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232 lines
9.4 KiB
Diff
232 lines
9.4 KiB
Diff
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From 2423496af35d94a87156b063ea5cedffc10a70a1 Mon Sep 17 00:00:00 2001
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From: Craig Gallek <kraig@google.com>
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Date: Tue, 16 May 2017 14:36:23 -0400
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Subject: ipv6: Prevent overrun when parsing v6 header options
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The KASAN warning repoted below was discovered with a syzkaller
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program. The reproducer is basically:
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int s = socket(AF_INET6, SOCK_RAW, NEXTHDR_HOP);
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send(s, &one_byte_of_data, 1, MSG_MORE);
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send(s, &more_than_mtu_bytes_data, 2000, 0);
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The socket() call sets the nexthdr field of the v6 header to
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NEXTHDR_HOP, the first send call primes the payload with a non zero
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byte of data, and the second send call triggers the fragmentation path.
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The fragmentation code tries to parse the header options in order
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to figure out where to insert the fragment option. Since nexthdr points
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to an invalid option, the calculation of the size of the network header
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can made to be much larger than the linear section of the skb and data
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is read outside of it.
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This fix makes ip6_find_1stfrag return an error if it detects
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running out-of-bounds.
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[ 42.361487] ==================================================================
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[ 42.364412] BUG: KASAN: slab-out-of-bounds in ip6_fragment+0x11c8/0x3730
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[ 42.365471] Read of size 840 at addr ffff88000969e798 by task ip6_fragment-oo/3789
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[ 42.366469]
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[ 42.366696] CPU: 1 PID: 3789 Comm: ip6_fragment-oo Not tainted 4.11.0+ #41
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[ 42.367628] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.1-1ubuntu1 04/01/2014
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[ 42.368824] Call Trace:
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[ 42.369183] dump_stack+0xb3/0x10b
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[ 42.369664] print_address_description+0x73/0x290
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[ 42.370325] kasan_report+0x252/0x370
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[ 42.370839] ? ip6_fragment+0x11c8/0x3730
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[ 42.371396] check_memory_region+0x13c/0x1a0
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[ 42.371978] memcpy+0x23/0x50
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[ 42.372395] ip6_fragment+0x11c8/0x3730
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[ 42.372920] ? nf_ct_expect_unregister_notifier+0x110/0x110
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[ 42.373681] ? ip6_copy_metadata+0x7f0/0x7f0
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[ 42.374263] ? ip6_forward+0x2e30/0x2e30
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[ 42.374803] ip6_finish_output+0x584/0x990
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[ 42.375350] ip6_output+0x1b7/0x690
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[ 42.375836] ? ip6_finish_output+0x990/0x990
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[ 42.376411] ? ip6_fragment+0x3730/0x3730
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[ 42.376968] ip6_local_out+0x95/0x160
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[ 42.377471] ip6_send_skb+0xa1/0x330
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[ 42.377969] ip6_push_pending_frames+0xb3/0xe0
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[ 42.378589] rawv6_sendmsg+0x2051/0x2db0
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[ 42.379129] ? rawv6_bind+0x8b0/0x8b0
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[ 42.379633] ? _copy_from_user+0x84/0xe0
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[ 42.380193] ? debug_check_no_locks_freed+0x290/0x290
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[ 42.380878] ? ___sys_sendmsg+0x162/0x930
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[ 42.381427] ? rcu_read_lock_sched_held+0xa3/0x120
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[ 42.382074] ? sock_has_perm+0x1f6/0x290
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[ 42.382614] ? ___sys_sendmsg+0x167/0x930
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[ 42.383173] ? lock_downgrade+0x660/0x660
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[ 42.383727] inet_sendmsg+0x123/0x500
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[ 42.384226] ? inet_sendmsg+0x123/0x500
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[ 42.384748] ? inet_recvmsg+0x540/0x540
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[ 42.385263] sock_sendmsg+0xca/0x110
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[ 42.385758] SYSC_sendto+0x217/0x380
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[ 42.386249] ? SYSC_connect+0x310/0x310
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[ 42.386783] ? __might_fault+0x110/0x1d0
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[ 42.387324] ? lock_downgrade+0x660/0x660
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[ 42.387880] ? __fget_light+0xa1/0x1f0
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[ 42.388403] ? __fdget+0x18/0x20
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[ 42.388851] ? sock_common_setsockopt+0x95/0xd0
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[ 42.389472] ? SyS_setsockopt+0x17f/0x260
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[ 42.390021] ? entry_SYSCALL_64_fastpath+0x5/0xbe
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[ 42.390650] SyS_sendto+0x40/0x50
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[ 42.391103] entry_SYSCALL_64_fastpath+0x1f/0xbe
