {
>             continue;
>         }
>         kill_and_wait(pid, &status);
>         break;
>     }
>     return 0;
> }
> 

-- 
Pavel Begunkov

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