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Subject[PATCH] tun: make tun_build_skb() thread safe
Date
From: Eric Dumazet <eric.dumazet@gmail.com>

tun_build_skb() is not thread safe since it uses per queue page frag,
this will break things when multiple threads are sending through same
queue. Switch to use per-thread generator (no lock involved).

Fixes: 66ccbc9c87c2 ("tap: use build_skb() for small packet")
Tested-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
drivers/net/tun.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 5892284..c38cd84 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -175,7 +175,6 @@ struct tun_file {
struct list_head next;
struct tun_struct *detached;
struct skb_array tx_array;
- struct page_frag alloc_frag;
};

struct tun_flow_entry {
@@ -578,8 +577,6 @@ static void __tun_detach(struct tun_file *tfile, bool clean)
}
if (tun)
skb_array_cleanup(&tfile->tx_array);
- if (tfile->alloc_frag.page)
- put_page(tfile->alloc_frag.page);
sock_put(&tfile->sk);
}
}
@@ -1272,7 +1269,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
struct virtio_net_hdr *hdr,
int len, int *generic_xdp)
{
- struct page_frag *alloc_frag = &tfile->alloc_frag;
+ struct page_frag *alloc_frag = &current->task_frag;
struct sk_buff *skb;
struct bpf_prog *xdp_prog;
int buflen = SKB_DATA_ALIGN(len + TUN_RX_PAD) +
@@ -2580,8 +2577,6 @@ static int tun_chr_open(struct inode *inode, struct file * file)
tfile->sk.sk_write_space = tun_sock_write_space;
tfile->sk.sk_sndbuf = INT_MAX;

- tfile->alloc_frag.page = NULL;
-
file->private_data = tfile;
INIT_LIST_HEAD(&tfile->next);

--
2.7.4
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