[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CACGkMEtRyEkpRetANvU1L97gLtVVT+vaBV1Hmh2QqZu9c9tvYw@mail.gmail.com>
Date: Thu, 3 Aug 2023 11:20:20 +0800
From: Jason Wang <jasowang@...hat.com>
To: Andrew Kanner <andrew.kanner@...il.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
pabeni@...hat.com, netdev@...r.kernel.org, brouer@...hat.com,
dsahern@...il.com, jbrouer@...hat.com, john.fastabend@...il.com,
linux-kernel@...r.kernel.org,
linux-kernel-mentees@...ts.linuxfoundation.org,
syzbot+f817490f5bd20541b90a@...kaller.appspotmail.com
Subject: Re: [PATCH v4 2/2] net: core: remove unnecessary frame_sz check in bpf_xdp_adjust_tail()
On Wed, Aug 2, 2023 at 6:09 AM Andrew Kanner <andrew.kanner@...il.com> wrote:
>
> Syzkaller reported the following issue:
> =======================================
> Too BIG xdp->frame_sz = 131072
> WARNING: CPU: 0 PID: 5020 at net/core/filter.c:4121
> ____bpf_xdp_adjust_tail net/core/filter.c:4121 [inline]
> WARNING: CPU: 0 PID: 5020 at net/core/filter.c:4121
> bpf_xdp_adjust_tail+0x466/0xa10 net/core/filter.c:4103
> ...
> Call Trace:
> <TASK>
> bpf_prog_4add87e5301a4105+0x1a/0x1c
> __bpf_prog_run include/linux/filter.h:600 [inline]
> bpf_prog_run_xdp include/linux/filter.h:775 [inline]
> bpf_prog_run_generic_xdp+0x57e/0x11e0 net/core/dev.c:4721
> netif_receive_generic_xdp net/core/dev.c:4807 [inline]
> do_xdp_generic+0x35c/0x770 net/core/dev.c:4866
> tun_get_user+0x2340/0x3ca0 drivers/net/tun.c:1919
> tun_chr_write_iter+0xe8/0x210 drivers/net/tun.c:2043
> call_write_iter include/linux/fs.h:1871 [inline]
> new_sync_write fs/read_write.c:491 [inline]
> vfs_write+0x650/0xe40 fs/read_write.c:584
> ksys_write+0x12f/0x250 fs/read_write.c:637
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> xdp->frame_sz > PAGE_SIZE check was introduced in commit c8741e2bfe87
> ("xdp: Allow bpf_xdp_adjust_tail() to grow packet size"). But Jesper
> Dangaard Brouer <jbrouer@...hat.com> noted that after introducing the
> xdp_init_buff() which all XDP driver use - it's safe to remove this
> check. The original intend was to catch cases where XDP drivers have
> not been updated to use xdp.frame_sz, but that is not longer a concern
> (since xdp_init_buff).
>
> Running the initial syzkaller repro it was discovered that the
> contiguous physical memory allocation is used for both xdp paths in
> tun_get_user(), e.g. tun_build_skb() and tun_alloc_skb(). It was also
> stated by Jesper Dangaard Brouer <jbrouer@...hat.com> that XDP can
> work on higher order pages, as long as this is contiguous physical
> memory (e.g. a page).
>
> Reported-and-tested-by: syzbot+f817490f5bd20541b90a@...kaller.appspotmail.com
> Closes: https://lore.kernel.org/all/000000000000774b9205f1d8a80d@google.com/T/
> Link: https://syzkaller.appspot.com/bug?extid=f817490f5bd20541b90a
> Link: https://lore.kernel.org/all/20230725155403.796-1-andrew.kanner@gmail.com/T/
> Fixes: 43b5169d8355 ("net, xdp: Introduce xdp_init_buff utility routine")
> Signed-off-by: Andrew Kanner <andrew.kanner@...il.com>
Acked-by: Jason Wang <jasowang@...hat.com>
Thanks
> ---
> net/core/filter.c | 6 ------
> 1 file changed, 6 deletions(-)
>
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 06ba0e56e369..28a59596987a 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -4116,12 +4116,6 @@ BPF_CALL_2(bpf_xdp_adjust_tail, struct xdp_buff *, xdp, int, offset)
> if (unlikely(data_end > data_hard_end))
> return -EINVAL;
>
> - /* ALL drivers MUST init xdp->frame_sz, chicken check below */
> - if (unlikely(xdp->frame_sz > PAGE_SIZE)) {
> - WARN_ONCE(1, "Too BIG xdp->frame_sz = %d\n", xdp->frame_sz);
> - return -EINVAL;
> - }
> -
> if (unlikely(data_end < xdp->data + ETH_HLEN))
> return -EINVAL;
>
> --
> 2.39.3
>
Powered by blists - more mailing lists