[PATCH net] net: prevent NULL pointer dereference in rt_fibinfo_free() and rt_fibinfo_free_cpus()

[PATCH net] net: prevent NULL pointer dereference in rt_fibinfo_free() and rt_fibinfo_free_cpus()

[Jeongjun Park]

rt_fibinfo_free() and rt_fibinfo_free_cpus() only check for rt and do not
verify rt->dst and use it, which will result in NULL pointer dereference.

Therefore, to prevent this, we need to add a check for rt->dst.

Fixes: 0830106c5390 ("ipv4: take dst->__refcnt when caching dst in fib")
Fixes: c5038a8327b9 ("ipv4: Cache routes in nexthop exception entries.")
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
---
 net/ipv4/fib_semantics.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 2b57cd2b96e2..3a2a92599366 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -153,6 +153,8 @@ static void rt_fibinfo_free(struct rtable __rcu **rtp)
 
 	if (!rt)
 		return;
+	if (!&rt->dst)
+		return;
 
 	/* Not even needed : RCU_INIT_POINTER(*rtp, NULL);
 	 * because we waited an RCU grace period before calling
@@ -202,10 +204,13 @@ static void rt_fibinfo_free_cpus(struct rtable __rcu * __percpu *rtp)
 		struct rtable *rt;
 
 		rt = rcu_dereference_protected(*per_cpu_ptr(rtp, cpu), 1);
-		if (rt) {
-			dst_dev_put(&rt->dst);
-			dst_release_immediate(&rt->dst);
-		}
+		if (!rt)
+			continue;
+		if (!&rt->dst)
+			continue;
+
+		dst_dev_put(&rt->dst);
+		dst_release_immediate(&rt->dst);
 	}
 	free_percpu(rtp);
 }
--

Re: [PATCH net] net: prevent NULL pointer dereference in rt_fibinfo_free() and rt_fibinfo_free_cpus()

[Eric Dumazet]

On Mon, Sep 9, 2024 at 8:48 PM Jeongjun Park <aha310510@gmail.com> wrote:
>
> rt_fibinfo_free() and rt_fibinfo_free_cpus() only check for rt and do not
> verify rt->dst and use it, which will result in NULL pointer dereference.
>
> Therefore, to prevent this, we need to add a check for rt->dst.
>
> Fixes: 0830106c5390 ("ipv4: take dst->__refcnt when caching dst in fib")
> Fixes: c5038a8327b9 ("ipv4: Cache routes in nexthop exception entries.")
> Signed-off-by: Jeongjun Park <aha310510@gmail.com>
> ---

As far as I can tell, your patch is a NOP, and these Fixes: tags seem
random to me.

Also, I am guessing this is based on a syzbot report ?

Re: [PATCH net] net: prevent NULL pointer dereference in rt_fibinfo_free() and rt_fibinfo_free_cpus()

[Jeongjun Park]

> Eric Dumazet <edumazet@google.com> wrote:
> On Mon, Sep 9, 2024 at 8:48 PM Jeongjun Park <aha310510@gmail.com> wrote:
>> 
>> rt_fibinfo_free() and rt_fibinfo_free_cpus() only check for rt and do not
>> verify rt->dst and use it, which will result in NULL pointer dereference.
>> 
>> Therefore, to prevent this, we need to add a check for rt->dst.
>> 
>> Fixes: 0830106c5390 ("ipv4: take dst->__refcnt when caching dst in fib")
>> Fixes: c5038a8327b9 ("ipv4: Cache routes in nexthop exception entries.")
>> Signed-off-by: Jeongjun Park <aha310510@gmail.com>
>> ---
> 
> As far as I can tell, your patch is a NOP, and these Fixes: tags seem
> random to me.

I somewhat agree with the opinion that the fixes tag is random. 
However, I think it is absolutely necessary to add a check for 
&rt->dst , because the existence of rt does not guarantee that 
&rt->dst will not be NULL.

> 
> Also, I am guessing this is based on a syzbot report ?

Yes, but it's not a bug reported to syzbot, it's a bug that 
I accidentally found in my syzkaller fuzzer. The report is too long
to be included in the patch notes, so I'll attach it to this email.

Report:

