[PATCH net] net: avoid potential UAF in default_operstate()

[PATCH net] net: avoid potential UAF in default_operstate()

[Eric Dumazet]

syzbot reported an UAF in default_operstate() [1]

Issue is a race between device and netns dismantles.

After calling __rtnl_unlock() from netdev_run_todo(),
we can not assume the netns of each device is still alive.

Make sure the device is not in NETREG_UNREGISTERED state,
and add an ASSERT_RTNL() before the call to
__dev_get_by_index().

We might move this ASSERT_RTNL() in __dev_get_by_index()
in the future.

[1]

BUG: KASAN: slab-use-after-free in __dev_get_by_index+0x5d/0x110 net/core/dev.c:852
Read of size 8 at addr ffff888043eba1b0 by task syz.0.0/5339

CPU: 0 UID: 0 PID: 5339 Comm: syz.0.0 Not tainted 6.12.0-syzkaller-10296-gaaf20f870da0 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
  __dump_stack lib/dump_stack.c:94 [inline]
  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
  print_address_description mm/kasan/report.c:378 [inline]
  print_report+0x169/0x550 mm/kasan/report.c:489
  kasan_report+0x143/0x180 mm/kasan/report.c:602
  __dev_get_by_index+0x5d/0x110 net/core/dev.c:852
  default_operstate net/core/link_watch.c:51 [inline]
  rfc2863_policy+0x224/0x300 net/core/link_watch.c:67
  linkwatch_do_dev+0x3e/0x170 net/core/link_watch.c:170
  netdev_run_todo+0x461/0x1000 net/core/dev.c:10894
  rtnl_unlock net/core/rtnetlink.c:152 [inline]
  rtnl_net_unlock include/linux/rtnetlink.h:133 [inline]
  rtnl_dellink+0x760/0x8d0 net/core/rtnetlink.c:3520
  rtnetlink_rcv_msg+0x791/0xcf0 net/core/rtnetlink.c:6911
  netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2541
  netlink_unicast_kernel net/netlink/af_netlink.c:1321 [inline]
  netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1347
  netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1891
  sock_sendmsg_nosec net/socket.c:711 [inline]
  __sock_sendmsg+0x221/0x270 net/socket.c:726
  ____sys_sendmsg+0x52a/0x7e0 net/socket.c:2583
  ___sys_sendmsg net/socket.c:2637 [inline]
  __sys_sendmsg+0x269/0x350 net/socket.c:2669
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2a3cb80809
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2a3d9cd058 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f2a3cd45fa0 RCX: 00007f2a3cb80809
RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000008
RBP: 00007f2a3cbf393e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f2a3cd45fa0 R15: 00007ffd03bc65c8
 </TASK>

Allocated by task 5339:
  kasan_save_stack mm/kasan/common.c:47 [inline]
  kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
  poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
  __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:394
  kasan_kmalloc include/linux/kasan.h:260 [inline]
  __kmalloc_cache_noprof+0x243/0x390 mm/slub.c:4314
  kmalloc_noprof include/linux/slab.h:901 [inline]
  kmalloc_array_noprof include/linux/slab.h:945 [inline]
  netdev_create_hash net/core/dev.c:11870 [inline]
  netdev_init+0x10c/0x250 net/core/dev.c:11890
  ops_init+0x31e/0x590 net/core/net_namespace.c:138
  setup_net+0x287/0x9e0 net/core/net_namespace.c:362
  copy_net_ns+0x33f/0x570 net/core/net_namespace.c:500
  create_new_namespaces+0x425/0x7b0 kernel/nsproxy.c:110
  unshare_nsproxy_namespaces+0x124/0x180 kernel/nsproxy.c:228
  ksys_unshare+0x57d/0xa70 kernel/fork.c:3314
  __do_sys_unshare kernel/fork.c:3385 [inline]
  __se_sys_unshare kernel/fork.c:3383 [inline]
  __x64_sys_unshare+0x38/0x40 kernel/fork.c:3383
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 12:
  kasan_save_stack mm/kasan/common.c:47 [inline]
  kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
  kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:582
  poison_slab_object mm/kasan/common.c:247 [inline]
  __kasan_slab_free+0x59/0x70 mm/kasan/common.c:264
  kasan_slab_free include/linux/kasan.h:233 [inline]
  slab_free_hook mm/slub.c:2338 [inline]
  slab_free mm/slub.c:4598 [inline]
  kfree+0x196/0x420 mm/slub.c:4746
  netdev_exit+0x65/0xd0 net/core/dev.c:11992
  ops_exit_list net/core/net_namespace.c:172 [inline]
  cleanup_net+0x802/0xcc0 net/core/net_namespace.c:632
  process_one_work kernel/workqueue.c:3229 [inline]
  process_scheduled_works+0xa63/0x1850 kernel/workqueue.c:3310
  worker_thread+0x870/0xd30 kernel/workqueue.c:3391
  kthread+0x2f0/0x390 kernel/kthread.c:389
  ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

