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Message-ID: <20250711182139.3580864-1-kuniyu@google.com>
Date: Fri, 11 Jul 2025 18:21:19 +0000
From: Kuniyuki Iwashima <kuniyu@...gle.com>
To: "David S. Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, Alexander Aring <alex.aring@...il.com>,
Kuniyuki Iwashima <kuniyu@...gle.com>, Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org
Subject: [PATCH v1 net] rpl: Fix use-after-free in rpl_do_srh_inline().
Running lwt_dst_cache_ref_loop.sh in selftest with KASAN triggers
the splat below [0].
rpl_do_srh_inline() fetches ipv6_hdr(skb) and accesses it after
skb_cow_head(), which is illegal as the header could be freed then.
Let's fix it by making oldhdr to a local struct instead of a pointer.
[0]:
[root@...ora net]# ./lwt_dst_cache_ref_loop.sh
...
TEST: rpl (input)
[ 57.631529] ==================================================================
BUG: KASAN: slab-use-after-free in rpl_do_srh_inline.isra.0 (net/ipv6/rpl_iptunnel.c:174)
Read of size 40 at addr ffff888122bf96d8 by task ping6/1543
CPU: 50 UID: 0 PID: 1543 Comm: ping6 Not tainted 6.16.0-rc5-01302-gfadd1e6231b1 #23 PREEMPT(voluntary)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<IRQ>
dump_stack_lvl (lib/dump_stack.c:122)
print_report (mm/kasan/report.c:409 mm/kasan/report.c:521)
kasan_report (mm/kasan/report.c:221 mm/kasan/report.c:636)
kasan_check_range (mm/kasan/generic.c:175 (discriminator 1) mm/kasan/generic.c:189 (discriminator 1))
__asan_memmove (mm/kasan/shadow.c:94 (discriminator 2))
rpl_do_srh_inline.isra.0 (net/ipv6/rpl_iptunnel.c:174)
rpl_input (net/ipv6/rpl_iptunnel.c:201 net/ipv6/rpl_iptunnel.c:282)
lwtunnel_input (net/core/lwtunnel.c:459)
ipv6_rcv (./include/net/dst.h:471 (discriminator 1) ./include/net/dst.h:469 (discriminator 1) net/ipv6/ip6_input.c:79 (discriminator 1) ./include/linux/netfilter.h:317 (discriminator 1) ./include/linux/netfilter.h:311 (discriminator 1) net/ipv6/ip6_input.c:311 (discriminator 1))
__netif_receive_skb_one_core (net/core/dev.c:5967)
process_backlog (./include/linux/rcupdate.h:869 net/core/dev.c:6440)
__napi_poll.constprop.0 (net/core/dev.c:7452)
net_rx_action (net/core/dev.c:7518 net/core/dev.c:7643)
handle_softirqs (kernel/softirq.c:579)
do_softirq (kernel/softirq.c:480 (discriminator 20))
</IRQ>
<TASK>
__local_bh_enable_ip (kernel/softirq.c:407)
__dev_queue_xmit (net/core/dev.c:4740)
ip6_finish_output2 (./include/linux/netdevice.h:3358 ./include/net/neighbour.h:526 ./include/net/neighbour.h:540 net/ipv6/ip6_output.c:141)
ip6_finish_output (net/ipv6/ip6_output.c:215 net/ipv6/ip6_output.c:226)
ip6_output (./include/linux/netfilter.h:306 net/ipv6/ip6_output.c:248)
ip6_send_skb (net/ipv6/ip6_output.c:1983)
rawv6_sendmsg (net/ipv6/raw.c:588 net/ipv6/raw.c:918)
__sys_sendto (net/socket.c:714 (discriminator 1) net/socket.c:729 (discriminator 1) net/socket.c:2228 (discriminator 1))
__x64_sys_sendto (net/socket.c:2231)
do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1))
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