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[ 42.391731] RIP: 0033:0x7fbbb711e383
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[ 42.392217] RSP: 002b:00007ffff4d34f28 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
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[ 42.393235] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fbbb711e383
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[ 42.394195] RDX: 0000000000001000 RSI: 00007ffff4d34f60 RDI: 0000000000000003
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[ 42.395145] RBP: 0000000000000046 R08: 00007ffff4d34f40 R09: 0000000000000018
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[ 42.396056] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000400aad
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[ 42.396598] R13: 0000000000000066 R14: 00007ffff4d34ee0 R15: 00007fbbb717af00
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[ 42.397257]
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[ 42.397411] Allocated by task 3789:
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[ 42.397702] save_stack_trace+0x16/0x20
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[ 42.398005] save_stack+0x46/0xd0
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[ 42.398267] kasan_kmalloc+0xad/0xe0
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[ 42.398548] kasan_slab_alloc+0x12/0x20
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[ 42.398848] __kmalloc_node_track_caller+0xcb/0x380
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[ 42.399224] __kmalloc_reserve.isra.32+0x41/0xe0
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[ 42.399654] __alloc_skb+0xf8/0x580
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[ 42.400003] sock_wmalloc+0xab/0xf0
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[ 42.400346] __ip6_append_data.isra.41+0x2472/0x33d0
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[ 42.400813] ip6_append_data+0x1a8/0x2f0
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[ 42.401122] rawv6_sendmsg+0x11ee/0x2db0
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[ 42.401505] inet_sendmsg+0x123/0x500
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[ 42.401860] sock_sendmsg+0xca/0x110
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[ 42.402209] ___sys_sendmsg+0x7cb/0x930
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[ 42.402582] __sys_sendmsg+0xd9/0x190
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[ 42.402941] SyS_sendmsg+0x2d/0x50
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[ 42.403273] entry_SYSCALL_64_fastpath+0x1f/0xbe
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[ 42.403718]
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[ 42.403871] Freed by task 1794:
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[ 42.404146] save_stack_trace+0x16/0x20
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[ 42.404515] save_stack+0x46/0xd0
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[ 42.404827] kasan_slab_free+0x72/0xc0
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[ 42.405167] kfree+0xe8/0x2b0
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[ 42.405462] skb_free_head+0x74/0xb0
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[ 42.405806] skb_release_data+0x30e/0x3a0
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[ 42.406198] skb_release_all+0x4a/0x60
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[ 42.406563] consume_skb+0x113/0x2e0
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[ 42.406910] skb_free_datagram+0x1a/0xe0
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[ 42.407288] netlink_recvmsg+0x60d/0xe40
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[ 42.407667] sock_recvmsg+0xd7/0x110
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[ 42.408022] ___sys_recvmsg+0x25c/0x580
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[ 42.408395] __sys_recvmsg+0xd6/0x190
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[ 42.408753] SyS_recvmsg+0x2d/0x50
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[ 42.409086] entry_SYSCALL_64_fastpath+0x1f/0xbe
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[ 42.409513]
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[ 42.409665] The buggy address belongs to the object at ffff88000969e780
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[ 42.409665] which belongs to the cache kmalloc-512 of size 512
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[ 42.410846] The buggy address is located 24 bytes inside of
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[ 42.410846] 512-byte region [ffff88000969e780, ffff88000969e980)
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[ 42.411941] The buggy address belongs to the page:
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[ 42.412405] page:ffffea000025a780 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0
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[ 42.413298] flags: 0x100000000008100(slab|head)
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[ 42.413729] raw: 0100000000008100 0000000000000000 0000000000000000 00000001800c000c
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[ 42.414387] raw: ffffea00002a9500 0000000900000007 ffff88000c401280 0000000000000000
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[ 42.415074] page dumped because: kasan: bad access detected
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[ 42.415604]
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[ 42.415757] Memory state around the buggy address:
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[ 42.416222] ffff88000969e880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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[ 42.416904] ffff88000969e900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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[ 42.417591] >ffff88000969e980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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[ 42.418273] ^
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[ 42.418588] ffff88000969ea00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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[ 42.419273] ffff88000969ea80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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[ 42.419882] ==================================================================
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Reported-by: Andrey Konovalov <andreyknvl@google.com>
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Signed-off-by: Craig Gallek <kraig@google.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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net/ipv6/ip6_offload.c | 2 ++