The buggy address belongs to the object at ffff888043eba000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 432 bytes inside of
 freed 2048-byte region [ffff888043eba000, ffff888043eba800)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x43eb8
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x4fff00000000040(head|node=1|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 04fff00000000040 ffff88801ac42000 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000080008 00000001f5000000 0000000000000000
head: 04fff00000000040 ffff88801ac42000 dead000000000122 0000000000000000
head: 0000000000000000 0000000000080008 00000001f5000000 0000000000000000
head: 04fff00000000003 ffffea00010fae01 ffffffffffffffff 0000000000000000
head: 0000000000000008 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5339, tgid 5338 (syz.0.0), ts 69674195892, free_ts 69663220888
  set_page_owner include/linux/page_owner.h:32 [inline]
  post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1556
  prep_new_page mm/page_alloc.c:1564 [inline]
  get_page_from_freelist+0x3649/0x3790 mm/page_alloc.c:3474
  __alloc_pages_noprof+0x292/0x710 mm/page_alloc.c:4751
  alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2265
  alloc_slab_page+0x6a/0x140 mm/slub.c:2408
  allocate_slab+0x5a/0x2f0 mm/slub.c:2574
  new_slab mm/slub.c:2627 [inline]
  ___slab_alloc+0xcd1/0x14b0 mm/slub.c:3815
  __slab_alloc+0x58/0xa0 mm/slub.c:3905
  __slab_alloc_node mm/slub.c:3980 [inline]
  slab_alloc_node mm/slub.c:4141 [inline]
  __do_kmalloc_node mm/slub.c:4282 [inline]
  __kmalloc_noprof+0x2e6/0x4c0 mm/slub.c:4295
  kmalloc_noprof include/linux/slab.h:905 [inline]
  sk_prot_alloc+0xe0/0x210 net/core/sock.c:2165
  sk_alloc+0x38/0x370 net/core/sock.c:2218
  __netlink_create+0x65/0x260 net/netlink/af_netlink.c:629
  __netlink_kernel_create+0x174/0x6f0 net/netlink/af_netlink.c:2015
  netlink_kernel_create include/linux/netlink.h:62 [inline]
  uevent_net_init+0xed/0x2d0 lib/kobject_uevent.c:783
  ops_init+0x31e/0x590 net/core/net_namespace.c:138
  setup_net+0x287/0x9e0 net/core/net_namespace.c:362
page last free pid 1032 tgid 1032 stack trace:
  reset_page_owner include/linux/page_owner.h:25 [inline]
  free_pages_prepare mm/page_alloc.c:1127 [inline]
  free_unref_page+0xdf9/0x1140 mm/page_alloc.c:2657
  __slab_free+0x31b/0x3d0 mm/slub.c:4509
  qlink_free mm/kasan/quarantine.c:163 [inline]
  qlist_free_all+0x9a/0x140 mm/kasan/quarantine.c:179
  kasan_quarantine_reduce+0x14f/0x170 mm/kasan/quarantine.c:286
  __kasan_slab_alloc+0x23/0x80 mm/kasan/common.c:329
  kasan_slab_alloc include/linux/kasan.h:250 [inline]
  slab_post_alloc_hook mm/slub.c:4104 [inline]
  slab_alloc_node mm/slub.c:4153 [inline]
  kmem_cache_alloc_node_noprof+0x1d9/0x380 mm/slub.c:4205
  __alloc_skb+0x1c3/0x440 net/core/skbuff.c:668
  alloc_skb include/linux/skbuff.h:1323 [inline]
  alloc_skb_with_frags+0xc3/0x820 net/core/skbuff.c:6612
  sock_alloc_send_pskb+0x91a/0xa60 net/core/sock.c:2881
  sock_alloc_send_skb include/net/sock.h:1797 [inline]
  mld_newpack+0x1c3/0xaf0 net/ipv6/mcast.c:1747
  add_grhead net/ipv6/mcast.c:1850 [inline]
  add_grec+0x1492/0x19a0 net/ipv6/mcast.c:1988
  mld_send_initial_cr+0x228/0x4b0 net/ipv6/mcast.c:2234
  ipv6_mc_dad_complete+0x88/0x490 net/ipv6/mcast.c:2245
  addrconf_dad_completed+0x712/0xcd0 net/ipv6/addrconf.c:4342
 addrconf_dad_work+0xdc2/0x16f0
  process_one_work kernel/workqueue.c:3229 [inline]
  process_scheduled_works+0xa63/0x1850 kernel/workqueue.c:3310

Memory state around the buggy address:
 ffff888043eba080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888043eba100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888043eba180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff888043eba200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888043eba280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

Fixes: 8c55facecd7a ("net: linkwatch: only report IF_OPER_LOWERLAYERDOWN if iflink is actually down")
Reported-by: syzbot+1939f24bdb783e9e43d9@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/674f3a18.050a0220.48a03.0041.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
Cc: Vladimir Oltean <vladimir.oltean@nxp.com>
---
 net/core/link_watch.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/core/link_watch.c b/net/core/link_watch.c
index ab150641142aa1545c71fc5d3b11db33c70cf437..1b4d39e38084272269a51503c217fc1e5a1326eb 100644
--- a/net/core/link_watch.c
+++ b/net/core/link_watch.c
@@ -45,9 +45,14 @@ static unsigned int default_operstate(const struct net_device *dev)
 		int iflink = dev_get_iflink(dev);
 		struct net_device *peer;
 
-		if (iflink == dev->ifindex)
+		/* If called from netdev_run_todo()/linkwatch_sync_dev(),
+		 * dev_net(dev) can be already freed, and RTNL is not held.
+		 */
+		if (dev->reg_state == NETREG_UNREGISTERED ||
+		    iflink == dev->ifindex)
 			return IF_OPER_DOWN;
 
+		ASSERT_RTNL();
 		peer = __dev_get_by_index(dev_net(dev), iflink);
 		if (!peer)
 			return IF_OPER_DOWN;
-- 
2.47.0.338.g60cca15819-goog

Re: [PATCH net] net: avoid potential UAF in default_operstate()

[Vladimir Oltean]