RIP: 0033:0x7f68cffb2a06
Code: 5d e8 41 8b 93 08 03 00 00 59 5e 48 83 f8 fc 75 19 83 e2 39 83 fa 08 75 11 e8 26 ff ff ff 66 0f 1f 44 00 00 48 8b 45 10 0f 05 <48> 8b 5d f8 c9 c3 0f 1f 40 00 f3 0f 1e fa 55 48 89 e5 48 83 ec 08
RSP: 002b:00007ffefb7c53d0 EFLAGS: 00000202 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000564cd69f10a0 RCX: 00007f68cffb2a06
RDX: 0000000000000040 RSI: 0000564cd69f10a4 RDI: 0000000000000003
RBP: 00007ffefb7c53f0 R08: 0000564cd6a032ac R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000202 R12: 0000564cd69f10a4
R13: 0000000000000040 R14: 00007ffefb7c66e0 R15: 0000564cd69f10a0
</TASK>
Allocated by task 1543:
kasan_save_stack (mm/kasan/common.c:48)
kasan_save_track (mm/kasan/common.c:60 (discriminator 1) mm/kasan/common.c:69 (discriminator 1))
__kasan_slab_alloc (mm/kasan/common.c:319 mm/kasan/common.c:345)
kmem_cache_alloc_node_noprof (./include/linux/kasan.h:250 mm/slub.c:4148 mm/slub.c:4197 mm/slub.c:4249)
kmalloc_reserve (net/core/skbuff.c:581 (discriminator 88))
__alloc_skb (net/core/skbuff.c:669)
__ip6_append_data (net/ipv6/ip6_output.c:1672 (discriminator 1))
ip6_append_data (net/ipv6/ip6_output.c:1859)
rawv6_sendmsg (net/ipv6/raw.c:911)
__sys_sendto (net/socket.c:714 (discriminator 1) net/socket.c:729 (discriminator 1) net/socket.c:2228 (discriminator 1))
__x64_sys_sendto (net/socket.c:2231)
do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1))
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
Freed by task 1543:
kasan_save_stack (mm/kasan/common.c:48)
kasan_save_track (mm/kasan/common.c:60 (discriminator 1) mm/kasan/common.c:69 (discriminator 1))
kasan_save_free_info (mm/kasan/generic.c:579 (discriminator 1))
__kasan_slab_free (mm/kasan/common.c:271)
kmem_cache_free (mm/slub.c:4643 (discriminator 3) mm/slub.c:4745 (discriminator 3))
pskb_expand_head (net/core/skbuff.c:2274)
rpl_do_srh_inline.isra.0 (net/ipv6/rpl_iptunnel.c:158 (discriminator 1))
rpl_input (net/ipv6/rpl_iptunnel.c:201 net/ipv6/rpl_iptunnel.c:282)
lwtunnel_input (net/core/lwtunnel.c:459)
ipv6_rcv (./include/net/dst.h:471 (discriminator 1) ./include/net/dst.h:469 (discriminator 1) net/ipv6/ip6_input.c:79 (discriminator 1) ./include/linux/netfilter.h:317 (discriminator 1) ./include/linux/netfilter.h:311 (discriminator 1) net/ipv6/ip6_input.c:311 (discriminator 1))
__netif_receive_skb_one_core (net/core/dev.c:5967)
process_backlog (./include/linux/rcupdate.h:869 net/core/dev.c:6440)
__napi_poll.constprop.0 (net/core/dev.c:7452)
net_rx_action (net/core/dev.c:7518 net/core/dev.c:7643)
handle_softirqs (kernel/softirq.c:579)
do_softirq (kernel/softirq.c:480 (discriminator 20))
__local_bh_enable_ip (kernel/softirq.c:407)
__dev_queue_xmit (net/core/dev.c:4740)
ip6_finish_output2 (./include/linux/netdevice.h:3358 ./include/net/neighbour.h:526 ./include/net/neighbour.h:540 net/ipv6/ip6_output.c:141)
ip6_finish_output (net/ipv6/ip6_output.c:215 net/ipv6/ip6_output.c:226)
ip6_output (./include/linux/netfilter.h:306 net/ipv6/ip6_output.c:248)
ip6_send_skb (net/ipv6/ip6_output.c:1983)
