diff mbox series

[v4,2/2] net: core: remove unnecessary frame_sz check in bpf_xdp_adjust_tail()

Message ID 20230801220710.464-2-andrew.kanner@gmail.com
State New
Headers
Series [v4,1/2] drivers: net: prevent tun_build_skb() to exceed the packet size limit |

Commit Message

Andrew Kanner Aug. 1, 2023, 10:07 p.m. UTC 
  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@redhat.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@redhat.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@syzkaller.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@gmail.com>
---
 net/core/filter.c | 6 ------
 1 file changed, 6 deletions(-)

Comments

Jesper Dangaard Brouer Aug. 2, 2023, 1:56 p.m. UTC | #1 
On 02/08/2023 00.07, Andrew Kanner 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@redhat.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@redhat.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@syzkaller.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@gmail.com>
> ---

Acked-by: Jesper Dangaard Brouer <hawk@kernel.org>

You can include that ACK in V5.

>   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;
>
Jason Wang Aug. 3, 2023, 3:20 a.m. UTC | #2 
On Wed, Aug 2, 2023 at 6:09 AM Andrew Kanner <andrew.kanner@gmail.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@redhat.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@redhat.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@syzkaller.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@gmail.com>

Acked-by: Jason Wang <jasowang@redhat.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
>
Andrew Kanner Aug. 3, 2023, 6:06 p.m. UTC | #3 
On Thu, Aug 03, 2023 at 11:20:20AM +0800, Jason Wang wrote:
> 
> Acked-by: Jason Wang <jasowang@redhat.com>
> 
> Thanks
> 

Thanks, Jason.
I will use this tag in v5, if you don't mind.
PATCH 2/2 will be the same but with more recipients.
diff mbox series

Patch

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;