[PATCH stable 3.10-3.16] tcp: Fix crash in TCP Fast Open

[PATCH stable 3.10-3.16] tcp: Fix crash in TCP Fast Open

[Ben Hutchings]

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Commit 355a901e6cf1 ("tcp: make connect() mem charging friendly")
changed tcp_send_syn_data() to perform an open-coded copy of the 'syn'
skb rather than using skb_copy_expand().

The open-coded copy does not cover the skb_shared_info::gso_segs
field, so in the new skb it is left set to 0.  When this commit was
backported into stable branches between 3.10.y and 3.16.7-ckty
inclusive, it triggered the BUG() in tcp_transmit_skb().

Since Linux 3.18 the GSO segment count is kept in the
tcp_skb_cb::tcp_gso_segs field and tcp_send_syn_data() does copy the
tcp_skb_cb structure to the new skb, so mainline and newer stable
branches are not affected.

Set skb_shared_info::gso_segs to the correct value of 1.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 net/ipv4/tcp_output.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index d5457e4..1ea0a07 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2992,6 +2992,7 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
 		goto fallback;
 	syn_data->ip_summed = CHECKSUM_PARTIAL;
 	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
+	skb_shinfo(syn_data)->gso_segs = 1;
 	if (unlikely(memcpy_fromiovecend(skb_put(syn_data, space),
 					 fo->data->msg_iov, 0, space))) {
 		kfree_skb(syn_data);

-- 
Ben Hutchings
Editing code like this is akin to sticking plasters on the bleeding stump
of a severed limb. - me, 29 June 1999

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Re: [PATCH stable 3.10-3.16] tcp: Fix crash in TCP Fast Open

[Eric Dumazet]

On Wed, 2015-04-15 at 19:00 +0100, Ben Hutchings wrote:
> Commit 355a901e6cf1 ("tcp: make connect() mem charging friendly")
> changed tcp_send_syn_data() to perform an open-coded copy of the 'syn'
> skb rather than using skb_copy_expand().
> 
> The open-coded copy does not cover the skb_shared_info::gso_segs
> field, so in the new skb it is left set to 0.  When this commit was
> backported into stable branches between 3.10.y and 3.16.7-ckty
> inclusive, it triggered the BUG() in tcp_transmit_skb().
> 
> Since Linux 3.18 the GSO segment count is kept in the
> tcp_skb_cb::tcp_gso_segs field and tcp_send_syn_data() does copy the
> tcp_skb_cb structure to the new skb, so mainline and newer stable
> branches are not affected.
> 
> Set skb_shared_info::gso_segs to the correct value of 1.
> 
> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> ---
>  net/ipv4/tcp_output.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index d5457e4..1ea0a07 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -2992,6 +2992,7 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
>  		goto fallback;
>  	syn_data->ip_summed = CHECKSUM_PARTIAL;
>  	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
> +	skb_shinfo(syn_data)->gso_segs = 1;
>  	if (unlikely(memcpy_fromiovecend(skb_put(syn_data, space),
>  					 fo->data->msg_iov, 0, space))) {
>  		kfree_skb(syn_data);
> 

Looks goot to me, thanks Ben !

Acked-by: Eric Dumazet <edumazet@google.com>

Re: [PATCH stable 3.10-3.16] tcp: Fix crash in TCP Fast Open

[David Miller]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Wed, 15 Apr 2015 11:22:44 -0700

> On Wed, 2015-04-15 at 19:00 +0100, Ben Hutchings wrote:
>> Commit 355a901e6cf1 ("tcp: make connect() mem charging friendly")
>> changed tcp_send_syn_data() to perform an open-coded copy of the 'syn'
>> skb rather than using skb_copy_expand().
>> 
>> The open-coded copy does not cover the skb_shared_info::gso_segs
>> field, so in the new skb it is left set to 0.  When this commit was
>> backported into stable branches between 3.10.y and 3.16.7-ckty
>> inclusive, it triggered the BUG() in tcp_transmit_skb().
>> 
>> Since Linux 3.18 the GSO segment count is kept in the
>> tcp_skb_cb::tcp_gso_segs field and tcp_send_syn_data() does copy the
>> tcp_skb_cb structure to the new skb, so mainline and newer stable
>> branches are not affected.
>> 
>> Set skb_shared_info::gso_segs to the correct value of 1.
>> 
>> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
 ...
> Looks goot to me, thanks Ben !
> 
> Acked-by: Eric Dumazet <edumazet@google.com>

Ben, thanks for taking care of this.