Hi Eric,

On Tue, Dec 03, 2024 at 05:09:33PM +0000, Eric Dumazet wrote:
> syzbot reported an UAF in default_operstate() [1]
> 
> Issue is a race between device and netns dismantles.
> 
> After calling __rtnl_unlock() from netdev_run_todo(),
> we can not assume the netns of each device is still alive.
> 
> Make sure the device is not in NETREG_UNREGISTERED state,
> and add an ASSERT_RTNL() before the call to
> __dev_get_by_index().
> 
> We might move this ASSERT_RTNL() in __dev_get_by_index()
> in the future.
> 
> [1]
> 
> BUG: KASAN: slab-use-after-free in __dev_get_by_index+0x5d/0x110 net/core/dev.c:852
> Read of size 8 at addr ffff888043eba1b0 by task syz.0.0/5339
> 
> CPU: 0 UID: 0 PID: 5339 Comm: syz.0.0 Not tainted 6.12.0-syzkaller-10296-gaaf20f870da0 #0
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
> Call Trace:
>  <TASK>
>   __dump_stack lib/dump_stack.c:94 [inline]
>   dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
>   print_address_description mm/kasan/report.c:378 [inline]
>   print_report+0x169/0x550 mm/kasan/report.c:489
>   kasan_report+0x143/0x180 mm/kasan/report.c:602
>   __dev_get_by_index+0x5d/0x110 net/core/dev.c:852
>   default_operstate net/core/link_watch.c:51 [inline]
>   rfc2863_policy+0x224/0x300 net/core/link_watch.c:67
>   linkwatch_do_dev+0x3e/0x170 net/core/link_watch.c:170
>   netdev_run_todo+0x461/0x1000 net/core/dev.c:10894
>   rtnl_unlock net/core/rtnetlink.c:152 [inline]
>   rtnl_net_unlock include/linux/rtnetlink.h:133 [inline]
>   rtnl_dellink+0x760/0x8d0 net/core/rtnetlink.c:3520
>   rtnetlink_rcv_msg+0x791/0xcf0 net/core/rtnetlink.c:6911
>   netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2541
>   netlink_unicast_kernel net/netlink/af_netlink.c:1321 [inline]
>   netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1347
>   netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1891
>   sock_sendmsg_nosec net/socket.c:711 [inline]
>   __sock_sendmsg+0x221/0x270 net/socket.c:726
>   ____sys_sendmsg+0x52a/0x7e0 net/socket.c:2583
>   ___sys_sendmsg net/socket.c:2637 [inline]
>   __sys_sendmsg+0x269/0x350 net/socket.c:2669
>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>   do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f2a3cb80809
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f2a3d9cd058 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> RAX: ffffffffffffffda RBX: 00007f2a3cd45fa0 RCX: 00007f2a3cb80809
> RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000008
> RBP: 00007f2a3cbf393e R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 0000000000000000 R14: 00007f2a3cd45fa0 R15: 00007ffd03bc65c8
>  </TASK>

In the future could you please trim irrelevant stuff from dumps like this?