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 UID: 0 PID: 4694 Comm: systemd-udevd Not tainted 6.11.0-rc6-00326-gd1f2d51b711a #16
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
RIP: 0010:dst_dev_put+0x26/0x330 net/core/dst.c:149
Code: 90 90 90 90 f3 0f 1e fa 41 57 41 56 49 89 fe 41 55 41 54 55 e8 0b 90 af f8 4c 89 f2 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 da 02 00 00 49 8d 7e 3a 4d 8b 26 48 b8 00 00 00
RSP: 0018:ffffc90000007d68 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000001 RCX: ffffffff8976519a
RDX: 0000000000000000 RSI: ffffffff88d97a95 RDI: 0000000000000001
RBP: dffffc0000000000 R08: 0000000000000001 R09: ffffed100c8020c3
R10: 0000000000000000 R11: 0000000000000000 R12: fffffbfff1ab5a81
R13: 0000607f8106c5c8 R14: 0000000000000001 R15: 0000000000000000
FS:  00007f235c5fd8c0(0000) GS:ffff88802c400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f39c90e5168 CR3: 0000000019688000 CR4: 0000000000750ef0
PKRU: 55555554
Call Trace:
 <IRQ>
 rt_fibinfo_free_cpus.part.0+0xf4/0x1d0 net/ipv4/fib_semantics.c:206
 rt_fibinfo_free_cpus net/ipv4/fib_semantics.c:198 [inline]
 fib_nh_common_release+0x121/0x360 net/ipv4/fib_semantics.c:217
 fib_nh_release net/ipv4/fib_semantics.c:229 [inline]
 free_fib_info_rcu+0x18f/0x4b0 net/ipv4/fib_semantics.c:241
 rcu_do_batch kernel/rcu/tree.c:2569 [inline]
 rcu_core+0x826/0x16d0 kernel/rcu/tree.c:2843
 handle_softirqs+0x1d4/0x870 kernel/softirq.c:554
 __do_softirq kernel/softirq.c:588 [inline]
 invoke_softirq kernel/softirq.c:428 [inline]
 __irq_exit_rcu kernel/softirq.c:637 [inline]
 irq_exit_rcu+0xbb/0x120 kernel/softirq.c:649
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
 sysvec_apic_timer_interrupt+0x99/0xb0 arch/x86/kernel/apic/apic.c:1043
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x3c/0x70 kernel/locking/spinlock.c:194
Code: 74 24 10 e8 d6 03 6f f6 48 89 ef e8 8e 77 6f f6 81 e3 00 02 00 00 75 29 9c 58 f6 c4 02 75 35 48 85 db 74 01 fb bf 01 00 00 00 e8 bf 24 61 f6 65 8b 05 c0 79 0b 75 85 c0 74 0e 5b 5d c3 cc cc cc
RSP: 0018:ffffc90001f978f8 EFLAGS: 00000206
RAX: 0000000000000006 RBX: 0000000000000200 RCX: 1ffffffff1fe4be9
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001
RBP: ffffffff8dbc0ac0 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffff8ff2a39f R11: ffffffff815d29ca R12: 0000000000000246
R13: ffff88801e866100 R14: 0000000000000200 R15: 0000000000000000
 rcu_read_unlock_special kernel/rcu/tree_plugin.h:691 [inline]
 __rcu_read_unlock+0x2d9/0x580 kernel/rcu/tree_plugin.h:436
 __netlink_sendskb net/netlink/af_netlink.c:1278 [inline]
 netlink_broadcast_deliver net/netlink/af_netlink.c:1408 [inline]
 do_one_broadcast net/netlink/af_netlink.c:1495 [inline]
 netlink_broadcast_filtered+0x8ec/0xe00 net/netlink/af_netlink.c:1540
 netlink_broadcast net/netlink/af_netlink.c:1564 [inline]
 netlink_sendmsg+0x9ee/0xd80 net/netlink/af_netlink.c:1899
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0xabe/0xc80 net/socket.c:2597
 ___sys_sendmsg+0x11d/0x1c0 net/socket.c:2651
 __sys_sendmsg+0xfe/0x1d0 net/socket.c:2680
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcb/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f235c8b0e13
Code: 8b 15 b9 a1 00 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b8 0f 1f 00 64 8b 04 25 18 00 00 00 85 c0 75 14 b8 2e 00 00 00 0f 05 48 3d 00 f0 ff ff 77 55 c3 0f 1f 40 00 48 83 ec 28 89 54 24 1c 48
RSP: 002b:00007ffe93910d38 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000556a6858ba60 RCX: 00007f235c8b0e13
RDX: 0000000000000000 RSI: 00007ffe93910d60 RDI: 000000000000000e
RBP: 0000556a6858bdc0 R08: 00000000ffffffff R09: 0000556a685488e0
R10: 0000556a6858be38 R11: 0000000000000246 R12: 0000000000008010
R13: 0000556a6856fc30 R14: 0000000000000000 R15: 00007ffe93910df0
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:dst_dev_put+0x26/0x330 net/core/dst.c:149
Code: 90 90 90 90 f3 0f 1e fa 41 57 41 56 49 89 fe 41 55 41 54 55 e8 0b 90 af f8 4c 89 f2 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 da 02 00 00 49 8d 7e 3a 4d 8b 26 48 b8 00 00 00
RSP: 0018:ffffc90000007d68 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000001 RCX: ffffffff8976519a
RDX: 0000000000000000 RSI: ffffffff88d97a95 RDI: 0000000000000001
RBP: dffffc0000000000 R08: 0000000000000001 R09: ffffed100c8020c3
R10: 0000000000000000 R11: 0000000000000000 R12: fffffbfff1ab5a81
R13: 0000607f8106c5c8 R14: 0000000000000001 R15: 0000000000000000
FS:  00007f235c5fd8c0(0000) GS:ffff88802c400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f39c90e5168 CR3: 0000000019688000 CR4: 0000000000750ef0
PKRU: 55555554
----------------
Code disassembly (best guess):
   0:	90                   	nop
   1:	90                   	nop
   2:	90                   	nop
   3:	90                   	nop
   4:	f3 0f 1e fa          	endbr64
   8:	41 57                	push   %r15
   a:	41 56                	push   %r14
   c:	49 89 fe             	mov    %rdi,%r14
   f:	41 55                	push   %r13
  11:	41 54                	push   %r12
  13:	55                   	push   %rbp
  14:	e8 0b 90 af f8       	call   0xf8af9024
  19:	4c 89 f2             	mov    %r14,%rdx
  1c:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  23:	fc ff df
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
  2e:	0f 85 da 02 00 00    	jne    0x30e
  34:	49 8d 7e 3a          	lea    0x3a(%r14),%rdi
  38:	4d 8b 26             	mov    (%r14),%r12
  3b:	48                   	rex.W
  3c:	b8                   	.byte 0xb8
  3d:	00 00                	add    %al,(%rax)

Re: [PATCH net] net: prevent NULL pointer dereference in rt_fibinfo_free() and rt_fibinfo_free_cpus()

[Eric Dumazet]

On Tue, Sep 10, 2024 at 5:23 AM Jeongjun Park <aha310510@gmail.com> wrote:
>
>
> > Eric Dumazet <edumazet@google.com> wrote:
> > On Mon, Sep 9, 2024 at 8:48 PM Jeongjun Park <aha310510@gmail.com> wrote:
> >>
> >> rt_fibinfo_free() and rt_fibinfo_free_cpus() only check for rt and do not
> >> verify rt->dst and use it, which will result in NULL pointer dereference.
> >>
> >> Therefore, to prevent this, we need to add a check for rt->dst.
> >>
> >> Fixes: 0830106c5390 ("ipv4: take dst->__refcnt when caching dst in fib")
> >> Fixes: c5038a8327b9 ("ipv4: Cache routes in nexthop exception entries.")
> >> Signed-off-by: Jeongjun Park <aha310510@gmail.com>
> >> ---
> >
> > As far as I can tell, your patch is a NOP, and these Fixes: tags seem
> > random to me.
>
> I somewhat agree with the opinion that the fixes tag is random.
> However, I think it is absolutely necessary to add a check for
> &rt->dst , because the existence of rt does not guarantee that
> &rt->dst will not be NULL.

dst is the first field of 'struct rtable'.

