[PATCH] net: fix fragments have the disallowed options

[PATCH] net: fix fragments have the disallowed options

[ooppublic]

From: caixf <ooppublic@163.com>

When in function ip_do_fragment() enter fsat path,
if skb have opthons, all fragments will have the same options.

Just guarantee the second fragment not have the disallowed options.

Signed-off-by: caixf <ooppublic@163.com>
---
 net/ipv4/ip_output.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 9bca57ef8b83..ce178b5eb848 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -826,15 +826,16 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 		/* Everything is OK. Generate! */
 		ip_fraglist_init(skb, iph, hlen, &iter);
 
-		if (iter.frag)
-			ip_options_fragment(iter.frag);
-
 		for (;;) {
 			/* Prepare header of the next frame,
 			 * before previous one went down. */
 			if (iter.frag) {
+				bool first_frag = (iter.offset == 0);
+
 				IPCB(iter.frag)->flags = IPCB(skb)->flags;
 				ip_fraglist_prepare(skb, &iter);
+				if (first_frag)
+					ip_options_fragment(iter.frag);
 			}
 
 			skb->tstamp = tstamp;
-- 
2.34.1

Re: [PATCH] net: fix fragments have the disallowed options

[Jakub Kicinski]

On Fri,  7 Jan 2022 16:05:59 +0800 ooppublic@163.com wrote:
> From: caixf <ooppublic@163.com>
> 
> When in function ip_do_fragment() enter fsat path,

fsat -> fast

> if skb have opthons, all fragments will have the same options.

opthons -> options

> Just guarantee the second fragment not have the disallowed options.

You're right. Can you send a patch which explicitly reverts these
two commits instead:

 1b9fbe813016b08e08b22ddba4ddbf9cb1b04b00
 faf482ca196a5b16007190529b3b2dd32ab3f761

I prefer the code the way it was before them, plus keeping the code how
it was could help backports.

Thanks!

Re: [PATCH] net: fix fragments have the disallowed options

[Jakub Kicinski]

On Fri,  7 Jan 2022 16:05:59 +0800 ooppublic@163.com wrote:
> From: caixf <ooppublic@163.com>
> 
> When in function ip_do_fragment() enter fsat path,
> if skb have opthons, all fragments will have the same options.
> 
> Just guarantee the second fragment not have the disallowed options.

#regzbot ^introduced: faf482ca196a5b16007190529b3b2dd32ab3f761

Re: [PATCH] net: fix fragments have the disallowed options

[Jakub Kicinski]

On Wed, 12 Jan 2022 10:43:24 -0800 Jakub Kicinski wrote:
> On Fri,  7 Jan 2022 16:05:59 +0800 ooppublic@163.com wrote:
> > From: caixf <ooppublic@163.com>
> > 
> > When in function ip_do_fragment() enter fsat path,  
> 
> fsat -> fast
> 
> > if skb have opthons, all fragments will have the same options.  
> 
> opthons -> options
> 
> > Just guarantee the second fragment not have the disallowed options.  
> 
> You're right. Can you send a patch which explicitly reverts these
> two commits instead:
> 
>  1b9fbe813016b08e08b22ddba4ddbf9cb1b04b00
>  faf482ca196a5b16007190529b3b2dd32ab3f761
> 
> I prefer the code the way it was before them, plus keeping the code how
> it was could help backports.

Please let us know if you're planning to send the new patch otherwise
I'll do the revert myself, it's a clear bug.