> 
> Allocated by task 5339:
>   kasan_save_stack mm/kasan/common.c:47 [inline]
>   kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
>   poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
>   __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:394
>   kasan_kmalloc include/linux/kasan.h:260 [inline]
>   __kmalloc_cache_noprof+0x243/0x390 mm/slub.c:4314
>   kmalloc_noprof include/linux/slab.h:901 [inline]
>   kmalloc_array_noprof include/linux/slab.h:945 [inline]
>   netdev_create_hash net/core/dev.c:11870 [inline]
>   netdev_init+0x10c/0x250 net/core/dev.c:11890
>   ops_init+0x31e/0x590 net/core/net_namespace.c:138
>   setup_net+0x287/0x9e0 net/core/net_namespace.c:362
>   copy_net_ns+0x33f/0x570 net/core/net_namespace.c:500
>   create_new_namespaces+0x425/0x7b0 kernel/nsproxy.c:110
>   unshare_nsproxy_namespaces+0x124/0x180 kernel/nsproxy.c:228
>   ksys_unshare+0x57d/0xa70 kernel/fork.c:3314
>   __do_sys_unshare kernel/fork.c:3385 [inline]
>   __se_sys_unshare kernel/fork.c:3383 [inline]
>   __x64_sys_unshare+0x38/0x40 kernel/fork.c:3383
>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>   do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> Freed by task 12:
>   kasan_save_stack mm/kasan/common.c:47 [inline]
>   kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
>   kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:582
>   poison_slab_object mm/kasan/common.c:247 [inline]
>   __kasan_slab_free+0x59/0x70 mm/kasan/common.c:264
>   kasan_slab_free include/linux/kasan.h:233 [inline]
>   slab_free_hook mm/slub.c:2338 [inline]
>   slab_free mm/slub.c:4598 [inline]
>   kfree+0x196/0x420 mm/slub.c:4746
>   netdev_exit+0x65/0xd0 net/core/dev.c:11992
>   ops_exit_list net/core/net_namespace.c:172 [inline]
>   cleanup_net+0x802/0xcc0 net/core/net_namespace.c:632
>   process_one_work kernel/workqueue.c:3229 [inline]
>   process_scheduled_works+0xa63/0x1850 kernel/workqueue.c:3310
>   worker_thread+0x870/0xd30 kernel/workqueue.c:3391
>   kthread+0x2f0/0x390 kernel/kthread.c:389
>   ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
>   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> 
> The buggy address belongs to the object at ffff888043eba000
>  which belongs to the cache kmalloc-2k of size 2048
> The buggy address is located 432 bytes inside of
>  freed 2048-byte region [ffff888043eba000, ffff888043eba800)
> 
> The buggy address belongs to the physical page:
> page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x43eb8
> head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
> flags: 0x4fff00000000040(head|node=1|zone=1|lastcpupid=0x7ff)
> page_type: f5(slab)
> raw: 04fff00000000040 ffff88801ac42000 dead000000000122 0000000000000000
> raw: 0000000000000000 0000000000080008 00000001f5000000 0000000000000000
> head: 04fff00000000040 ffff88801ac42000 dead000000000122 0000000000000000
> head: 0000000000000000 0000000000080008 00000001f5000000 0000000000000000
> head: 04fff00000000003 ffffea00010fae01 ffffffffffffffff 0000000000000000
> head: 0000000000000008 0000000000000000 00000000ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> page_owner tracks the page as allocated
> page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5339, tgid 5338 (syz.0.0), ts 69674195892, free_ts 69663220888
>   set_page_owner include/linux/page_owner.h:32 [inline]
>   post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1556
>   prep_new_page mm/page_alloc.c:1564 [inline]
>   get_page_from_freelist+0x3649/0x3790 mm/page_alloc.c:3474
>   __alloc_pages_noprof+0x292/0x710 mm/page_alloc.c:4751
>   alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2265
>   alloc_slab_page+0x6a/0x140 mm/slub.c:2408
>   allocate_slab+0x5a/0x2f0 mm/slub.c:2574
>   new_slab mm/slub.c:2627 [inline]
>   ___slab_alloc+0xcd1/0x14b0 mm/slub.c:3815
>   __slab_alloc+0x58/0xa0 mm/slub.c:3905
>   __slab_alloc_node mm/slub.c:3980 [inline]
>   slab_alloc_node mm/slub.c:4141 [inline]
>   __do_kmalloc_node mm/slub.c:4282 [inline]
>   __kmalloc_noprof+0x2e6/0x4c0 mm/slub.c:4295
>   kmalloc_noprof include/linux/slab.h:905 [inline]
>   sk_prot_alloc+0xe0/0x210 net/core/sock.c:2165
>   sk_alloc+0x38/0x370 net/core/sock.c:2218
>   __netlink_create+0x65/0x260 net/netlink/af_netlink.c:629
>   __netlink_kernel_create+0x174/0x6f0 net/netlink/af_netlink.c:2015
>   netlink_kernel_create include/linux/netlink.h:62 [inline]
>   uevent_net_init+0xed/0x2d0 lib/kobject_uevent.c:783
>   ops_init+0x31e/0x590 net/core/net_namespace.c:138
>   setup_net+0x287/0x9e0 net/core/net_namespace.c:362
> page last free pid 1032 tgid 1032 stack trace:
>   reset_page_owner include/linux/page_owner.h:25 [inline]
>   free_pages_prepare mm/page_alloc.c:1127 [inline]
>   free_unref_page+0xdf9/0x1140 mm/page_alloc.c:2657
>   __slab_free+0x31b/0x3d0 mm/slub.c:4509
>   qlink_free mm/kasan/quarantine.c:163 [inline]
>   qlist_free_all+0x9a/0x140 mm/kasan/quarantine.c:179
>   kasan_quarantine_reduce+0x14f/0x170 mm/kasan/quarantine.c:286
>   __kasan_slab_alloc+0x23/0x80 mm/kasan/common.c:329
>   kasan_slab_alloc include/linux/kasan.h:250 [inline]
>   slab_post_alloc_hook mm/slub.c:4104 [inline]
>   slab_alloc_node mm/slub.c:4153 [inline]
>   kmem_cache_alloc_node_noprof+0x1d9/0x380 mm/slub.c:4205
>   __alloc_skb+0x1c3/0x440 net/core/skbuff.c:668
>   alloc_skb include/linux/skbuff.h:1323 [inline]
>   alloc_skb_with_frags+0xc3/0x820 net/core/skbuff.c:6612
>   sock_alloc_send_pskb+0x91a/0xa60 net/core/sock.c:2881
>   sock_alloc_send_skb include/net/sock.h:1797 [inline]
>   mld_newpack+0x1c3/0xaf0 net/ipv6/mcast.c:1747
>   add_grhead net/ipv6/mcast.c:1850 [inline]
>   add_grec+0x1492/0x19a0 net/ipv6/mcast.c:1988
>   mld_send_initial_cr+0x228/0x4b0 net/ipv6/mcast.c:2234
>   ipv6_mc_dad_complete+0x88/0x490 net/ipv6/mcast.c:2245
>   addrconf_dad_completed+0x712/0xcd0 net/ipv6/addrconf.c:4342
>  addrconf_dad_work+0xdc2/0x16f0
>   process_one_work kernel/workqueue.c:3229 [inline]
>   process_scheduled_works+0xa63/0x1850 kernel/workqueue.c:3310
> 
> Memory state around the buggy address:
>  ffff888043eba080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff888043eba100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >ffff888043eba180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                      ^
>  ffff888043eba200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff888043eba280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> 
> Fixes: 8c55facecd7a ("net: linkwatch: only report IF_OPER_LOWERLAYERDOWN if iflink is actually down")
> Reported-by: syzbot+1939f24bdb783e9e43d9@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/netdev/674f3a18.050a0220.48a03.0041.GAE@google.com/T/#u
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---
> Cc: Vladimir Oltean <vladimir.oltean@nxp.com>
> ---
>  net/core/link_watch.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/net/core/link_watch.c b/net/core/link_watch.c
> index ab150641142aa1545c71fc5d3b11db33c70cf437..1b4d39e38084272269a51503c217fc1e5a1326eb 100644
> --- a/net/core/link_watch.c
> +++ b/net/core/link_watch.c
> @@ -45,9 +45,14 @@ static unsigned int default_operstate(const struct net_device *dev)
>  		int iflink = dev_get_iflink(dev);
>  		struct net_device *peer;
>  
> -		if (iflink == dev->ifindex)
> +		/* If called from netdev_run_todo()/linkwatch_sync_dev(),
> +		 * dev_net(dev) can be already freed, and RTNL is not held.
> +		 */
> +		if (dev->reg_state == NETREG_UNREGISTERED ||
> +		    iflink == dev->ifindex)
>  			return IF_OPER_DOWN;
>  
> +		ASSERT_RTNL();
>  		peer = __dev_get_by_index(dev_net(dev), iflink);
>  		if (!peer)
>  			return IF_OPER_DOWN;
> -- 
> 2.47.0.338.g60cca15819-goog
>