Always has been.

Unless your compiler is buggy, (void *)rt == (void *)&rt->dst

Re: [PATCH net] net: prevent NULL pointer dereference in rt_fibinfo_free() and rt_fibinfo_free_cpus()

[Eric Dumazet]

On Tue, Sep 10, 2024 at 5:23 AM Jeongjun Park <aha310510@gmail.com> wrote:
>
>
> > Eric Dumazet <edumazet@google.com> wrote:
> > On Mon, Sep 9, 2024 at 8:48 PM Jeongjun Park <aha310510@gmail.com> wrote:
> >>
> >> rt_fibinfo_free() and rt_fibinfo_free_cpus() only check for rt and do not
> >> verify rt->dst and use it, which will result in NULL pointer dereference.
> >>
> >> Therefore, to prevent this, we need to add a check for rt->dst.
> >>
> >> Fixes: 0830106c5390 ("ipv4: take dst->__refcnt when caching dst in fib")
> >> Fixes: c5038a8327b9 ("ipv4: Cache routes in nexthop exception entries.")
> >> Signed-off-by: Jeongjun Park <aha310510@gmail.com>
> >> ---
> >
> > As far as I can tell, your patch is a NOP, and these Fixes: tags seem
> > random to me.
>
> I somewhat agree with the opinion that the fixes tag is random.
> However, I think it is absolutely necessary to add a check for
> &rt->dst , because the existence of rt does not guarantee that
> &rt->dst will not be NULL.
>
> >
> > Also, I am guessing this is based on a syzbot report ?
>
> Yes, but it's not a bug reported to syzbot, it's a bug that
> I accidentally found in my syzkaller fuzzer. The report is too long
> to be included in the patch notes, so I'll attach it to this email.

syzbot has a similar report in its queue, I put it on hold because
this is some unrelated memory corruption.

rt (R14 in your case) is 0x1 at this point, which is not a valid memory pointer.

So I am definitely saying no to your patch.

