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TjVpfPhdNetMiYd/i2sO2b4= X-Google-Smtp-Source: ANB0VdbKXyUmmTl1rztqOtHgJ49+mcLkkbgL9dYR7Q+JJxqVVLHA+04mcxr2Iz/ax1o4h6MEX43DQw== X-Received: by 2002:a63:2701:: with SMTP id n1-v6mr3922043pgn.146.1536254840820; Thu, 06 Sep 2018 10:27:20 -0700 (PDT) Received: from ast-mbp.dhcp.thefacebook.com ([2620:10d:c090:200::5:7a4e]) by smtp.gmail.com with ESMTPSA id w81-v6sm12300838pfk.92.2018.09.06.10.27.19 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 06 Sep 2018 10:27:19 -0700 (PDT) Date: Thu, 6 Sep 2018 10:27:18 -0700 From: Alexei Starovoitov To: Eric Dumazet Cc: syzbot , ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net, dvyukov@google.com, herbert@gondor.apana.org.au, kuznet@ms2.inr.ac.ru, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, steffen.klassert@secunet.com, syzkaller-bugs@googlegroups.com, yoshfuji@linux-ipv6.org Subject: Re: KASAN: slab-out-of-bounds Read in _decode_session6 Message-ID: <20180906172713.cxjoazoo7asqggb3@ast-mbp.dhcp.thefacebook.com> References: <0000000000002bef6405752b530b@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: NeoMutt/20180223 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 06, 2018 at 12:00:26AM -0700, Eric Dumazet wrote: > > > On 09/05/2018 08:17 PM, syzbot wrote: > > syzbot has found a reproducer for the following crash on: > > > > HEAD commit:    b36fdc6853a3 Merge tag 'gpio-v4.19-2' of git://git.kernel... > > git tree:       upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=164938d1400000 > > kernel config:  https://syzkaller.appspot.com/x/.config?x=4c7e83258d6e0156 > > dashboard link: https://syzkaller.appspot.com/bug?extid=acffccec848dc13fe459 > > compiler:       gcc (GCC) 8.0.1 20180413 (experimental) > > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=115f172e400000 > > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16399be1400000 > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+acffccec848dc13fe459@syzkaller.appspotmail.com > > > > IPv6: ADDRCONF(NETDEV_UP): veth1: link is not ready > > IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready > > IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready > > 8021q: adding VLAN 0 to HW filter on device team0 > > ================================================================== > > BUG: KASAN: slab-out-of-bounds in _decode_session6+0x1331/0x14e0 net/ipv6/xfrm6_policy.c:161 > > Read of size 1 at addr ffff8801d4a67f07 by task syz-executor092/4673 > > > > CPU: 1 PID: 4673 Comm: syz-executor092 Not tainted 4.19.0-rc2+ #223 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > Call Trace: > >  __dump_stack lib/dump_stack.c:77 [inline] > >  dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113 > >  print_address_description+0x6c/0x20b mm/kasan/report.c:256 > >  kasan_report_error mm/kasan/report.c:354 [inline] > >  kasan_report.cold.7+0x242/0x30d mm/kasan/report.c:412 > >  __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430 > >  _decode_session6+0x1331/0x14e0 net/ipv6/xfrm6_policy.c:161 > >  __xfrm_decode_session+0x71/0x140 net/xfrm/xfrm_policy.c:2299 > >  xfrm_decode_session include/net/xfrm.h:1232 [inline] > >  vti6_tnl_xmit+0x3fc/0x1bb1 net/ipv6/ip6_vti.c:542 > >  __netdev_start_xmit include/linux/netdevice.h:4287 [inline] > >  netdev_start_xmit include/linux/netdevice.h:4296 [inline] > >  xmit_one net/core/dev.c:3216 [inline] > >  dev_hard_start_xmit+0x272/0xc10 net/core/dev.c:3232 > >  __dev_queue_xmit+0x2ab2/0x3870 net/core/dev.c:3802 > >  dev_queue_xmit+0x17/0x20 net/core/dev.c:3835 > >  __bpf_tx_skb net/core/filter.c:2012 [inline] > >  __bpf_redirect_common net/core/filter.c:2050 [inline] > >  __bpf_redirect+0x5b7/0xae0 net/core/filter.c:2057 > >  ____bpf_clone_redirect net/core/filter.c:2090 [inline] > >  bpf_clone_redirect+0x2f6/0x490 net/core/filter.c:2062 > >  bpf_prog_c39d1ba309a769f7+0xe9e/0x1000 > > > > Allocated by task 4673: > >  save_stack+0x43/0xd0 mm/kasan/kasan.c:448 > >  set_track mm/kasan/kasan.c:460 [inline] > >  kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553 > >  __do_kmalloc_node mm/slab.c:3682 [inline] > >  __kmalloc_node_track_caller+0x47/0x70 mm/slab.c:3696 > >  __kmalloc_reserve.isra.41+0x3a/0xe0 net/core/skbuff.c:137 > >  pskb_expand_head+0x230/0x10e0 net/core/skbuff.c:1463 > >  skb_ensure_writable+0x3dd/0x640 net/core/skbuff.c:5129 > >  __bpf_try_make_writable net/core/filter.c:1633 [inline] > >  bpf_try_make_writable net/core/filter.c:1639 [inline] > >  bpf_try_make_head_writable net/core/filter.c:1647 [inline] > >  ____bpf_clone_redirect net/core/filter.c:2084 [inline] > >  bpf_clone_redirect+0x14a/0x490 net/core/filter.c:2062 > >  bpf_prog_c39d1ba309a769f7+0xe9e/0x1000 > > > > Freed by task 3286: > >  save_stack+0x43/0xd0 mm/kasan/kasan.c:448 > >  set_track mm/kasan/kasan.c:460 [inline] > >  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521 > >  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 > >  __cache_free mm/slab.c:3498 [inline] > >  kfree+0xd9/0x210 mm/slab.c:3813 > >  load_elf_binary+0x2569/0x5610 fs/binfmt_elf.c:1118 > >  search_binary_handler+0x17d/0x570 fs/exec.c:1653 > >  exec_binprm fs/exec.c:1695 [inline] > >  __do_execve_file.isra.35+0x15ff/0x2460 fs/exec.c:1819 > >  do_execveat_common fs/exec.c:1866 [inline] > >  do_execve fs/exec.c:1883 [inline] > >  __do_sys_execve fs/exec.c:1964 [inline] > >  __se_sys_execve fs/exec.c:1959 [inline] > >  __x64_sys_execve+0x8f/0xc0 fs/exec.c:1959 > >  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 > >  entry_SYSCALL_64_after_hwframe+0x49/0xbe > > > > The buggy address belongs to the object at ffff8801d4a67d00 > >  which belongs to the cache kmalloc-512 of size 512 > > The buggy address is located 7 bytes to the right of > >  512-byte region [ffff8801d4a67d00, ffff8801d4a67f00) > > The buggy address belongs to the page: > > page:ffffea00075299c0 count:1 mapcount:0 mapping:ffff8801dac00940 index:0x0 > > flags: 0x2fffc0000000100(slab) > > raw: 02fffc0000000100 ffffea0007529988 ffffea0007529a48 ffff8801dac00940 > > raw: 0000000000000000 ffff8801d4a67080 0000000100000006 0000000000000000 > > page dumped because: kasan: bad access detected > > > > Memory state around the buggy address: > >  ffff8801d4a67e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > >  ffff8801d4a67e80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > >> ffff8801d4a67f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > >                    ^ > >  ffff8801d4a67f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > >  ffff8801d4a68000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ================================================================== > > > > > What about : > > diff --git a/net/core/filter.c b/net/core/filter.c > index aecdeba052d3f0ff3d4f0a33ec36891f9738052c..a662f59786bd0677850c1c60a2c92faa6fb6c5bb 100644 > --- a/net/core/filter.c > +++ b/net/core/filter.c > @@ -2081,7 +2081,7 @@ BPF_CALL_3(bpf_clone_redirect, struct sk_buff *, skb, u32, ifindex, u64, flags) > * here, we need to free the just generated clone to unclone once > * again. > */ > - ret = bpf_try_make_head_writable(skb); > + ret = bpf_try_make_head_writable(clone); This part is fine. I think the bug is in _decode_session6, but I have a hard time reproducing the issue, so will appreciate if somebody can test the following patch: >From 291f80f212461670d1e0140d06eee3071cf3e1ee Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Thu, 6 Sep 2018 10:23:29 -0700 Subject: [PATCH] net/xfrm: fix out-of-bounds packet access BUG: KASAN: slab-out-of-bounds in _decode_session6+0x1331/0x14e0 net/ipv6/xfrm6_policy.c:161 Read of size 1 at addr ffff8801d882eec7 by task syz-executor1/6667 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113 print_address_description+0x6c/0x20b mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report.cold.7+0x242/0x30d mm/kasan/report.c:412 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430 _decode_session6+0x1331/0x14e0 net/ipv6/xfrm6_policy.c:161 __xfrm_decode_session+0x71/0x140 net/xfrm/xfrm_policy.c:2299 xfrm_decode_session include/net/xfrm.h:1232 [inline] vti6_tnl_xmit+0x3c3/0x1bc1 net/ipv6/ip6_vti.c:542 __netdev_start_xmit include/linux/netdevice.h:4313 [inline] netdev_start_xmit include/linux/netdevice.h:4322 [inline] xmit_one net/core/dev.c:3217 [inline] dev_hard_start_xmit+0x272/0xc10 net/core/dev.c:3233 __dev_queue_xmit+0x2ab2/0x3870 net/core/dev.c:3803 dev_queue_xmit+0x17/0x20 net/core/dev.c:3836 Reported-by: syzbot+acffccec848dc13fe459@syzkaller.appspotmail.com Signed-off-by: Alexei Starovoitov --- net/ipv6/xfrm6_policy.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv6/xfrm6_policy.c b/net/ipv6/xfrm6_policy.c index ef3defaf43b9..d35bcf92969c 100644 --- a/net/ipv6/xfrm6_policy.c +++ b/net/ipv6/xfrm6_policy.c @@ -146,8 +146,8 @@ _decode_session6(struct sk_buff *skb, struct flowi *fl, int reverse) fl6->daddr = reverse ? hdr->saddr : hdr->daddr; fl6->saddr = reverse ? hdr->daddr : hdr->saddr; - while (nh + offset + 1 < skb->data || - pskb_may_pull(skb, nh + offset + 1 - skb->data)) { + while (nh + offset + sizeof(*exthdr) < skb->data || + pskb_may_pull(skb, nh + offset + sizeof(*exthdr) - skb->data)) { nh = skb_network_header(skb); exthdr = (struct ipv6_opt_hdr *)(nh + offset); -- 2.17.1 From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexei Starovoitov Subject: Re: KASAN: slab-out-of-bounds Read in _decode_session6 Date: Thu, 6 Sep 2018 10:27:18 -0700 Message-ID: <20180906172713.cxjoazoo7asqggb3@ast-mbp.dhcp.thefacebook.com> References: <0000000000002bef6405752b530b@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Cc: syzbot , ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net, dvyukov@google.com, herbert@gondor.apana.org.au, kuznet@ms2.inr.ac.ru, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, steffen.klassert@secunet.com, syzkaller-bugs@googlegroups.com, yoshfuji@linux-ipv6.org To: Eric Dumazet Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Thu, Sep 06, 2018 at 12:00:26AM -0700, Eric Dumazet wrote: > > > On 09/05/2018 08:17 PM, syzbot wrote: > > syzbot has found a reproducer for the following crash on: > > > > HEAD commit:    b36fdc6853a3 Merge tag 'gpio-v4.19-2' of git://git.kernel... > > git tree:       upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=164938d1400000 > > kernel config:  https://syzkaller.appspot.com/x/.config?x=4c7e83258d6e0156 > > dashboard link: https://syzkaller.appspot.com/bug?extid=acffccec848dc13fe459 > > compiler:       gcc (GCC) 8.0.1 20180413 (experimental) > > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=115f172e400000 > > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16399be1400000 > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+acffccec848dc13fe459@syzkaller.appspotmail.com > > > > IPv6: ADDRCONF(NETDEV_UP): veth1: link is not