Thanks for submitting a patch, the issue makes sense.

Question: is the rtnl_mutex actually held in the problematic case though?
The netdev_run_todo() call path is:

	__rtnl_unlock();						<- unlocks

	/* Wait for rcu callbacks to finish before next phase */
	if (!list_empty(&list))
		rcu_barrier();

	list_for_each_entry_safe(dev, tmp, &list, todo_list) {
		if (unlikely(dev->reg_state != NETREG_UNREGISTERING)) {
			netdev_WARN(dev, "run_todo but not unregistering\n");
			list_del(&dev->todo_list);
			continue;
		}

		WRITE_ONCE(dev->reg_state, NETREG_UNREGISTERED);
		linkwatch_sync_dev(dev);				<- asserts
	}

And on the same note: does linkwatch not have a chance to run also,
concurrently with us, in this timeframe? Could we not catch the
dev->reg_state in NETREG_UNREGISTERING?

Re: [PATCH net] net: avoid potential UAF in default_operstate()

[Eric Dumazet]

On Tue, Dec 3, 2024 at 6:37 PM Vladimir Oltean <vladimir.oltean@nxp.com> wrote:
>
> Hi Eric,
>
> On Tue, Dec 03, 2024 at 05:09:33PM +0000, Eric Dumazet wrote:
> > syzbot reported an UAF in default_operstate() [1]
> >
> > Issue is a race between device and netns dismantles.
> >
> > After calling __rtnl_unlock() from netdev_run_todo(),
> > we can not assume the netns of each device is still alive.
> >
> > Make sure the device is not in NETREG_UNREGISTERED state,
> > and add an ASSERT_RTNL() before the call to
> > __dev_get_by_index().
> >
> > We might move this ASSERT_RTNL() in __dev_get_by_index()
> > in the future.
> >
> > [1]
> >
> > BUG: KASAN: slab-use-after-free in __dev_get_by_index+0x5d/0x110 net/core/dev.c:852
> > Read of size 8 at addr ffff888043eba1b0 by task syz.0.0/5339
> >
> > CPU: 0 UID: 0 PID: 5339 Comm: syz.0.0 Not tainted 6.12.0-syzkaller-10296-gaaf20f870da0 #0
> > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
> > Call Trace:
> >  <TASK>
> >   __dump_stack lib/dump_stack.c:94 [inline]
> >   dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
> >   print_address_description mm/kasan/report.c:378 [inline]
> >   print_report+0x169/0x550 mm/kasan/report.c:489
> >   kasan_report+0x143/0x180 mm/kasan/report.c:602
> >   __dev_get_by_index+0x5d/0x110 net/core/dev.c:852
> >   default_operstate net/core/link_watch.c:51 [inline]
> >   rfc2863_policy+0x224/0x300 net/core/link_watch.c:67
> >   linkwatch_do_dev+0x3e/0x170 net/core/link_watch.c:170
> >   netdev_run_todo+0x461/0x1000 net/core/dev.c:10894
> >   rtnl_unlock net/core/rtnetlink.c:152 [inline]
> >   rtnl_net_unlock include/linux/rtnetlink.h:133 [inline]
> >   rtnl_dellink+0x760/0x8d0 net/core/rtnetlink.c:3520
> >   rtnetlink_rcv_msg+0x791/0xcf0 net/core/rtnetlink.c:6911
> >   netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2541
> >   netlink_unicast_kernel net/netlink/af_netlink.c:1321 [inline]
> >   netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1347
> >   netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1891
> >   sock_sendmsg_nosec net/socket.c:711 [inline]
> >   __sock_sendmsg+0x221/0x270 net/socket.c:726
> >   ____sys_sendmsg+0x52a/0x7e0 net/socket.c:2583
> >   ___sys_sendmsg net/socket.c:2637 [inline]
> >   __sys_sendmsg+0x269/0x350 net/socket.c:2669
> >   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> >   do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
> >  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > RIP: 0033:0x7f2a3cb80809
> > Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
> > RSP: 002b:00007f2a3d9cd058 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> > RAX: ffffffffffffffda RBX: 00007f2a3cd45fa0 RCX: 00007f2a3cb80809
> > RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000008
> > RBP: 00007f2a3cbf393e R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> > R13: 0000000000000000 R14: 00007f2a3cd45fa0 R15: 00007ffd03bc65c8
> >  </TASK>
>
> In the future could you please trim irrelevant stuff from dumps like this?

I prefer the full output, it can be very useful. It is relevant to me at least.