>
> Report:
>
> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN NOPTI
> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> CPU: 0 UID: 0 PID: 4694 Comm: systemd-udevd Not tainted 6.11.0-rc6-00326-gd1f2d51b711a #16
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
> RIP: 0010:dst_dev_put+0x26/0x330 net/core/dst.c:149
> Code: 90 90 90 90 f3 0f 1e fa 41 57 41 56 49 89 fe 41 55 41 54 55 e8 0b 90 af f8 4c 89 f2 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 da 02 00 00 49 8d 7e 3a 4d 8b 26 48 b8 00 00 00
> RSP: 0018:ffffc90000007d68 EFLAGS: 00010246
> RAX: dffffc0000000000 RBX: 0000000000000001 RCX: ffffffff8976519a
> RDX: 0000000000000000 RSI: ffffffff88d97a95 RDI: 0000000000000001
> RBP: dffffc0000000000 R08: 0000000000000001 R09: ffffed100c8020c3
> R10: 0000000000000000 R11: 0000000000000000 R12: fffffbfff1ab5a81
> R13: 0000607f8106c5c8 R14: 0000000000000001 R15: 0000000000000000
> FS:  00007f235c5fd8c0(0000) GS:ffff88802c400000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f39c90e5168 CR3: 0000000019688000 CR4: 0000000000750ef0
> PKRU: 55555554
> Call Trace:
>  <IRQ>
>  rt_fibinfo_free_cpus.part.0+0xf4/0x1d0 net/ipv4/fib_semantics.c:206
>  rt_fibinfo_free_cpus net/ipv4/fib_semantics.c:198 [inline]
>  fib_nh_common_release+0x121/0x360 net/ipv4/fib_semantics.c:217
>  fib_nh_release net/ipv4/fib_semantics.c:229 [inline]
>  free_fib_info_rcu+0x18f/0x4b0 net/ipv4/fib_semantics.c:241
>  rcu_do_batch kernel/rcu/tree.c:2569 [inline]
>  rcu_core+0x826/0x16d0 kernel/rcu/tree.c:2843
>  handle_softirqs+0x1d4/0x870 kernel/softirq.c:554
>  __do_softirq kernel/softirq.c:588 [inline]
>  invoke_softirq kernel/softirq.c:428 [inline]
>  __irq_exit_rcu kernel/softirq.c:637 [inline]
>  irq_exit_rcu+0xbb/0x120 kernel/softirq.c:649
>  instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
>  sysvec_apic_timer_interrupt+0x99/0xb0 arch/x86/kernel/apic/apic.c:1043
>  </IRQ>
>  <TASK>
>  asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
> RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
> RIP: 0010:_raw_spin_unlock_irqrestore+0x3c/0x70 kernel/locking/spinlock.c:194
> Code: 74 24 10 e8 d6 03 6f f6 48 89 ef e8 8e 77 6f f6 81 e3 00 02 00 00 75 29 9c 58 f6 c4 02 75 35 48 85 db 74 01 fb bf 01 00 00 00 e8 bf 24 61 f6 65 8b 05 c0 79 0b 75 85 c0 74 0e 5b 5d c3 cc cc cc
> RSP: 0018:ffffc90001f978f8 EFLAGS: 00000206
> RAX: 0000000000000006 RBX: 0000000000000200 RCX: 1ffffffff1fe4be9
> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001
> RBP: ffffffff8dbc0ac0 R08: 0000000000000001 R09: 0000000000000001
> R10: ffffffff8ff2a39f R11: ffffffff815d29ca R12: 0000000000000246
> R13: ffff88801e866100 R14: 0000000000000200 R15: 0000000000000000
>  rcu_read_unlock_special kernel/rcu/tree_plugin.h:691 [inline]
>  __rcu_read_unlock+0x2d9/0x580 kernel/rcu/tree_plugin.h:436
>  __netlink_sendskb net/netlink/af_netlink.c:1278 [inline]
>  netlink_broadcast_deliver net/netlink/af_netlink.c:1408 [inline]
>  do_one_broadcast net/netlink/af_netlink.c:1495 [inline]
>  netlink_broadcast_filtered+0x8ec/0xe00 net/netlink/af_netlink.c:1540
>  netlink_broadcast net/netlink/af_netlink.c:1564 [inline]
>  netlink_sendmsg+0x9ee/0xd80 net/netlink/af_netlink.c:1899
>  sock_sendmsg_nosec net/socket.c:730 [inline]
>  __sock_sendmsg net/socket.c:745 [inline]
>  ____sys_sendmsg+0xabe/0xc80 net/socket.c:2597
>  ___sys_sendmsg+0x11d/0x1c0 net/socket.c:2651
>  __sys_sendmsg+0xfe/0x1d0 net/socket.c:2680
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcb/0x250 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f235c8b0e13
> Code: 8b 15 b9 a1 00 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b8 0f 1f 00 64 8b 04 25 18 00 00 00 85 c0 75 14 b8 2e 00 00 00 0f 05 48 3d 00 f0 ff ff 77 55 c3 0f 1f 40 00 48 83 ec 28 89 54 24 1c 48
> RSP: 002b:00007ffe93910d38 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> RAX: ffffffffffffffda RBX: 0000556a6858ba60 RCX: 00007f235c8b0e13
> RDX: 0000000000000000 RSI: 00007ffe93910d60 RDI: 000000000000000e
> RBP: 0000556a6858bdc0 R08: 00000000ffffffff R09: 0000556a685488e0
> R10: 0000556a6858be38 R11: 0000000000000246 R12: 0000000000008010
> R13: 0000556a6856fc30 R14: 0000000000000000 R15: 00007ffe93910df0
>  </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:dst_dev_put+0x26/0x330 net/core/dst.c:149
> Code: 90 90 90 90 f3 0f 1e fa 41 57 41 56 49 89 fe 41 55 41 54 55 e8 0b 90 af f8 4c 89 f2 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 da 02 00 00 49 8d 7e 3a 4d 8b 26 48 b8 00 00 00
> RSP: 0018:ffffc90000007d68 EFLAGS: 00010246
> RAX: dffffc0000000000 RBX: 0000000000000001 RCX: ffffffff8976519a
> RDX: 0000000000000000 RSI: ffffffff88d97a95 RDI: 0000000000000001
> RBP: dffffc0000000000 R08: 0000000000000001 R09: ffffed100c8020c3
> R10: 0000000000000000 R11: 0000000000000000 R12: fffffbfff1ab5a81
> R13: 0000607f8106c5c8 R14: 0000000000000001 R15: 0000000000000000
> FS:  00007f235c5fd8c0(0000) GS:ffff88802c400000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f39c90e5168 CR3: 0000000019688000 CR4: 0000000000750ef0
> PKRU: 55555554
> ----------------
> Code disassembly (best guess):
>    0:   90                      nop
>    1:   90                      nop
>    2:   90                      nop
>    3:   90                      nop
>    4:   f3 0f 1e fa             endbr64
>    8:   41 57                   push   %r15
>    a:   41 56                   push   %r14
>    c:   49 89 fe                mov    %rdi,%r14
>    f:   41 55                   push   %r13
>   11:   41 54                   push   %r12
>   13:   55                      push   %rbp
>   14:   e8 0b 90 af f8          call   0xf8af9024
>   19:   4c 89 f2                mov    %r14,%rdx
>   1c:   48 b8 00 00 00 00 00    movabs $0xdffffc0000000000,%rax
>   23:   fc ff df
>   26:   48 c1 ea 03             shr    $0x3,%rdx
> * 2a:   80 3c 02 00             cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
>   2e:   0f 85 da 02 00 00       jne    0x30e
>   34:   49 8d 7e 3a             lea    0x3a(%r14),%rdi
>   38:   4d 8b 26                mov    (%r14),%r12
>   3b:   48                      rex.W
>   3c:   b8                      .byte 0xb8
>   3d:   00 00                   add    %al,(%rax)

Re: [PATCH net] net: prevent NULL pointer dereference in rt_fibinfo_free() and rt_fibinfo_free_cpus()

[Jeongjun Park]

Eric Dumazet <edumazet@google.com> wrote:
>
> On Tue, Sep 10, 2024 at 5:23 AM Jeongjun Park <aha310510@gmail.com> wrote:
> >
> >
> > > Eric Dumazet <edumazet@google.com> wrote:
> > > On Mon, Sep 9, 2024 at 8:48 PM Jeongjun Park <aha310510@gmail.com> wrote:
> > >>
> > >> rt_fibinfo_free() and rt_fibinfo_free_cpus() only check for rt and do not
> > >> verify rt->dst and use it, which will result in NULL pointer dereference.
> > >>
> > >> Therefore, to prevent this, we need to add a check for rt->dst.
> > >>
> > >> Fixes: 0830106c5390 ("ipv4: take dst->__refcnt when caching dst in fib")
> > >> Fixes: c5038a8327b9 ("ipv4: Cache routes in nexthop exception entries.")
> > >> Signed-off-by: Jeongjun Park <aha310510@gmail.com>
> > >> ---
> > >
> > > As far as I can tell, your patch is a NOP, and these Fixes: tags seem
> > > random to me.
> >
> > I somewhat agree with the opinion that the fixes tag is random.
> > However, I think it is absolutely necessary to add a check for
> > &rt->dst , because the existence of rt does not guarantee that
> > &rt->dst will not be NULL.
> >
> > >
> > > Also, I am guessing this is based on a syzbot report ?
> >
> > Yes, but it's not a bug reported to syzbot, it's a bug that
> > I accidentally found in my syzkaller fuzzer. The report is too long
> > to be included in the patch notes, so I'll attach it to this email.
>
> syzbot has a similar report in its queue, I put it on hold because
> this is some unrelated memory corruption.
>
> rt (R14 in your case) is 0x1 at this point, which is not a valid memory pointer.
>
> So I am definitely saying no to your patch.
>

I see. Thanks to the explanation, I understood that this patch is wrong.

