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From: Dan Carpenter <dan.carpenter@oracle.com>
To: yajun.deng@linux.dev
Cc: netdev@vger.kernel.org
Subject: [bug report] net: ipv4: Move ip_options_fragment() out of loop
Date: Fri, 27 Aug 2021 11:49:15 +0300	[thread overview]
Message-ID: <20210827084915.GA8737@kili> (raw)

Hello Yajun Deng,

This is a semi-automatic email about new static checker warnings.

The patch faf482ca196a: "net: ipv4: Move ip_options_fragment() out of 
loop" from Aug 23, 2021, leads to the following Smatch complaint:

    net/ipv4/ip_output.c:833 ip_do_fragment()
    warn: variable dereferenced before check 'iter.frag' (see line 828)

net/ipv4/ip_output.c
   827			ip_fraglist_init(skb, iph, hlen, &iter);
                                                         ^^^^^
iter.frag is set here.

   828			ip_options_fragment(iter.frag);
                                            ^^^^^^^^^
The patch introduces a new dereference here

   829	
   830			for (;;) {
   831				/* Prepare header of the next frame,
   832				 * before previous one went down. */
   833				if (iter.frag) {
                                    ^^^^^^^^^
But the old code assumed that "iter.frag" could be NULL.

   834					IPCB(iter.frag)->flags = IPCB(skb)->flags;
   835					ip_fraglist_prepare(skb, &iter);

regards,
dan carpenter

             reply	other threads:[~2021-08-27  8:49 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-27  8:49 Dan Carpenter [this message]
2021-08-27  9:23 ` [bug report] net: ipv4: Move ip_options_fragment() out of loop yajun.deng
2021-08-30  7:38   ` Dan Carpenter

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