>
> >
> > Allocated by task 5339:
> >   kasan_save_stack mm/kasan/common.c:47 [inline]
> >   kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
> >   poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
> >   __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:394
> >   kasan_kmalloc include/linux/kasan.h:260 [inline]
> >   __kmalloc_cache_noprof+0x243/0x390 mm/slub.c:4314
> >   kmalloc_noprof include/linux/slab.h:901 [inline]
> >   kmalloc_array_noprof include/linux/slab.h:945 [inline]
> >   netdev_create_hash net/core/dev.c:11870 [inline]
> >   netdev_init+0x10c/0x250 net/core/dev.c:11890
> >   ops_init+0x31e/0x590 net/core/net_namespace.c:138
> >   setup_net+0x287/0x9e0 net/core/net_namespace.c:362
> >   copy_net_ns+0x33f/0x570 net/core/net_namespace.c:500
> >   create_new_namespaces+0x425/0x7b0 kernel/nsproxy.c:110
> >   unshare_nsproxy_namespaces+0x124/0x180 kernel/nsproxy.c:228
> >   ksys_unshare+0x57d/0xa70 kernel/fork.c:3314
> >   __do_sys_unshare kernel/fork.c:3385 [inline]
> >   __se_sys_unshare kernel/fork.c:3383 [inline]
> >   __x64_sys_unshare+0x38/0x40 kernel/fork.c:3383
> >   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> >   do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
> >  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> >
> > Freed by task 12:
> >   kasan_save_stack mm/kasan/common.c:47 [inline]
> >   kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
> >   kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:582
> >   poison_slab_object mm/kasan/common.c:247 [inline]
> >   __kasan_slab_free+0x59/0x70 mm/kasan/common.c:264
> >   kasan_slab_free include/linux/kasan.h:233 [inline]
> >   slab_free_hook mm/slub.c:2338 [inline]
> >   slab_free mm/slub.c:4598 [inline]
> >   kfree+0x196/0x420 mm/slub.c:4746
> >   netdev_exit+0x65/0xd0 net/core/dev.c:11992
> >   ops_exit_list net/core/net_namespace.c:172 [inline]
> >   cleanup_net+0x802/0xcc0 net/core/net_namespace.c:632
> >   process_one_work kernel/workqueue.c:3229 [inline]
> >   process_scheduled_works+0xa63/0x1850 kernel/workqueue.c:3310
> >   worker_thread+0x870/0xd30 kernel/workqueue.c:3391
> >   kthread+0x2f0/0x390 kernel/kthread.c:389
> >   ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
> >   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> >
> > The buggy address belongs to the object at ffff888043eba000
> >  which belongs to the cache kmalloc-2k of size 2048
> > The buggy address is located 432 bytes inside of
> >  freed 2048-byte region [ffff888043eba000, ffff888043eba800)
> >
> > The buggy address belongs to the physical page:
> > page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x43eb8
> > head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
> > flags: 0x4fff00000000040(head|node=1|zone=1|lastcpupid=0x7ff)
> > page_type: f5(slab)
> > raw: 04fff00000000040 ffff88801ac42000 dead000000000122 0000000000000000
> > raw: 0000000000000000 0000000000080008 00000001f5000000 0000000000000000
> > head: 04fff00000000040 ffff88801ac42000 dead000000000122 0000000000000000
> > head: 0000000000000000 0000000000080008 00000001f5000000 0000000000000000
> > head: 04fff00000000003 ffffea00010fae01 ffffffffffffffff 0000000000000000
> > head: 0000000000000008 0000000000000000 00000000ffffffff 0000000000000000
> > page dumped because: kasan: bad access detected
> > page_owner tracks the page as allocated
> > page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5339, tgid 5338 (syz.0.0), ts 69674195892, free_ts 69663220888
> >   set_page_owner include/linux/page_owner.h:32 [inline]
> >   post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1556
> >   prep_new_page mm/page_alloc.c:1564 [inline]
> >   get_page_from_freelist+0x3649/0x3790 mm/page_alloc.c:3474
> >   __alloc_pages_noprof+0x292/0x710 mm/page_alloc.c:4751
> >   alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2265
> >   alloc_slab_page+0x6a/0x140 mm/slub.c:2408
> >   allocate_slab+0x5a/0x2f0 mm/slub.c:2574
> >   new_slab mm/slub.c:2627 [inline]
> >   ___slab_alloc+0xcd1/0x14b0 mm/slub.c:3815
> >   __slab_alloc+0x58/0xa0 mm/slub.c:3905
> >   __slab_alloc_node mm/slub.c:3980 [inline]
> >   slab_alloc_node mm/slub.c:4141 [inline]
> >   __do_kmalloc_node mm/slub.c:4282 [inline]
> >   __kmalloc_noprof+0x2e6/0x4c0 mm/slub.c:4295
> >   kmalloc_noprof include/linux/slab.h:905 [inline]
> >   sk_prot_alloc+0xe0/0x210 net/core/sock.c:2165
> >   sk_alloc+0x38/0x370 net/core/sock.c:2218
> >   __netlink_create+0x65/0x260 net/netlink/af_netlink.c:629
> >   __netlink_kernel_create+0x174/0x6f0 net/netlink/af_netlink.c:2015
> >   netlink_kernel_create include/linux/netlink.h:62 [inline]
> >   uevent_net_init+0xed/0x2d0 lib/kobject_uevent.c:783
> >   ops_init+0x31e/0x590 net/core/net_namespace.c:138
> >   setup_net+0x287/0x9e0 net/core/net_namespace.c:362
> > page last free pid 1032 tgid 1032 stack trace:
> >   reset_page_owner include/linux/page_owner.h:25 [inline]
> >   free_pages_prepare mm/page_alloc.c:1127 [inline]
> >   free_unref_page+0xdf9/0x1140 mm/page_alloc.c:2657
> >   __slab_free+0x31b/0x3d0 mm/slub.c:4509
> >   qlink_free mm/kasan/quarantine.c:163 [inline]
> >   qlist_free_all+0x9a/0x140 mm/kasan/quarantine.c:179
> >   kasan_quarantine_reduce+0x14f/0x170 mm/kasan/quarantine.c:286
> >   __kasan_slab_alloc+0x23/0x80 mm/kasan/common.c:329
> >   kasan_slab_alloc include/linux/kasan.h:250 [inline]
> >   slab_post_alloc_hook mm/slub.c:4104 [inline]
> >   slab_alloc_node mm/slub.c:4153 [inline]
> >   kmem_cache_alloc_node_noprof+0x1d9/0x380 mm/slub.c:4205
> >   __alloc_skb+0x1c3/0x440 net/core/skbuff.c:668
> >   alloc_skb include/linux/skbuff.h:1323 [inline]
> >   alloc_skb_with_frags+0xc3/0x820 net/core/skbuff.c:6612
> >   sock_alloc_send_pskb+0x91a/0xa60 net/core/sock.c:2881
> >   sock_alloc_send_skb include/net/sock.h:1797 [inline]
> >   mld_newpack+0x1c3/0xaf0 net/ipv6/mcast.c:1747
> >   add_grhead net/ipv6/mcast.c:1850 [inline]
> >   add_grec+0x1492/0x19a0 net/ipv6/mcast.c:1988
> >   mld_send_initial_cr+0x228/0x4b0 net/ipv6/mcast.c:2234
> >   ipv6_mc_dad_complete+0x88/0x490 net/ipv6/mcast.c:2245
> >   addrconf_dad_completed+0x712/0xcd0 net/ipv6/addrconf.c:4342
> >  addrconf_dad_work+0xdc2/0x16f0
> >   process_one_work kernel/workqueue.c:3229 [inline]
> >   process_scheduled_works+0xa63/0x1850 kernel/workqueue.c:3310
> >
> > Memory state around the buggy address:
> >  ffff888043eba080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >  ffff888043eba100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > >ffff888043eba180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >                                      ^
> >  ffff888043eba200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >  ffff888043eba280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >
> > Fixes: 8c55facecd7a ("net: linkwatch: only report IF_OPER_LOWERLAYERDOWN if iflink is actually down")
> > Reported-by: syzbot+1939f24bdb783e9e43d9@syzkaller.appspotmail.com
> > Closes: https://lore.kernel.org/netdev/674f3a18.050a0220.48a03.0041.GAE@google.com/T/#u
> > Signed-off-by: Eric Dumazet <edumazet@google.com>
> > ---
> > Cc: Vladimir Oltean <vladimir.oltean@nxp.com>
> > ---
> >  net/core/link_watch.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/core/link_watch.c b/net/core/link_watch.c
> > index ab150641142aa1545c71fc5d3b11db33c70cf437..1b4d39e38084272269a51503c217fc1e5a1326eb 100644
> > --- a/net/core/link_watch.c
> > +++ b/net/core/link_watch.c
> > @@ -45,9 +45,14 @@ static unsigned int default_operstate(const struct net_device *dev)
> >               int iflink = dev_get_iflink(dev);
> >               struct net_device *peer;
> >
> > -             if (iflink == dev->ifindex)
> > +             /* If called from netdev_run_todo()/linkwatch_sync_dev(),
> > +              * dev_net(dev) can be already freed, and RTNL is not held.
> > +              */
> > +             if (dev->reg_state == NETREG_UNREGISTERED ||
> > +                 iflink == dev->ifindex)
> >                       return IF_OPER_DOWN;
> >
> > +             ASSERT_RTNL();
> >               peer = __dev_get_by_index(dev_net(dev), iflink);
> >               if (!peer)
> >                       return IF_OPER_DOWN;
> > --
> > 2.47.0.338.g60cca15819-goog
> >
>
> Thanks for submitting a patch, the issue makes sense.
>
> Question: is the rtnl_mutex actually held in the problematic case though?
> The netdev_run_todo() call path is:

As explained in the comment, RTNL is not held in this case :

 /* If called from netdev_run_todo()/linkwatch_sync_dev(),
 * dev_net(dev) can be already freed, and RTNL is not held.
 */

In the future, we might change default_operstate() to use dev_get_by_index_rcu()
and not rely on RTNL anymore, but after this patch, the ASSERT_RTNL() is fine.


>
>         __rtnl_unlock();                                                <- unlocks
>
>         /* Wait for rcu callbacks to finish before next phase */
>         if (!list_empty(&list))
>                 rcu_barrier();
>
>         list_for_each_entry_safe(dev, tmp, &list, todo_list) {
>                 if (unlikely(dev->reg_state != NETREG_UNREGISTERING)) {
>                         netdev_WARN(dev, "run_todo but not unregistering\n");
>                         list_del(&dev->todo_list);
>                         continue;
>                 }
>
>                 WRITE_ONCE(dev->reg_state, NETREG_UNREGISTERED);

// reg_state is set to NETREG_UNREGISTERING

>                 linkwatch_sync_dev(dev);                                <- asserts
>         }
>
> And on the same note: does linkwatch not have a chance to run also,
> concurrently with us, in this timeframe? Could we not catch the
> dev->reg_state in NETREG_UNREGISTERING?

I guess we can add a READ_ONCE() on many dev->reg_state reads.

The race should not matter for linkwatch, if the device is going away.