ready > > IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready > > IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready > > 8021q: adding VLAN 0 to HW filter on device team0 > > ================================================================== > > BUG: KASAN: slab-out-of-bounds in _decode_session6+0x1331/0x14e0 net/ipv6/xfrm6_policy.c:161 > > Read of size 1 at addr ffff8801d4a67f07 by task syz-executor092/4673 > > > > CPU: 1 PID: 4673 Comm: syz-executor092 Not tainted 4.19.0-rc2+ #223 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > Call Trace: > >  __dump_stack lib/dump_stack.c:77 [inline] > >  dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113 > >  print_address_description+0x6c/0x20b mm/kasan/report.c:256 > >  kasan_report_error mm/kasan/report.c:354 [inline] > >  kasan_report.cold.7+0x242/0x30d mm/kasan/report.c:412 > >  __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430 > >  _decode_session6+0x1331/0x14e0 net/ipv6/xfrm6_policy.c:161 > >  __xfrm_decode_session+0x71/0x140 net/xfrm/xfrm_policy.c:2299 > >  xfrm_decode_session include/net/xfrm.h:1232 [inline] > >  vti6_tnl_xmit+0x3fc/0x1bb1 net/ipv6/ip6_vti.c:542 > >  __netdev_start_xmit include/linux/netdevice.h:4287 [inline] > >  netdev_start_xmit include/linux/netdevice.h:4296 [inline] > >  xmit_one net/core/dev.c:3216 [inline] > >  dev_hard_start_xmit+0x272/0xc10 net/core/dev.c:3232 > >  __dev_queue_xmit+0x2ab2/0x3870 net/core/dev.c:3802 > >  dev_queue_xmit+0x17/0x20 net/core/dev.c:3835 > >  __bpf_tx_skb net/core/filter.c:2012 [inline] > >  __bpf_redirect_common net/core/filter.c:2050 [inline] > >  __bpf_redirect+0x5b7/0xae0 net/core/filter.c:2057 > >  ____bpf_clone_redirect net/core/filter.c:2090 [inline] > >  bpf_clone_redirect+0x2f6/0x490 net/core/filter.c:2062 > >  bpf_prog_c39d1ba309a769f7+0xe9e/0x1000 > > > > Allocated by task 4673: > >  save_stack+0x43/0xd0 mm/kasan/kasan.c:448 > >  set_track mm/kasan/kasan.c:460 [inline] > >  kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553 > >  __do_kmalloc_node mm/slab.c:3682 [inline] > >  __kmalloc_node_track_caller+0x47/0x70 mm/slab.c:3696 > >  __kmalloc_reserve.isra.41+0x3a/0xe0 net/core/skbuff.c:137 > >  pskb_expand_head+0x230/0x10e0 net/core/skbuff.c:1463 > >  skb_ensure_writable+0x3dd/0x640 net/core/skbuff.c:5129 > >  __bpf_try_make_writable net/core/filter.c:1633 [inline] > >  bpf_try_make_writable net/core/filter.c:1639 [inline] > >  bpf_try_make_head_writable net/core/filter.c:1647 [inline] > >  ____bpf_clone_redirect net/core/filter.c:2084 [inline] > >  bpf_clone_redirect+0x14a/0x490 net/core/filter.c:2062 > >  bpf_prog_c39d1ba309a769f7+0xe9e/0x1000 > > > > Freed by task 3286: > >  save_stack+0x43/0xd0 mm/kasan/kasan.c:448 > >  set_track mm/kasan/kasan.c:460 [inline] > >  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521 > >  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 > >  __cache_free mm/slab.c:3498 [inline] > >  kfree+0xd9/0x210 mm/slab.c:3813 > >  load_elf_binary+0x2569/0x5610 fs/binfmt_elf.c:1118 > >  search_binary_handler+0x17d/0x570 fs/exec.c:1653 > >  exec_binprm fs/exec.c:1695 [inline] > >  __do_execve_file.isra.35+0x15ff/0x2460 fs/exec.c:1819 > >  do_execveat_common fs/exec.c:1866 [inline] > >  do_execve fs/exec.c:1883 [inline] > >  __do_sys_execve fs/exec.c:1964 [inline] > >  __se_sys_execve fs/exec.c:1959 [inline] > >  __x64_sys_execve+0x8f/0xc0 fs/exec.c:1959 > >  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 > >  entry_SYSCALL_64_after_hwframe+0x49/0xbe > > > > The buggy address belongs to the object at ffff8801d4a67d00 > >  which belongs to the cache