However, while continuing to analyze this bug, I found out something.
According to the rcu_dereference_protected() doc, when using
rcu_dereference_protected(), it is specified that ptr should be protected
using a lock, but free_fib_info_rcu() does not have any protection for
the fib_info structure.

I think this may cause a data-race, which modifies the values of rt and
&rt->dst, causing the bug. Even if this is not the root cause, I don't
think there is a reason why free_fib_info_rcu() should not be protected
with fib_info_lock.

What do you think about protecting the fib_info structure like the patch
below?

Regards,
Jeongjun Park

---
 net/ipv4/fib_semantics.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 2b57cd2b96e2..77431879ee39 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -234,6 +234,7 @@ static void free_fib_info_rcu(struct rcu_head *head)
 {
    struct fib_info *fi = container_of(head, struct fib_info, rcu);

+   spin_lock(&fib_info_lock);
    if (fi->nh) {
        nexthop_put(fi->nh);
    } else {
@@ -245,6 +246,7 @@ static void free_fib_info_rcu(struct rcu_head *head)
    ip_fib_metrics_put(fi->fib_metrics);

    kfree(fi);
+   spin_unlock(&fib_info_lock);
 }

 void free_fib_info(struct fib_info *fi)
--

> >
> > Report:
> >
> > Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN NOPTI
> > KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> > CPU: 0 UID: 0 PID: 4694 Comm: systemd-udevd Not tainted 6.11.0-rc6-00326-gd1f2d51b711a #16
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
> > RIP: 0010:dst_dev_put+0x26/0x330 net/core/dst.c:149
> > Code: 90 90 90 90 f3 0f 1e fa 41 57 41 56 49 89 fe 41 55 41 54 55 e8 0b 90 af f8 4c 89 f2 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 da 02 00 00 49 8d 7e 3a 4d 8b 26 48 b8 00 00 00
> > RSP: 0018:ffffc90000007d68 EFLAGS: 00010246
> > RAX: dffffc0000000000 RBX: 0000000000000001 RCX: ffffffff8976519a
> > RDX: 0000000000000000 RSI: ffffffff88d97a95 RDI: 0000000000000001
> > RBP: dffffc0000000000 R08: 0000000000000001 R09: ffffed100c8020c3
> > R10: 0000000000000000 R11: 0000000000000000 R12: fffffbfff1ab5a81
> > R13: 0000607f8106c5c8 R14: 0000000000000001 R15: 0000000000000000
> > FS:  00007f235c5fd8c0(0000) GS:ffff88802c400000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00007f39c90e5168 CR3: 0000000019688000 CR4: 0000000000750ef0
> > PKRU: 55555554
> > Call Trace:
> >  <IRQ>
> >  rt_fibinfo_free_cpus.part.0+0xf4/0x1d0 net/ipv4/fib_semantics.c:206
> >  rt_fibinfo_free_cpus net/ipv4/fib_semantics.c:198 [inline]
> >  fib_nh_common_release+0x121/0x360 net/ipv4/fib_semantics.c:217
> >  fib_nh_release net/ipv4/fib_semantics.c:229 [inline]
> >  free_fib_info_rcu+0x18f/0x4b0 net/ipv4/fib_semantics.c:241
> >  rcu_do_batch kernel/rcu/tree.c:2569 [inline]
> >  rcu_core+0x826/0x16d0 kernel/rcu/tree.c:2843
> >  handle_softirqs+0x1d4/0x870 kernel/softirq.c:554
> >  __do_softirq kernel/softirq.c:588 [inline]
> >  invoke_softirq kernel/softirq.c:428 [inline]
> >  __irq_exit_rcu kernel/softirq.c:637 [inline]
> >  irq_exit_rcu+0xbb/0x120 kernel/softirq.c:649
> >  instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
> >  sysvec_apic_timer_interrupt+0x99/0xb0 arch/x86/kernel/apic/apic.c:1043
> >  </IRQ>
> >  <TASK>
> >  asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
> > RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
> > RIP: 0010:_raw_spin_unlock_irqrestore+0x3c/0x70 kernel/locking/spinlock.c:194
> > Code: 74 24 10 e8 d6 03 6f f6 48 89 ef e8 8e 77 6f f6 81 e3 00 02 00 00 75 29 9c 58 f6 c4 02 75 35 48 85 db 74 01 fb bf 01 00 00 00 e8 bf 24 61 f6 65 8b 05 c0 79 0b 75 85 c0 74 0e 5b 5d c3 cc cc cc
> > RSP: 0018:ffffc90001f978f8 EFLAGS: 00000206
> > RAX: 0000000000000006 RBX: 0000000000000200 RCX: 1ffffffff1fe4be9
> > RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001
> > RBP: ffffffff8dbc0ac0 R08: 0000000000000001 R09: 0000000000000001
> > R10: ffffffff8ff2a39f R11: ffffffff815d29ca R12: 0000000000000246
> > R13: ffff88801e866100 R14: 0000000000000200 R15: 0000000000000000
> >  rcu_read_unlock_special kernel/rcu/tree_plugin.h:691 [inline]
> >  __rcu_read_unlock+0x2d9/0x580 kernel/rcu/tree_plugin.h:436
> >  __netlink_sendskb net/netlink/af_netlink.c:1278 [inline]
> >  netlink_broadcast_deliver net/netlink/af_netlink.c:1408 [inline]
> >  do_one_broadcast net/netlink/af_netlink.c:1495 [inline]
> >  netlink_broadcast_filtered+0x8ec/0xe00 net/netlink/af_netlink.c:1540
> >  netlink_broadcast net/netlink/af_netlink.c:1564 [inline]
> >  netlink_sendmsg+0x9ee/0xd80 net/netlink/af_netlink.c:1899
> >  sock_sendmsg_nosec net/socket.c:730 [inline]
> >  __sock_sendmsg net/socket.c:745 [inline]
> >  ____sys_sendmsg+0xabe/0xc80 net/socket.c:2597
> >  ___sys_sendmsg+0x11d/0x1c0 net/socket.c:2651
> >  __sys_sendmsg+0xfe/0x1d0 net/socket.c:2680
> >  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> >  do_syscall_64+0xcb/0x250 arch/x86/entry/common.c:83
> >  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > RIP: 0033:0x7f235c8b0e13
> > Code: 8b 15 b9 a1 00 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b8 0f 1f 00 64 8b 04 25 18 00 00 00 85 c0 75 14 b8 2e 00 00 00 0f 05 48 3d 00 f0 ff ff 77 55 c3 0f 1f 40 00 48 83 ec 28 89 54 24 1c 48
> > RSP: 002b:00007ffe93910d38 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> > RAX: ffffffffffffffda RBX: 0000556a6858ba60 RCX: 00007f235c8b0e13
> > RDX: 0000000000000000 RSI: 00007ffe93910d60 RDI: 000000000000000e
> > RBP: 0000556a6858bdc0 R08: 00000000ffffffff R09: 0000556a685488e0
> > R10: 0000556a6858be38 R11: 0000000000000246 R12: 0000000000008010
> > R13: 0000556a6856fc30 R14: 0000000000000000 R15: 00007ffe93910df0
> >  </TASK>
> > Modules linked in:
> > ---[ end trace 0000000000000000 ]---
> > RIP: 0010:dst_dev_put+0x26/0x330 net/core/dst.c:149
> > Code: 90 90 90 90 f3 0f 1e fa 41 57 41 56 49 89 fe 41 55 41 54 55 e8 0b 90 af f8 4c 89 f2 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 da 02 00 00 49 8d 7e 3a 4d 8b 26 48 b8 00 00 00
> > RSP: 0018:ffffc90000007d68 EFLAGS: 00010246
> > RAX: dffffc0000000000 RBX: 0000000000000001 RCX: ffffffff8976519a
> > RDX: 0000000000000000 RSI: ffffffff88d97a95 RDI: 0000000000000001
> > RBP: dffffc0000000000 R08: 0000000000000001 R09: ffffed100c8020c3
> > R10: 0000000000000000 R11: 0000000000000000 R12: fffffbfff1ab5a81
> > R13: 0000607f8106c5c8 R14: 0000000000000001 R15: 0000000000000000
> > FS:  00007f235c5fd8c0(0000) GS:ffff88802c400000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00007f39c90e5168 CR3: 0000000019688000 CR4: 0000000000750ef0
> > PKRU: 55555554
> > ----------------
> > Code disassembly (best guess):
> >    0:   90                      nop
> >    1:   90                      nop
> >    2:   90                      nop
> >    3:   90                      nop
> >    4:   f3 0f 1e fa             endbr64
> >    8:   41 57                   push   %r15
> >    a:   41 56                   push   %r14
> >    c:   49 89 fe                mov    %rdi,%r14
> >    f:   41 55                   push   %r13
> >   11:   41 54                   push   %r12
> >   13:   55                      push   %rbp
> >   14:   e8 0b 90 af f8          call   0xf8af9024
> >   19:   4c 89 f2                mov    %r14,%rdx
> >   1c:   48 b8 00 00 00 00 00    movabs $0xdffffc0000000000,%rax
> >   23:   fc ff df
> >   26:   48 c1 ea 03             shr    $0x3,%rdx
> > * 2a:   80 3c 02 00             cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
> >   2e:   0f 85 da 02 00 00       jne    0x30e
> >   34:   49 8d 7e 3a             lea    0x3a(%r14),%rdi
> >   38:   4d 8b 26                mov    (%r14),%r12
> >   3b:   48                      rex.W
> >   3c:   b8                      .byte 0xb8
> >   3d:   00 00                   add    %al,(%rax)