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net/ipv6/ip6_output.c | 4 ++++
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net/ipv6/output_core.c | 14 ++++++++------
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net/ipv6/udp_offload.c | 2 ++
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4 files changed, 16 insertions(+), 6 deletions(-)
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diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
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index 93e58a5..eab36ab 100644
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--- a/net/ipv6/ip6_offload.c
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+++ b/net/ipv6/ip6_offload.c
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@@ -117,6 +117,8 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
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if (udpfrag) {
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unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
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+ if (unfrag_ip6hlen < 0)
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+ return ERR_PTR(unfrag_ip6hlen);
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fptr = (struct frag_hdr *)((u8 *)ipv6h + unfrag_ip6hlen);
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fptr->frag_off = htons(offset);
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if (skb->next)
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diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
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index 58f6288..01deecd 100644
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--- a/net/ipv6/ip6_output.c
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+++ b/net/ipv6/ip6_output.c
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@@ -598,6 +598,10 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
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u8 *prevhdr, nexthdr = 0;
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hlen = ip6_find_1stfragopt(skb, &prevhdr);
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+ if (hlen < 0) {
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+ err = hlen;
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+ goto fail;
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+ }
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nexthdr = *prevhdr;
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mtu = ip6_skb_dst_mtu(skb);
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diff --git a/net/ipv6/output_core.c b/net/ipv6/output_core.c
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index cd42523..e9065b8 100644
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--- a/net/ipv6/output_core.c
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+++ b/net/ipv6/output_core.c
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@@ -79,14 +79,13 @@ EXPORT_SYMBOL(ipv6_select_ident);
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int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
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{
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u16 offset = sizeof(struct ipv6hdr);
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- struct ipv6_opt_hdr *exthdr =
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- (struct ipv6_opt_hdr *)(ipv6_hdr(skb) + 1);
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unsigned int packet_len = skb_tail_pointer(skb) -
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skb_network_header(skb);
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int found_rhdr = 0;
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*nexthdr = &ipv6_hdr(skb)->nexthdr;
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- while (offset + 1 <= packet_len) {
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+ while (offset <= packet_len) {
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+ struct ipv6_opt_hdr *exthdr;
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switch (**nexthdr) {
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@@ -107,13 +106,16 @@ int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
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return offset;
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}
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- offset += ipv6_optlen(exthdr);
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- *nexthdr = &exthdr->nexthdr;
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+ if (offset + sizeof(struct ipv6_opt_hdr) > packet_len)
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+ return -EINVAL;
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+
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exthdr = (struct ipv6_opt_hdr *)(skb_network_header(skb) +
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offset);
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+ offset += ipv6_optlen(exthdr);
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+ *nexthdr = &exthdr->nexthdr;
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}
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- return offset;
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+ return -EINVAL;
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}
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EXPORT_SYMBOL(ip6_find_1stfragopt);
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diff --git a/net/ipv6/udp_offload.c b/net/ipv6/udp_offload.c
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index ac858c4..b348cff 100644
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--- a/net/ipv6/udp_offload.c
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+++ b/net/ipv6/udp_offload.c
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@@ -91,6 +91,8 @@ static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
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* bytes to insert fragment header.
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*/
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unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
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+ if (unfrag_ip6hlen < 0)
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+ return ERR_PTR(unfrag_ip6hlen);
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nexthdr = *prevhdr;
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*prevhdr = NEXTHDR_FRAGMENT;
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unfrag_len = (skb_network_header(skb) - skb_mac_header(skb)) +
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--
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cgit v1.1
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