Re: [PATCH stable 3.10-3.16] tcp: Fix crash in TCP Fast Open

[Luis Henriques]

On Wed, Apr 15, 2015 at 07:00:32PM +0100, Ben Hutchings wrote:
> Commit 355a901e6cf1 ("tcp: make connect() mem charging friendly")
> changed tcp_send_syn_data() to perform an open-coded copy of the 'syn'
> skb rather than using skb_copy_expand().
> 
> The open-coded copy does not cover the skb_shared_info::gso_segs
> field, so in the new skb it is left set to 0.  When this commit was
> backported into stable branches between 3.10.y and 3.16.7-ckty
> inclusive, it triggered the BUG() in tcp_transmit_skb().
> 
> Since Linux 3.18 the GSO segment count is kept in the
> tcp_skb_cb::tcp_gso_segs field and tcp_send_syn_data() does copy the
> tcp_skb_cb structure to the new skb, so mainline and newer stable
> branches are not affected.
> 
> Set skb_shared_info::gso_segs to the correct value of 1.
> 
> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

Thanks a lot, Ben.  I'll queue this for the next 3.16 kernel release.

Cheers,
--
Luís

> ---
>  net/ipv4/tcp_output.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index d5457e4..1ea0a07 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -2992,6 +2992,7 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
>  		goto fallback;
>  	syn_data->ip_summed = CHECKSUM_PARTIAL;
>  	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
> +	skb_shinfo(syn_data)->gso_segs = 1;
>  	if (unlikely(memcpy_fromiovecend(skb_put(syn_data, space),
>  					 fo->data->msg_iov, 0, space))) {
>  		kfree_skb(syn_data);
> 
> -- 
> Ben Hutchings
> Editing code like this is akin to sticking plasters on the bleeding stump
> of a severed limb. - me, 29 June 1999

Re: [PATCH stable 3.10-3.16] tcp: Fix crash in TCP Fast Open

[Greg KH]

On Wed, Apr 15, 2015 at 07:00:32PM +0100, Ben Hutchings wrote:
> Commit 355a901e6cf1 ("tcp: make connect() mem charging friendly")
> changed tcp_send_syn_data() to perform an open-coded copy of the 'syn'
> skb rather than using skb_copy_expand().
> 
> The open-coded copy does not cover the skb_shared_info::gso_segs
> field, so in the new skb it is left set to 0.  When this commit was
> backported into stable branches between 3.10.y and 3.16.7-ckty
> inclusive, it triggered the BUG() in tcp_transmit_skb().
> 
> Since Linux 3.18 the GSO segment count is kept in the
> tcp_skb_cb::tcp_gso_segs field and tcp_send_syn_data() does copy the
> tcp_skb_cb structure to the new skb, so mainline and newer stable
> branches are not affected.
> 
> Set skb_shared_info::gso_segs to the correct value of 1.
> 
> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> ---
>  net/ipv4/tcp_output.c | 1 +
>  1 file changed, 1 insertion(+)

Thanks for working on this and sending the patch out.

greg k-h

Patch "tcp: Fix crash in TCP Fast Open" has been added to the 3.10-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    tcp: Fix crash in TCP Fast Open

to the 3.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tcp-fix-crash-in-tcp-fast-open.patch
and it can be found in the queue-3.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From ben@decadent.org.uk  Fri Apr 17 11:41:49 2015
From: Ben Hutchings <ben@decadent.org.uk>
Date: Wed, 15 Apr 2015 19:00:32 +0100
Subject: tcp: Fix crash in TCP Fast Open
To: stable <stable@vger.kernel.org>
Cc: netdev <netdev@vger.kernel.org>, Eric Dumazet <eric.dumazet@gmail.com>, 782515@bugs.debian.org
Message-ID: <1429120832.3211.91.camel@decadent.org.uk>

From: Ben Hutchings <ben@decadent.org.uk>

Commit 355a901e6cf1 ("tcp: make connect() mem charging friendly")
changed tcp_send_syn_data() to perform an open-coded copy of the 'syn'
skb rather than using skb_copy_expand().

The open-coded copy does not cover the skb_shared_info::gso_segs
field, so in the new skb it is left set to 0.  When this commit was
backported into stable branches between 3.10.y and 3.16.7-ckty
inclusive, it triggered the BUG() in tcp_transmit_skb().

Since Linux 3.18 the GSO segment count is kept in the
tcp_skb_cb::tcp_gso_segs field and tcp_send_syn_data() does copy the
tcp_skb_cb structure to the new skb, so mainline and newer stable
branches are not affected.

