#1 Fixed a serious error. #2 Fixed a logical error, but this error did not cause any serious consequences. The logic of this piece is really messy. Fortunately, my refactored patch can be completed with a small amount of testing. Thanks. Xuan Zhuo (2): virtio-net: fix for unable to handle page fault for address virtio_net: get build_skb() buf by data ptr drivers/net/virtio_net.c | 20 ++++++++------------ 1 file changed, 8 insertions(+), 12 deletions(-) -- 2.31.0
Xuan Zhuo
2021-Jun-01 06:39 UTC
[PATCH net v2 1/2] virtio-net: fix for unable to handle page fault for address
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 at linux.alibaba.com>
---
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;
--
2.31.0
Xuan Zhuo
2021-Jun-01 06:40 UTC
[PATCH net v2 2/2] virtio_net: get build_skb() buf by data ptr
In the case of merge, the page passed into page_to_skb() may be a head
page, not the page where the current data is located. So when trying to
get the buf where the data is located, we should get buf based on
headroom instead of offset.
This patch solves this problem. But if you don't use this patch, the
original code can also run, because if the page is not the page of the
current data, the calculated tailroom will be less than 0, and will not
enter the logic of build_skb() . The significance of this patch is to
modify this logical problem, allowing more situations to use
build_skb().
Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com>
---
drivers/net/virtio_net.c | 17 ++++++-----------
1 file changed, 6 insertions(+), 11 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 6b929aca155a..fa407eb8b457 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -401,18 +401,13 @@ static struct sk_buff *page_to_skb(struct virtnet_info
*vi,
/* If headroom is not 0, there is an offset between the beginning of the
* data and the allocated space, otherwise the data and the allocated
* space are aligned.
+ *
+ * Buffers with headroom use PAGE_SIZE as alloc size, see
+ * add_recvbuf_mergeable() + get_mergeable_buf_len()
*/
- if (headroom) {
- /* Buffers with headroom use PAGE_SIZE as alloc size,
- * see add_recvbuf_mergeable() + get_mergeable_buf_len()
- */
- truesize = PAGE_SIZE;
- tailroom = truesize - len - offset;
- buf = page_address(page);
- } else {
- tailroom = truesize - len;
- buf = p;
- }
+ truesize = headroom ? PAGE_SIZE : truesize;
+ tailroom = truesize - len - headroom;
+ buf = p - headroom;
len -= hdr_len;
offset += hdr_padded_len;
--
2.31.0
Michael S. Tsirkin
2021-Jun-01 11:06 UTC
[PATCH net v2 0/2] virtio-net: fix for build_skb()
On Tue, Jun 01, 2021 at 02:39:58PM +0800, Xuan Zhuo wrote:> #1 Fixed a serious error. > #2 Fixed a logical error, but this error did not cause any serious consequences. > > The logic of this piece is really messy. Fortunately, my refactored patch can be > completed with a small amount of testing.Looks good, thanks! Also needed for stable I think. Acked-by: Michael S. Tsirkin <mst at redhat.com>> Thanks. > > Xuan Zhuo (2): > virtio-net: fix for unable to handle page fault for address > virtio_net: get build_skb() buf by data ptr > > drivers/net/virtio_net.c | 20 ++++++++------------ > 1 file changed, 8 insertions(+), 12 deletions(-) > > -- > 2.31.0