Re: [PATCH net] net: prevent NULL pointer dereference in rt_fibinfo_free() and rt_fibinfo_free_cpus()

[Eric Dumazet]

On Tue, Sep 10, 2024 at 4:06 PM Jeongjun Park <aha310510@gmail.com> wrote:
>
> Eric Dumazet <edumazet@google.com> wrote:
> >
> > On Tue, Sep 10, 2024 at 5:23 AM Jeongjun Park <aha310510@gmail.com> wrote:
> > >
> > >
> > > > Eric Dumazet <edumazet@google.com> wrote:
> > > > On Mon, Sep 9, 2024 at 8:48 PM Jeongjun Park <aha310510@gmail.com> wrote:
> > > >>
> > > >> rt_fibinfo_free() and rt_fibinfo_free_cpus() only check for rt and do not
> > > >> verify rt->dst and use it, which will result in NULL pointer dereference.
> > > >>
> > > >> Therefore, to prevent this, we need to add a check for rt->dst.
> > > >>
> > > >> Fixes: 0830106c5390 ("ipv4: take dst->__refcnt when caching dst in fib")
> > > >> Fixes: c5038a8327b9 ("ipv4: Cache routes in nexthop exception entries.")
> > > >> Signed-off-by: Jeongjun Park <aha310510@gmail.com>
> > > >> ---
> > > >
> > > > As far as I can tell, your patch is a NOP, and these Fixes: tags seem
> > > > random to me.
> > >
> > > I somewhat agree with the opinion that the fixes tag is random.
> > > However, I think it is absolutely necessary to add a check for
> > > &rt->dst , because the existence of rt does not guarantee that
> > > &rt->dst will not be NULL.
> > >
> > > >
> > > > Also, I am guessing this is based on a syzbot report ?
> > >
> > > Yes, but it's not a bug reported to syzbot, it's a bug that
> > > I accidentally found in my syzkaller fuzzer. The report is too long
> > > to be included in the patch notes, so I'll attach it to this email.
> >
> > syzbot has a similar report in its queue, I put it on hold because
> > this is some unrelated memory corruption.
> >
> > rt (R14 in your case) is 0x1 at this point, which is not a valid memory pointer.
> >
> > So I am definitely saying no to your patch.
> >
>
> I see. Thanks to the explanation, I understood that this patch is wrong.
>
> However, while continuing to analyze this bug, I found out something.
> According to the rcu_dereference_protected() doc, when using
> rcu_dereference_protected(), it is specified that ptr should be protected
> using a lock, but free_fib_info_rcu() does not have any protection for
> the fib_info structure.
>
> I think this may cause a data-race, which modifies the values of rt and
> &rt->dst, causing the bug. Even if this is not the root cause, I don't
> think there is a reason why free_fib_info_rcu() should not be protected
> with fib_info_lock.
>
> What do you think about protecting the fib_info structure like the patch
> below?
>

