* [PATCH net-next v5 2/2] net: core: remove unnecessary frame_sz check in bpf_xdp_adjust_tail()
2023-08-03 18:59 [PATCH net-next v5 1/2] drivers: net: prevent tun_build_skb() to exceed the packet size limit Andrew Kanner
@ 2023-08-03 19:03 ` Andrew Kanner
2023-08-08 2:20 ` [PATCH net-next v5 1/2] drivers: net: prevent tun_build_skb() to exceed the packet size limit patchwork-bot+netdevbpf
1 sibling, 0 replies; 3+ messages in thread
From: Andrew Kanner @ 2023-08-03 19:03 UTC (permalink / raw)
To: ast, daniel, andrii, martin.lau, song, yhs, kpsingh, sdf, haoluo,
jolsa, mw, shayagr, bpf, netdev, linux-kernel
Cc: davem, edumazet, kuba, pabeni, jasowang, hawk, jbrouer, dsahern,
john.fastabend, linux-kernel-mentees, syzbot+f817490f5bd20541b90a,
Andrew Kanner
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>
Acked-by: Jason Wang <jasowang@redhat.com>
---
Notes (akanner):
v5:
- same as v4, but cc-ed bpf@vger.kernel.org according to v3->v4
change
v4: https://lore.kernel.org/all/20230801220710.464-1-andrew.kanner@gmail.com/T/
- remove bpf_xdp_adjust_tail() check for frame_sz instead.
v3: https://lore.kernel.org/all/20230725155403.796-1-andrew.kanner@gmail.com/T/
v2: https://lore.kernel.org/all/20230725153941.653-1-andrew.kanner@gmail.com/T/
v1: https://lore.kernel.org/all/20230724221326.384-1-andrew.kanner@gmail.com/T/
- initial attempts to fix drivers/net/tun.c:tun_get_user(),
e.g. tun_build_skb() or tun_alloc_skb(), to not exceed
xdp->frame_sz check from net/core/filter.c
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
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH net-next v5 1/2] drivers: net: prevent tun_build_skb() to exceed the packet size limit
2023-08-03 18:59 [PATCH net-next v5 1/2] drivers: net: prevent tun_build_skb() to exceed the packet size limit Andrew Kanner
2023-08-03 19:03 ` [PATCH net-next v5 2/2] net: core: remove unnecessary frame_sz check in bpf_xdp_adjust_tail() Andrew Kanner
@ 2023-08-08 2:20 ` patchwork-bot+netdevbpf
1 sibling, 0 replies; 3+ messages in thread
From: patchwork-bot+netdevbpf @ 2023-08-08 2:20 UTC (permalink / raw)
To: Andrew Kanner
Cc: davem, edumazet, kuba, pabeni, jasowang, netdev, hawk, jbrouer,
dsahern, john.fastabend, linux-kernel, linux-kernel-mentees,
syzbot+f817490f5bd20541b90a
Hello:
This series was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:
On Thu, 3 Aug 2023 20:59:48 +0200 you wrote:
> Using the syzkaller repro with reduced packet size it was discovered
> that XDP_PACKET_HEADROOM is not checked in tun_can_build_skb(),
> although pad may be incremented in tun_build_skb(). This may end up
> with exceeding the PAGE_SIZE limit in tun_build_skb().
>
> Jason Wang <jasowang@redhat.com> proposed to count XDP_PACKET_HEADROOM
> always (e.g. without rcu_access_pointer(tun->xdp_prog)) in
> tun_can_build_skb() since there's a window during which XDP program
> might be attached between tun_can_build_skb() and tun_build_skb().
>
> [...]
Here is the summary with links:
- [net-next,v5,1/2] drivers: net: prevent tun_build_skb() to exceed the packet size limit
https://git.kernel.org/netdev/net/c/59eeb2329405
- [net-next,v5,2/2] net: core: remove unnecessary frame_sz check in bpf_xdp_adjust_tail()
https://git.kernel.org/netdev/net/c/d14eea09edf4
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html
^ permalink raw reply [flat|nested] 3+ messages in thread