rawv6_sendmsg (net/ipv6/raw.c:588 net/ipv6/raw.c:918)
__sys_sendto (net/socket.c:714 (discriminator 1) net/socket.c:729 (discriminator 1) net/socket.c:2228 (discriminator 1))
__x64_sys_sendto (net/socket.c:2231)
do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1))
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
The buggy address belongs to the object at ffff888122bf96c0
which belongs to the cache skbuff_small_head of size 704
The buggy address is located 24 bytes inside of
freed 704-byte region [ffff888122bf96c0, ffff888122bf9980)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x122bf8
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x200000000000040(head|node=0|zone=2)
page_type: f5(slab)
raw: 0200000000000040 ffff888101fc0a00 ffffea000464dc00 0000000000000002
raw: 0000000000000000 0000000080270027 00000000f5000000 0000000000000000
head: 0200000000000040 ffff888101fc0a00 ffffea000464dc00 0000000000000002
head: 0000000000000000 0000000080270027 00000000f5000000 0000000000000000
head: 0200000000000003 ffffea00048afe01 00000000ffffffff 00000000ffffffff
head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff888122bf9580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888122bf9600: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff888122bf9680: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
^
ffff888122bf9700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888122bf9780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
Fixes: a7a29f9c361f8 ("net: ipv6: add rpl sr tunnel")
Signed-off-by: Kuniyuki Iwashima <kuniyu@...gle.com>
---
net/ipv6/rpl_iptunnel.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/net/ipv6/rpl_iptunnel.c b/net/ipv6/rpl_iptunnel.c
index 7c05ac846646f..eccfa4203e96b 100644
--- a/net/ipv6/rpl_iptunnel.c
+++ b/net/ipv6/rpl_iptunnel.c
@@ -129,13 +129,13 @@ static int rpl_do_srh_inline(struct sk_buff *skb, const struct rpl_lwt *rlwt,
struct dst_entry *cache_dst)
{
struct ipv6_rpl_sr_hdr *isrh, *csrh;
- const struct ipv6hdr *oldhdr;
+ struct ipv6hdr oldhdr;
struct ipv6hdr *hdr;
unsigned char *buf;
size_t hdrlen;
int err;
- oldhdr = ipv6_hdr(skb);
+ memcpy(&oldhdr, ipv6_hdr(skb), sizeof(oldhdr));
buf = kcalloc(struct_size(srh, segments.addr, srh->segments_left), 2, GFP_ATOMIC);
if (!buf)
@@ -147,7 +147,7 @@ static int rpl_do_srh_inline(struct sk_buff *skb, const struct rpl_lwt *rlwt,
memcpy(isrh, srh, sizeof(*isrh));
memcpy(isrh->rpl_segaddr, &srh->rpl_segaddr[1],
(srh->segments_left - 1) * 16);
- isrh->rpl_segaddr[srh->segments_left - 1] = oldhdr->daddr;
+ isrh->rpl_segaddr[srh->segments_left - 1] = oldhdr.daddr;
ipv6_rpl_srh_compress(csrh, isrh, &srh->rpl_segaddr[0],
isrh->segments_left - 1);
@@ -169,7 +169,7 @@ static int rpl_do_srh_inline(struct sk_buff *skb, const struct rpl_lwt *rlwt,
skb_mac_header_rebuild(skb);
hdr = ipv6_hdr(skb);
- memmove(hdr, oldhdr, sizeof(*hdr));
+ memmove(hdr, &oldhdr, sizeof(*hdr));
isrh = (void *)hdr + sizeof(*hdr);
memcpy(isrh, csrh, hdrlen);
--
2.50.0.727.gbf7dc18ff4-goog
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