kmalloc-512 of size 512 > > The buggy address is located 7 bytes to the right of > >  512-byte region [ffff8801d4a67d00, ffff8801d4a67f00) > > The buggy address belongs to the page: > > page:ffffea00075299c0 count:1 mapcount:0 mapping:ffff8801dac00940 index:0x0 > > flags: 0x2fffc0000000100(slab) > > raw: 02fffc0000000100 ffffea0007529988 ffffea0007529a48 ffff8801dac00940 > > raw: 0000000000000000 ffff8801d4a67080 0000000100000006 0000000000000000 > > page dumped because: kasan: bad access detected > > > > Memory state around the buggy address: > >  ffff8801d4a67e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > >  ffff8801d4a67e80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > >> ffff8801d4a67f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > >                    ^ > >  ffff8801d4a67f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > >  ffff8801d4a68000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ================================================================== > > > > > What about : > > diff --git a/net/core/filter.c b/net/core/filter.c > index aecdeba052d3f0ff3d4f0a33ec36891f9738052c..a662f59786bd0677850c1c60a2c92faa6fb6c5bb 100644 > --- a/net/core/filter.c > +++ b/net/core/filter.c > @@ -2081,7 +2081,7 @@ BPF_CALL_3(bpf_clone_redirect, struct sk_buff *, skb, u32, ifindex, u64, flags) > * here, we need to free the just generated clone to unclone once > * again. > */ > - ret = bpf_try_make_head_writable(skb); > + ret = bpf_try_make_head_writable(clone); This part is fine. I think the bug is in _decode_session6, but I have a hard time reproducing the issue, so will appreciate if somebody can test the following patch: >>From 291f80f212461670d1e0140d06eee3071cf3e1ee Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Thu, 6 Sep 2018 10:23:29 -0700 Subject: [PATCH] net/xfrm: fix out-of-bounds packet access BUG: KASAN: slab-out-of-bounds in _decode_session6+0x1331/0x14e0 net/ipv6/xfrm6_policy.c:161 Read of size 1 at addr ffff8801d882eec7 by task syz-executor1/6667 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113 print_address_description+0x6c/0x20b mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report.cold.7+0x242/0x30d mm/kasan/report.c:412 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430 _decode_session6+0x1331/0x14e0 net/ipv6/xfrm6_policy.c:161 __xfrm_decode_session+0x71/0x140 net/xfrm/xfrm_policy.c:2299 xfrm_decode_session include/net/xfrm.h:1232 [inline] vti6_tnl_xmit+0x3c3/0x1bc1 net/ipv6/ip6_vti.c:542 __netdev_start_xmit include/linux/netdevice.h:4313 [inline] netdev_start_xmit include/linux/netdevice.h:4322 [inline] xmit_one net/core/dev.c:3217 [inline] dev_hard_start_xmit+0x272/0xc10 net/core/dev.c:3233 __dev_queue_xmit+0x2ab2/0x3870 net/core/dev.c:3803 dev_queue_xmit+0x17/0x20 net/core/dev.c:3836 Reported-by: syzbot+acffccec848dc13fe459@syzkaller.appspotmail.com Signed-off-by: Alexei Starovoitov --- net/ipv6/xfrm6_policy.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv6/xfrm6_policy.c b/net/ipv6/xfrm6_policy.c index ef3defaf43b9..d35bcf92969c 100644 --- a/net/ipv6/xfrm6_policy.c +++ b/net/ipv6/xfrm6_policy.c @@ -146,8 +146,8 @@ _decode_session6(struct sk_buff *skb, struct flowi *fl, int reverse) fl6->daddr = reverse ? hdr->saddr : hdr->daddr; fl6->saddr = reverse ? hdr->daddr : hdr->saddr; - while (nh + offset + 1 < skb->data || - pskb_may_pull(skb, nh + offset + 1 - skb->data)) { + while (nh + offset + sizeof(*exthdr) < skb->data || + pskb_may_pull(skb, nh + offset + sizeof(*exthdr) - skb->data)) { nh = skb_network_header(skb); exthdr = (struct ipv6_opt_hdr *)(nh + offset); -- 2.17.1