By the time free_fib_info_rcu() is called, we have the guarantee that
no other threads/cpu can possibly use the
struct fib_info.

nexthop_put(), fib_nh_release(), ip_fib_metrics_put, kfree() do not
need this spinlock protection.

fib_info_lock has absolutely no effect here.

Also, 0x1 is not a valid pointer, there is absolutely no chance a
network layer could use 0x1 as a rt/dst pointer.

As I said, the bug is elsewhere, something is mangling some piece of memory.

Re: [PATCH net] net: prevent NULL pointer dereference in rt_fibinfo_free() and rt_fibinfo_free_cpus()

[kernel test robot]

Hi Jeongjun,

kernel test robot noticed the following build warnings:

[auto build test WARNING on net/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Jeongjun-Park/net-prevent-NULL-pointer-dereference-in-rt_fibinfo_free-and-rt_fibinfo_free_cpus/20240910-025008
base:   net/main
patch link:    https://lore.kernel.org/r/20240909184827.123071-1-aha310510%40gmail.com
patch subject: [PATCH net] net: prevent NULL pointer dereference in rt_fibinfo_free() and rt_fibinfo_free_cpus()
config: arc-randconfig-002-20240910 (https://download.01.org/0day-ci/archive/20240910/202409102210.krjQJVRr-lkp@intel.com/config)
compiler: arc-elf-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240910/202409102210.krjQJVRr-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202409102210.krjQJVRr-lkp@intel.com/

All warnings (new ones prefixed by >>):

   net/ipv4/fib_semantics.c: In function 'rt_fibinfo_free':
>> net/ipv4/fib_semantics.c:156:13: warning: the comparison will always evaluate as 'true' for the address of 'dst' will never be NULL [-Waddress]
     156 |         if (!&rt->dst)
         |             ^
   In file included from include/net/ip.h:30,
                    from net/ipv4/fib_semantics.c:37:
   include/net/route.h:56:33: note: 'dst' declared here
      56 |         struct dst_entry        dst;
         |                                 ^~~
   net/ipv4/fib_semantics.c: In function 'rt_fibinfo_free_cpus':
   net/ipv4/fib_semantics.c:209:21: warning: the comparison will always evaluate as 'true' for the address of 'dst' will never be NULL [-Waddress]
     209 |                 if (!&rt->dst)
         |                     ^
   include/net/route.h:56:33: note: 'dst' declared here
      56 |         struct dst_entry        dst;
         |                                 ^~~


vim +156 net/ipv4/fib_semantics.c

   149	
   150	static void rt_fibinfo_free(struct rtable __rcu **rtp)
   151	{
   152		struct rtable *rt = rcu_dereference_protected(*rtp, 1);
   153	
   154		if (!rt)
   155			return;
 > 156		if (!&rt->dst)
   157			return;
   158	
   159		/* Not even needed : RCU_INIT_POINTER(*rtp, NULL);
   160		 * because we waited an RCU grace period before calling
   161		 * free_fib_info_rcu()
   162		 */
   163	
   164		dst_dev_put(&rt->dst);
   165		dst_release_immediate(&rt->dst);
   166	}
   167	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH net] net: prevent NULL pointer dereference in rt_fibinfo_free() and rt_fibinfo_free_cpus()

[kernel test robot]

Hi Jeongjun,

kernel test robot noticed the following build warnings:

[auto build test WARNING on net/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Jeongjun-Park/net-prevent-NULL-pointer-dereference-in-rt_fibinfo_free-and-rt_fibinfo_free_cpus/20240910-025008
base:   net/main
patch link:    https://lore.kernel.org/r/20240909184827.123071-1-aha310510%40gmail.com
patch subject: [PATCH net] net: prevent NULL pointer dereference in rt_fibinfo_free() and rt_fibinfo_free_cpus()
config: arm-randconfig-001-20240910 (https://download.01.org/0day-ci/archive/20240911/202409110000.E9IVjdB7-lkp@intel.com/config)
compiler: clang version 20.0.0git (https://github.com/llvm/llvm-project 05f5a91d00b02f4369f46d076411c700755ae041)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240911/202409110000.E9IVjdB7-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202409110000.E9IVjdB7-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from net/ipv4/fib_semantics.c:17:
   In file included from include/linux/mm.h:2232:
   include/linux/vmstat.h:517:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
     517 |         return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
         |                               ~~~~~~~~~~~ ^ ~~~
>> net/ipv4/fib_semantics.c:156:12: warning: address of 'rt->dst' will always evaluate to 'true' [-Wpointer-bool-conversion]
     156 |         if (!&rt->dst)
         |             ~ ~~~~^~~
   net/ipv4/fib_semantics.c:209:13: warning: address of 'rt->dst' will always evaluate to 'true' [-Wpointer-bool-conversion]
     209 |                 if (!&rt->dst)
         |                     ~ ~~~~^~~
   3 warnings generated.


