linux-kernel - Re: [PATCH -next] io_uring: Fix undefined-behaviour in io_issue

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Date:   Sat, 27 Nov 2021 06:45:15 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Ye Bin <yebin10@...wei.com>, asml.silence@...il.com,
        io-uring@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] io_uring: Fix undefined-behaviour in io_issue_sqe

On 11/17/21 6:59 PM, Ye Bin wrote:
> We got issue as follows:
> ================================================================================
> UBSAN: Undefined behaviour in ./include/linux/ktime.h:42:14
> signed integer overflow:
> -4966321760114568020 * 1000000000 cannot be represented in type 'long long int'
> CPU: 1 PID: 2186 Comm: syz-executor.2 Not tainted 4.19.90+ #12
> Hardware name: linux,dummy-virt (DT)
> Call trace:
>  dump_backtrace+0x0/0x3f0 arch/arm64/kernel/time.c:78
>  show_stack+0x28/0x38 arch/arm64/kernel/traps.c:158
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x170/0x1dc lib/dump_stack.c:118
>  ubsan_epilogue+0x18/0xb4 lib/ubsan.c:161
>  handle_overflow+0x188/0x1dc lib/ubsan.c:192
>  __ubsan_handle_mul_overflow+0x34/0x44 lib/ubsan.c:213
>  ktime_set include/linux/ktime.h:42 [inline]
>  timespec64_to_ktime include/linux/ktime.h:78 [inline]
>  io_timeout fs/io_uring.c:5153 [inline]
>  io_issue_sqe+0x42c8/0x4550 fs/io_uring.c:5599
>  __io_queue_sqe+0x1b0/0xbc0 fs/io_uring.c:5988
>  io_queue_sqe+0x1ac/0x248 fs/io_uring.c:6067
>  io_submit_sqe fs/io_uring.c:6137 [inline]
>  io_submit_sqes+0xed8/0x1c88 fs/io_uring.c:6331
>  __do_sys_io_uring_enter fs/io_uring.c:8170 [inline]
>  __se_sys_io_uring_enter fs/io_uring.c:8129 [inline]
>  __arm64_sys_io_uring_enter+0x490/0x980 fs/io_uring.c:8129
>  invoke_syscall arch/arm64/kernel/syscall.c:53 [inline]
>  el0_svc_common+0x374/0x570 arch/arm64/kernel/syscall.c:121
>  el0_svc_handler+0x190/0x260 arch/arm64/kernel/syscall.c:190
>  el0_svc+0x10/0x218 arch/arm64/kernel/entry.S:1017
> ================================================================================
> 
> As ktime_set only judge 'secs' if big than KTIME_SEC_MAX, but if we pass
> negative value maybe lead to overflow.
> To address this issue, we must check if 'sec' is negative.
> 
> Signed-off-by: Ye Bin <yebin10@...wei.com>
> ---
>  fs/io_uring.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index f9e720595860..d8a6446a7921 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -6157,6 +6157,9 @@ static int io_timeout_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe,
>  	if (get_timespec64(&data->ts, u64_to_user_ptr(sqe->addr)))
>  		return -EFAULT;
>  
> +	if (data->ts.tv_sec < 0 || data->ts.tv_nsec < 0)
> +		return -EINVAL;
> +
>  	data->mode = io_translate_timeout_mode(flags);
>  	hrtimer_init(&data->timer, io_timeout_get_clock(data), data->mode);

This seems to only fix one instance of when a timespec is copied in, what
about the ones in io_timeout_remove_prep()?

-- 
Jens Axboe