Re: [PATCH net v2 1/2] virtio-net: fix for unable to handle page fault for address

[Jason Wang <jasowang@xxxxxxxxxx>]

在 2021/6/1 下午2:39, Xuan Zhuo 写道:
> In merge mode, when xdp is enabled, if the headroom of buf is smaller
> than virtnet_get_headroom(), xdp_linearize_page() will be called but the
> variable of "headroom" is still 0, which leads to wrong logic after
> entering page_to_skb().
>
> [   16.600944] BUG: unable to handle page fault for address: ffffecbfff7b43c8[   16.602175] #PF: supervisor read access in kernel mode
> [   16.603350] #PF: error_code(0x0000) - not-present page
> [   16.604200] PGD 0 P4D 0
> [   16.604686] Oops: 0000 [#1] SMP PTI
> [   16.605306] CPU: 4 PID: 715 Comm: sh Tainted: G    B             5.12.0+ #312
> [   16.606429] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/04
> [   16.608217] RIP: 0010:unmap_page_range+0x947/0xde0
> [   16.609014] Code: 00 00 08 00 48 83 f8 01 45 19 e4 41 f7 d4 41 83 e4 03 e9 a4 fd ff ff e8 b7 63 ed ff 4c 89 e0 48 c1 e0 065
> [   16.611863] RSP: 0018:ffffc90002503c58 EFLAGS: 00010286
> [   16.612720] RAX: ffffecbfff7b43c0 RBX: 00007f19f7203000 RCX: ffffffff812ff359
> [   16.613853] RDX: ffff888107778000 RSI: 0000000000000000 RDI: 0000000000000005
> [   16.614976] RBP: ffffea000425e000 R08: 0000000000000000 R09: 3030303030303030
> [   16.616124] R10: ffffffff82ed7d94 R11: 6637303030302052 R12: 7c00000afffded0f
> [   16.617276] R13: 0000000000000001 R14: ffff888119ee7010 R15: 00007f19f7202000
> [   16.618423] FS:  0000000000000000(0000) GS:ffff88842fd00000(0000) knlGS:0000000000000000
> [   16.619738] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   16.620670] CR2: ffffecbfff7b43c8 CR3: 0000000103220005 CR4: 0000000000370ee0
> [   16.621792] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [   16.622920] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [   16.624047] Call Trace:
> [   16.624525]  ? release_pages+0x24d/0x730
> [   16.625209]  unmap_single_vma+0xa9/0x130
> [   16.625885]  unmap_vmas+0x76/0xf0
> [   16.626480]  exit_mmap+0xa0/0x210
> [   16.627129]  mmput+0x67/0x180
> [   16.627673]  do_exit+0x3d1/0xf10
> [   16.628259]  ? do_user_addr_fault+0x231/0x840
> [   16.629000]  do_group_exit+0x53/0xd0
> [   16.629631]  __x64_sys_exit_group+0x1d/0x20
> [   16.630354]  do_syscall_64+0x3c/0x80
> [   16.630988]  entry_SYSCALL_64_after_hwframe+0x44/0xae
> [   16.631828] RIP: 0033:0x7f1a043d0191
> [   16.632464] Code: Unable to access opcode bytes at RIP 0x7f1a043d0167.
> [   16.633502] RSP: 002b:00007ffe3d993308 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
> [   16.634737] RAX: ffffffffffffffda RBX: 00007f1a044c9490 RCX: 00007f1a043d0191
> [   16.635857] RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
> [   16.636986] RBP: 0000000000000000 R08: ffffffffffffff88 R09: 0000000000000001
> [   16.638120] R10: 0000000000000008 R11: 0000000000000246 R12: 00007f1a044c9490
> [   16.639245] R13: 0000000000000001 R14: 00007f1a044c9968 R15: 0000000000000000
> [   16.640408] Modules linked in:
> [   16.640958] CR2: ffffecbfff7b43c8
> [   16.641557] ---[ end trace bc4891c6ce46354c ]---
> [   16.642335] RIP: 0010:unmap_page_range+0x947/0xde0
> [   16.643135] Code: 00 00 08 00 48 83 f8 01 45 19 e4 41 f7 d4 41 83 e4 03 e9 a4 fd ff ff e8 b7 63 ed ff 4c 89 e0 48 c1 e0 065
> [   16.645983] RSP: 0018:ffffc90002503c58 EFLAGS: 00010286
> [   16.646845] RAX: ffffecbfff7b43c0 RBX: 00007f19f7203000 RCX: ffffffff812ff359
> [   16.647970] RDX: ffff888107778000 RSI: 0000000000000000 RDI: 0000000000000005
> [   16.649091] RBP: ffffea000425e000 R08: 0000000000000000 R09: 3030303030303030
> [   16.650250] R10: ffffffff82ed7d94 R11: 6637303030302052 R12: 7c00000afffded0f
> [   16.651394] R13: 0000000000000001 R14: ffff888119ee7010 R15: 00007f19f7202000
> [   16.652529] FS:  0000000000000000(0000) GS:ffff88842fd00000(0000) knlGS:0000000000000000
> [   16.653887] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   16.654841] CR2: ffffecbfff7b43c8 CR3: 0000000103220005 CR4: 0000000000370ee0
> [   16.655992] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [   16.657150] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [   16.658290] Kernel panic - not syncing: Fatal exception
> [   16.659613] Kernel Offset: disabled
> [   16.660234] ---[ end Kernel panic - not syncing: Fatal exception ]---
>
> Fixes: fb32856b16ad ("virtio-net: page_to_skb() use build_skb when there's sufficient tailroom")
> Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>


Acked-by: Jason Wang <jasowang@xxxxxxxxxx>


> ---
>   drivers/net/virtio_net.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 9b6a4a875c55..6b929aca155a 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -958,7 +958,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>   				put_page(page);
>   				head_skb = page_to_skb(vi, rq, xdp_page, offset,
>   						       len, PAGE_SIZE, false,
> -						       metasize, headroom);
> +						       metasize,
> +						       VIRTIO_XDP_HEADROOM);
>   				return head_skb;
>   			}
>   			break;

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