vim +156 net/ipv4/fib_semantics.c

  > 17	#include <linux/mm.h>
    18	#include <linux/string.h>
    19	#include <linux/socket.h>
    20	#include <linux/sockios.h>
    21	#include <linux/errno.h>
    22	#include <linux/in.h>
    23	#include <linux/inet.h>
    24	#include <linux/inetdevice.h>
    25	#include <linux/netdevice.h>
    26	#include <linux/if_arp.h>
    27	#include <linux/proc_fs.h>
    28	#include <linux/skbuff.h>
    29	#include <linux/init.h>
    30	#include <linux/slab.h>
    31	#include <linux/netlink.h>
    32	#include <linux/hash.h>
    33	#include <linux/nospec.h>
    34	
    35	#include <net/arp.h>
    36	#include <net/inet_dscp.h>
    37	#include <net/ip.h>
    38	#include <net/protocol.h>
    39	#include <net/route.h>
    40	#include <net/tcp.h>
    41	#include <net/sock.h>
    42	#include <net/ip_fib.h>
    43	#include <net/ip6_fib.h>
    44	#include <net/nexthop.h>
    45	#include <net/netlink.h>
    46	#include <net/rtnh.h>
    47	#include <net/lwtunnel.h>
    48	#include <net/fib_notifier.h>
    49	#include <net/addrconf.h>
    50	
    51	#include "fib_lookup.h"
    52	
    53	static DEFINE_SPINLOCK(fib_info_lock);
    54	static struct hlist_head *fib_info_hash;
    55	static struct hlist_head *fib_info_laddrhash;
    56	static unsigned int fib_info_hash_size;
    57	static unsigned int fib_info_hash_bits;
    58	static unsigned int fib_info_cnt;
    59	
    60	#define DEVINDEX_HASHBITS 8
    61	#define DEVINDEX_HASHSIZE (1U << DEVINDEX_HASHBITS)
    62	static struct hlist_head fib_info_devhash[DEVINDEX_HASHSIZE];
    63	
    64	/* for_nexthops and change_nexthops only used when nexthop object
    65	 * is not set in a fib_info. The logic within can reference fib_nh.
    66	 */
    67	#ifdef CONFIG_IP_ROUTE_MULTIPATH
    68	
    69	#define for_nexthops(fi) {						\
    70		int nhsel; const struct fib_nh *nh;				\
    71		for (nhsel = 0, nh = (fi)->fib_nh;				\
    72		     nhsel < fib_info_num_path((fi));				\
    73		     nh++, nhsel++)
    74	
    75	#define change_nexthops(fi) {						\
    76		int nhsel; struct fib_nh *nexthop_nh;				\
    77		for (nhsel = 0,	nexthop_nh = (struct fib_nh *)((fi)->fib_nh);	\
    78		     nhsel < fib_info_num_path((fi));				\
    79		     nexthop_nh++, nhsel++)
    80	
    81	#else /* CONFIG_IP_ROUTE_MULTIPATH */
    82	
    83	/* Hope, that gcc will optimize it to get rid of dummy loop */
    84	
    85	#define for_nexthops(fi) {						\
    86		int nhsel; const struct fib_nh *nh = (fi)->fib_nh;		\
    87		for (nhsel = 0; nhsel < 1; nhsel++)
    88	
    89	#define change_nexthops(fi) {						\
    90		int nhsel;							\
    91		struct fib_nh *nexthop_nh = (struct fib_nh *)((fi)->fib_nh);	\
    92		for (nhsel = 0; nhsel < 1; nhsel++)
    93	
    94	#endif /* CONFIG_IP_ROUTE_MULTIPATH */
    95	
    96	#define endfor_nexthops(fi) }
    97	
    98	
    99	const struct fib_prop fib_props[RTN_MAX + 1] = {
   100		[RTN_UNSPEC] = {
   101			.error	= 0,
   102			.scope	= RT_SCOPE_NOWHERE,
   103		},
   104		[RTN_UNICAST] = {
   105			.error	= 0,
   106			.scope	= RT_SCOPE_UNIVERSE,
   107		},
   108		[RTN_LOCAL] = {
   109			.error	= 0,
   110			.scope	= RT_SCOPE_HOST,
   111		},
   112		[RTN_BROADCAST] = {
   113			.error	= 0,
   114			.scope	= RT_SCOPE_LINK,
   115		},
   116		[RTN_ANYCAST] = {
   117			.error	= 0,
   118			.scope	= RT_SCOPE_LINK,
   119		},
   120		[RTN_MULTICAST] = {
   121			.error	= 0,
   122			.scope	= RT_SCOPE_UNIVERSE,
   123		},
   124		[RTN_BLACKHOLE] = {
   125			.error	= -EINVAL,
   126			.scope	= RT_SCOPE_UNIVERSE,
   127		},
   128		[RTN_UNREACHABLE] = {
   129			.error	= -EHOSTUNREACH,
   130			.scope	= RT_SCOPE_UNIVERSE,
   131		},
   132		[RTN_PROHIBIT] = {
   133			.error	= -EACCES,
   134			.scope	= RT_SCOPE_UNIVERSE,
   135		},
   136		[RTN_THROW] = {
   137			.error	= -EAGAIN,
   138			.scope	= RT_SCOPE_UNIVERSE,
   139		},
   140		[RTN_NAT] = {
   141			.error	= -EINVAL,
   142			.scope	= RT_SCOPE_NOWHERE,
   143		},
   144		[RTN_XRESOLVE] = {
   145			.error	= -EINVAL,
   146			.scope	= RT_SCOPE_NOWHERE,
   147		},
   148	};
   149	
   150	static void rt_fibinfo_free(struct rtable __rcu **rtp)
   151	{
   152		struct rtable *rt = rcu_dereference_protected(*rtp, 1);
   153	
   154		if (!rt)
   155			return;
 > 156		if (!&rt->dst)
   157			return;
   158	
   159		/* Not even needed : RCU_INIT_POINTER(*rtp, NULL);
   160		 * because we waited an RCU grace period before calling
   161		 * free_fib_info_rcu()
   162		 */
   163	
   164		dst_dev_put(&rt->dst);
   165		dst_release_immediate(&rt->dst);
   166	}
   167	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki