Re: [PATCH v2 net 1/2] tuntap: correctly linearize skb when zerocopy is used

[Michael S. Tsirkin]

On Wed, Jul 10, 2013 at 01:43:27PM +0800, Jason Wang wrote:
> Userspace may produce vectors greater than MAX_SKB_FRAGS. When we try to
> linearize parts of the skb to let the rest of iov to be fit in
> the frags, we need count copylen into linear when calling tun_alloc_skb()
> instead of partly counting it into data_len. Since this breaks
> zerocopy_sg_from_iovec() since its inner counter assumes nr_frags should
> be zero at beginning. This cause nr_frags to be increased wrongly without
> setting the correct frags.
> 
> This bug were introduced from 0690899b4d4501b3505be069b9a687e68ccbe15b
> (tun: experimental zero copy tx support)
> 
> Cc: Michael S. Tsirkin 
> Signed-off-by: Jason Wang 


Acked-by: Michael S. Tsirkin 

> ---
> - This patch is needed for stable.
> - Changes from v1: introduce a local variable to track linear size
> ---
>  drivers/net/tun.c |9 ++---
>  1 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 9c61f87..c3cb60b 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1044,7 +1044,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, 
> struct tun_file *tfile,
>  {
>   struct tun_pi pi = { 0, cpu_to_be16(ETH_P_IP) };
>   struct sk_buff *skb;
> - size_t len = total_len, align = NET_SKB_PAD;
> + size_t len = total_len, align = NET_SKB_PAD, linear;
>   struct virtio_net_hdr gso = { 0 };
>   int offset = 0;
>   int copylen;
> @@ -1108,10 +1108,13 @@ static ssize_t tun_get_user(struct tun_struct *tun, 
> struct tun_file *tfile,
>   copylen = gso.hdr_len;
>   if (!copylen)
>   copylen = GOODCOPY_LEN;
> - } else
> + linear = copylen;
> + } else {
>   copylen = len;
> + linear = gso.hdr_len;
> + }
>  
> - skb = tun_alloc_skb(tfile, align, copylen, gso.hdr_len, noblock);
> + skb = tun_alloc_skb(tfile, align, copylen, linear, noblock);
>   if (IS_ERR(skb)) {
>   if (PTR_ERR(skb) != -EAGAIN)
>   tun->dev->stats.rx_dropped++;
> -- 
> 1.7.1
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Re: [PATCH v2 net 1/2] tuntap: correctly linearize skb when zerocopy is used

[Michael S. Tsirkin]

On Wed, Jul 10, 2013 at 01:43:27PM +0800, Jason Wang wrote:
 Userspace may produce vectors greater than MAX_SKB_FRAGS. When we try to
 linearize parts of the skb to let the rest of iov to be fit in
 the frags, we need count copylen into linear when calling tun_alloc_skb()
 instead of partly counting it into data_len. Since this breaks
 zerocopy_sg_from_iovec() since its inner counter assumes nr_frags should
 be zero at beginning. This cause nr_frags to be increased wrongly without
 setting the correct frags.
 
 This bug were introduced from 0690899b4d4501b3505be069b9a687e68ccbe15b
 (tun: experimental zero copy tx support)
 
 Cc: Michael S. Tsirkin m...@redhat.com
 Signed-off-by: Jason Wang jasow...@redhat.com


Acked-by: Michael S. Tsirkin m...@redhat.com

 ---
 - This patch is needed for stable.
 - Changes from v1: introduce a local variable to track linear size
 ---
  drivers/net/tun.c |9 ++---
  1 files changed, 6 insertions(+), 3 deletions(-)
 
 diff --git a/drivers/net/tun.c b/drivers/net/tun.c
 index 9c61f87..c3cb60b 100644
 --- a/drivers/net/tun.c
 +++ b/drivers/net/tun.c
 @@ -1044,7 +1044,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, 
 struct tun_file *tfile,
  {
   struct tun_pi pi = { 0, cpu_to_be16(ETH_P_IP) };
   struct sk_buff *skb;
 - size_t len = total_len, align = NET_SKB_PAD;
 + size_t len = total_len, align = NET_SKB_PAD, linear;
   struct virtio_net_hdr gso = { 0 };
   int offset = 0;
   int copylen;
 @@ -1108,10 +1108,13 @@ static ssize_t tun_get_user(struct tun_struct *tun, 
 struct tun_file *tfile,
   copylen = gso.hdr_len;
   if (!copylen)
   copylen = GOODCOPY_LEN;
 - } else
 + linear = copylen;
 + } else {
   copylen = len;
 + linear = gso.hdr_len;
 + }
  
