netdev - Re: [PATCH bpf] xsk: silence warning on memory allocation failure

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Date:   Mon, 11 Jun 2018 15:44:47 -0700
From:   Y Song <ys114321@...il.com>
To:     Björn Töpel <bjorn.topel@...il.com>
Cc:     magnus.karlsson@...el.com, magnus.karlsson@...il.com,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        netdev <netdev@...r.kernel.org>,
        Björn Töpel <bjorn.topel@...el.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        syzkaller-bugs@...glegroups.com,
        syzbot+4abadc5d69117b346506@...kaller.appspotmail.com
Subject: Re: [PATCH bpf] xsk: silence warning on memory allocation failure

On Mon, Jun 11, 2018 at 4:57 AM, Björn Töpel <bjorn.topel@...il.com> wrote:
> From: Björn Töpel <bjorn.topel@...el.com>
>
> syzkaller reported a warning from xdp_umem_pin_pages():
>
>   WARNING: CPU: 1 PID: 4537 at mm/slab_common.c:996 kmalloc_slab+0x56/0x70 mm/slab_common.c:996
>   ...
>   __do_kmalloc mm/slab.c:3713 [inline]
>   __kmalloc+0x25/0x760 mm/slab.c:3727
>   kmalloc_array include/linux/slab.h:634 [inline]
>   kcalloc include/linux/slab.h:645 [inline]
>   xdp_umem_pin_pages net/xdp/xdp_umem.c:205 [inline]
>   xdp_umem_reg net/xdp/xdp_umem.c:318 [inline]
>   xdp_umem_create+0x5c9/0x10f0 net/xdp/xdp_umem.c:349
>   xsk_setsockopt+0x443/0x550 net/xdp/xsk.c:531
>   __sys_setsockopt+0x1bd/0x390 net/socket.c:1935
>   __do_sys_setsockopt net/socket.c:1946 [inline]
>   __se_sys_setsockopt net/socket.c:1943 [inline]
>   __x64_sys_setsockopt+0xbe/0x150 net/socket.c:1943
>   do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> This is a warning about attempting to allocate more than
> KMALLOC_MAX_SIZE memory. The request originates from userspace, and if
> the request is too big, the kernel is free to deny its allocation. In
> this patch, the failed allocation attempt is silenced with
> __GFP_NOWARN.
>
> Fixes: c0c77d8fb787 ("xsk: add user memory registration support sockopt")
> Reported-by: syzbot+4abadc5d69117b346506@...kaller.appspotmail.com
> Signed-off-by: Björn Töpel <bjorn.topel@...el.com>

Acked-by: Yonghong Song <yhs@...com>