Set skb_shared_info::gso_segs to the correct value of 1.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/ipv4/tcp_output.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2909,6 +2909,7 @@ static int tcp_send_syn_data(struct sock
 		goto fallback;
 	syn_data->ip_summed = CHECKSUM_PARTIAL;
 	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
+	skb_shinfo(syn_data)->gso_segs = 1;
 	if (unlikely(memcpy_fromiovecend(skb_put(syn_data, space),
 					 fo->data->msg_iov, 0, space))) {
 		kfree_skb(syn_data);


Patches currently in stable-queue which might be from ben@decadent.org.uk are

queue-3.10/tcp-fix-crash-in-tcp-fast-open.patch

Patch "tcp: Fix crash in TCP Fast Open" has been added to the 3.14-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    tcp: Fix crash in TCP Fast Open

to the 3.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tcp-fix-crash-in-tcp-fast-open.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From ben@decadent.org.uk  Fri Apr 17 11:41:49 2015
From: Ben Hutchings <ben@decadent.org.uk>
Date: Wed, 15 Apr 2015 19:00:32 +0100
Subject: tcp: Fix crash in TCP Fast Open
To: stable <stable@vger.kernel.org>
Cc: netdev <netdev@vger.kernel.org>, Eric Dumazet <eric.dumazet@gmail.com>, 782515@bugs.debian.org
Message-ID: <1429120832.3211.91.camel@decadent.org.uk>

From: Ben Hutchings <ben@decadent.org.uk>

Commit 355a901e6cf1 ("tcp: make connect() mem charging friendly")
changed tcp_send_syn_data() to perform an open-coded copy of the 'syn'
skb rather than using skb_copy_expand().

The open-coded copy does not cover the skb_shared_info::gso_segs
field, so in the new skb it is left set to 0.  When this commit was
backported into stable branches between 3.10.y and 3.16.7-ckty
inclusive, it triggered the BUG() in tcp_transmit_skb().

Since Linux 3.18 the GSO segment count is kept in the
tcp_skb_cb::tcp_gso_segs field and tcp_send_syn_data() does copy the
tcp_skb_cb structure to the new skb, so mainline and newer stable
branches are not affected.

Set skb_shared_info::gso_segs to the correct value of 1.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/ipv4/tcp_output.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2933,6 +2933,7 @@ static int tcp_send_syn_data(struct sock
 		goto fallback;
 	syn_data->ip_summed = CHECKSUM_PARTIAL;
 	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
+	skb_shinfo(syn_data)->gso_segs = 1;
 	if (unlikely(memcpy_fromiovecend(skb_put(syn_data, space),
 					 fo->data->msg_iov, 0, space))) {
 		kfree_skb(syn_data);


Patches currently in stable-queue which might be from ben@decadent.org.uk are

queue-3.14/tcp-fix-crash-in-tcp-fast-open.patch

Re: [PATCH stable 3.10-3.16] tcp: Fix crash in TCP Fast Open

[Kamal Mostafa]

On Wed, 2015-04-15 at 19:00 +0100, Ben Hutchings wrote:
> Commit 355a901e6cf1 ("tcp: make connect() mem charging friendly")
> changed tcp_send_syn_data() to perform an open-coded copy of the 'syn'
> skb rather than using skb_copy_expand().
> 
> The open-coded copy does not cover the skb_shared_info::gso_segs
> field, so in the new skb it is left set to 0.  When this commit was
> backported into stable branches between 3.10.y and 3.16.7-ckty
> inclusive, it triggered the BUG() in tcp_transmit_skb().
> 
> Since Linux 3.18 the GSO segment count is kept in the
> tcp_skb_cb::tcp_gso_segs field and tcp_send_syn_data() does copy the
> tcp_skb_cb structure to the new skb, so mainline and newer stable
> branches are not affected.
> 
> Set skb_shared_info::gso_segs to the correct value of 1.
> 
> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>


Queued for 3.13-stable.  Thanks very much, Ben!

 -Kamal


> ---
>  net/ipv4/tcp_output.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index d5457e4..1ea0a07 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -2992,6 +2992,7 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
>  		goto fallback;
>  	syn_data->ip_summed = CHECKSUM_PARTIAL;
>  	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
> +	skb_shinfo(syn_data)->gso_segs = 1;
>  	if (unlikely(memcpy_fromiovecend(skb_put(syn_data, space),
>  					 fo->data->msg_iov, 0, space))) {
>  		kfree_skb(syn_data);
>