 - skb = tun_alloc_skb(tfile, align, copylen, gso.hdr_len, noblock);
 + skb = tun_alloc_skb(tfile, align, copylen, linear, noblock);
   if (IS_ERR(skb)) {
   if (PTR_ERR(skb) != -EAGAIN)
   tun-dev-stats.rx_dropped++;
 -- 
 1.7.1
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[PATCH v2 net 1/2] tuntap: correctly linearize skb when zerocopy is used

[Jason Wang]

Userspace may produce vectors greater than MAX_SKB_FRAGS. When we try to
linearize parts of the skb to let the rest of iov to be fit in
the frags, we need count copylen into linear when calling tun_alloc_skb()
instead of partly counting it into data_len. Since this breaks
zerocopy_sg_from_iovec() since its inner counter assumes nr_frags should
be zero at beginning. This cause nr_frags to be increased wrongly without
setting the correct frags.

This bug were introduced from 0690899b4d4501b3505be069b9a687e68ccbe15b
(tun: experimental zero copy tx support)

Cc: Michael S. Tsirkin 
Signed-off-by: Jason Wang 
---
- This patch is needed for stable.
- Changes from v1: introduce a local variable to track linear size
---
 drivers/net/tun.c |9 ++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 9c61f87..c3cb60b 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1044,7 +1044,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, 
struct tun_file *tfile,
 {
struct tun_pi pi = { 0, cpu_to_be16(ETH_P_IP) };
struct sk_buff *skb;
-   size_t len = total_len, align = NET_SKB_PAD;
+   size_t len = total_len, align = NET_SKB_PAD, linear;
struct virtio_net_hdr gso = { 0 };
int offset = 0;
int copylen;
@@ -1108,10 +1108,13 @@ static ssize_t tun_get_user(struct tun_struct *tun, 
struct tun_file *tfile,
copylen = gso.hdr_len;
if (!copylen)
copylen = GOODCOPY_LEN;
-   } else
+   linear = copylen;
+   } else {
copylen = len;
+   linear = gso.hdr_len;
+   }
 
-   skb = tun_alloc_skb(tfile, align, copylen, gso.hdr_len, noblock);
+   skb = tun_alloc_skb(tfile, align, copylen, linear, noblock);
if (IS_ERR(skb)) {
if (PTR_ERR(skb) != -EAGAIN)
tun->dev->stats.rx_dropped++;
-- 
1.7.1

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[PATCH v2 net 1/2] tuntap: correctly linearize skb when zerocopy is used

[Jason Wang]

Userspace may produce vectors greater than MAX_SKB_FRAGS. When we try to
linearize parts of the skb to let the rest of iov to be fit in
the frags, we need count copylen into linear when calling tun_alloc_skb()
instead of partly counting it into data_len. Since this breaks
zerocopy_sg_from_iovec() since its inner counter assumes nr_frags should
be zero at beginning. This cause nr_frags to be increased wrongly without
setting the correct frags.

This bug were introduced from 0690899b4d4501b3505be069b9a687e68ccbe15b
(tun: experimental zero copy tx support)

Cc: Michael S. Tsirkin m...@redhat.com
Signed-off-by: Jason Wang jasow...@redhat.com
---
- This patch is needed for stable.
- Changes from v1: introduce a local variable to track linear size
---
 drivers/net/tun.c |9 ++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 9c61f87..c3cb60b 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1044,7 +1044,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, 
struct tun_file *tfile,
 {
struct tun_pi pi = { 0, cpu_to_be16(ETH_P_IP) };
struct sk_buff *skb;
-   size_t len = total_len, align = NET_SKB_PAD;
+   size_t len = total_len, align = NET_SKB_PAD, linear;
struct virtio_net_hdr gso = { 0 };
int offset = 0;
int copylen;
@@ -1108,10 +1108,13 @@ static ssize_t tun_get_user(struct tun_struct *tun, 
struct tun_file *tfile,
copylen = gso.hdr_len;
if (!copylen)
copylen = GOODCOPY_LEN;
-   } else
+   linear = copylen;
+   } else {
copylen = len;
+   linear = gso.hdr_len;
+   }
 
-   skb = tun_alloc_skb(tfile, align, copylen, gso.hdr_len, noblock);
+   skb = tun_alloc_skb(tfile, align, copylen, linear, noblock);
if (IS_ERR(skb)) {
if (PTR_ERR(skb) != -EAGAIN)
tun-dev-stats.rx_dropped++;
-- 
1.7.1

--
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Please read the FAQ at  http://www.tux.org/lkml/