On Mon, 31 May 2021 11:50:00 +0800, Jason Wang <jasowang@xxxxxxxxxx> wrote:
>
> 在 2021/5/14 下午11:16, 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: Michael S. Tsirkin <mst@xxxxxxxxxx>
> > ---
> > drivers/net/virtio_net.c | 12 ++++++------
> > 1 file changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 9b6a4a875c55..3e46c12dde08 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -380,7 +380,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> > struct page *page, unsigned int offset,
> > unsigned int len, unsigned int truesize,
> > bool hdr_valid, unsigned int metasize,
> > - unsigned int headroom)
> > + bool whole_page)
> > {
> > struct sk_buff *skb;
> > struct virtio_net_hdr_mrg_rxbuf *hdr;
> > @@ -398,12 +398,12 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> > else
> > hdr_padded_len = sizeof(struct padded_vnet_hdr);
> >
> > - /* If headroom is not 0, there is an offset between the beginning of the
> > + /* If whole_page, there is an offset between the beginning of the
> > * data and the allocated space, otherwise the data and the allocated
> > * space are aligned.
> > */
> > - if (headroom) {
> > - /* Buffers with headroom use PAGE_SIZE as alloc size,
> > + if (whole_page) {
> > + /* Buffers with whole_page use PAGE_SIZE as alloc size,
> > * see add_recvbuf_mergeable() + get_mergeable_buf_len()
> > */
> > truesize = PAGE_SIZE;
> > @@ -958,7 +958,7 @@ 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, true);
> > return head_skb;
>
>
> Patch looks correct but I'd rather go with a much simple one:
>
> How about just use VIRTNET_XDP_HEADROOM instead of headroom here?
>
> Thanks
OK.
Thanks.
>
>
> > }
> > break;
> > @@ -1016,7 +1016,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> > }
> >
> > head_skb = page_to_skb(vi, rq, page, offset, len, truesize, !xdp_prog,
> > - metasize, headroom);
> > + metasize, !!headroom);
> > curr_skb = head_skb;
> >
> > if (unlikely(!curr_skb))
>
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