Re: [PATCH net] net: avoid potential UAF in default_operstate()

[Vladimir Oltean]

On Tue, Dec 03, 2024 at 06:56:09PM +0100, Eric Dumazet wrote:
> On Tue, Dec 3, 2024 at 6:37 PM Vladimir Oltean <vladimir.oltean@nxp.com> wrote:
> >
> > Hi Eric,
> >
> > On Tue, Dec 03, 2024 at 05:09:33PM +0000, Eric Dumazet wrote:
> > > syzbot reported an UAF in default_operstate() [1]
> > >
> > > Issue is a race between device and netns dismantles.
> > >
> > > After calling __rtnl_unlock() from netdev_run_todo(),
> > > we can not assume the netns of each device is still alive.
> > >
> > > Make sure the device is not in NETREG_UNREGISTERED state,
> > > and add an ASSERT_RTNL() before the call to
> > > __dev_get_by_index().
> > >
> > > We might move this ASSERT_RTNL() in __dev_get_by_index()
> > > in the future.
> > >
> > > [1]
> > >
> > > BUG: KASAN: slab-use-after-free in __dev_get_by_index+0x5d/0x110 net/core/dev.c:852
> > > Read of size 8 at addr ffff888043eba1b0 by task syz.0.0/5339
> > >
> > > CPU: 0 UID: 0 PID: 5339 Comm: syz.0.0 Not tainted 6.12.0-syzkaller-10296-gaaf20f870da0 #0
> > > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
> > > Call Trace:
> > >  <TASK>
> > >   __dump_stack lib/dump_stack.c:94 [inline]
> > >   dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
> > >   print_address_description mm/kasan/report.c:378 [inline]
> > >   print_report+0x169/0x550 mm/kasan/report.c:489
> > >   kasan_report+0x143/0x180 mm/kasan/report.c:602
> > >   __dev_get_by_index+0x5d/0x110 net/core/dev.c:852
> > >   default_operstate net/core/link_watch.c:51 [inline]
> > >   rfc2863_policy+0x224/0x300 net/core/link_watch.c:67
> > >   linkwatch_do_dev+0x3e/0x170 net/core/link_watch.c:170
> > >   netdev_run_todo+0x461/0x1000 net/core/dev.c:10894
> > >   rtnl_unlock net/core/rtnetlink.c:152 [inline]
> > >   rtnl_net_unlock include/linux/rtnetlink.h:133 [inline]
> > >   rtnl_dellink+0x760/0x8d0 net/core/rtnetlink.c:3520
> > >   rtnetlink_rcv_msg+0x791/0xcf0 net/core/rtnetlink.c:6911
> > >   netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2541
> > >   netlink_unicast_kernel net/netlink/af_netlink.c:1321 [inline]
> > >   netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1347
> > >   netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1891
> > >   sock_sendmsg_nosec net/socket.c:711 [inline]
> > >   __sock_sendmsg+0x221/0x270 net/socket.c:726
> > >   ____sys_sendmsg+0x52a/0x7e0 net/socket.c:2583
> > >   ___sys_sendmsg net/socket.c:2637 [inline]
> > >   __sys_sendmsg+0x269/0x350 net/socket.c:2669
> > >   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> > >   do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
> > >  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > > RIP: 0033:0x7f2a3cb80809
> > > Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
> > > RSP: 002b:00007f2a3d9cd058 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> > > RAX: ffffffffffffffda RBX: 00007f2a3cd45fa0 RCX: 00007f2a3cb80809
> > > RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000008
> > > RBP: 00007f2a3cbf393e R08: 0000000000000000 R09: 0000000000000000
> > > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> > > R13: 0000000000000000 R14: 00007f2a3cd45fa0 R15: 00007ffd03bc65c8
> > >  </TASK>
> >
> > In the future could you please trim irrelevant stuff from dumps like this?
> 
> I prefer the full output, it can be very useful. It is relevant to me at least.

I mean the kasan, dump_stack and mm portion from the stack traces,
as well as the register dump, are pretty much irrelevant. They make
navigating the useful portion of the kasan splat more difficult.

> > > Allocated by task 5339:
> > >   kasan_save_stack mm/kasan/common.c:47 [inline]
> > >   kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
> > >   poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
> > >   __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:394
> > >   kasan_kmalloc include/linux/kasan.h:260 [inline]
> > >   __kmalloc_cache_noprof+0x243/0x390 mm/slub.c:4314
> > >   kmalloc_noprof include/linux/slab.h:901 [inline]
> > >   kmalloc_array_noprof include/linux/slab.h:945 [inline]
> > >   netdev_create_hash net/core/dev.c:11870 [inline]
> > >   netdev_init+0x10c/0x250 net/core/dev.c:11890
> > >   ops_init+0x31e/0x590 net/core/net_namespace.c:138
> > >   setup_net+0x287/0x9e0 net/core/net_namespace.c:362
> > >   copy_net_ns+0x33f/0x570 net/core/net_namespace.c:500
> > >   create_new_namespaces+0x425/0x7b0 kernel/nsproxy.c:110
> > >   unshare_nsproxy_namespaces+0x124/0x180 kernel/nsproxy.c:228
> > >   ksys_unshare+0x57d/0xa70 kernel/fork.c:3314
> > >   __do_sys_unshare kernel/fork.c:3385 [inline]
> > >   __se_sys_unshare kernel/fork.c:3383 [inline]
> > >   __x64_sys_unshare+0x38/0x40 kernel/fork.c:3383
> > >   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> > >   do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
> > >  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > >
> > > Freed by task 12:
> > >   kasan_save_stack mm/kasan/common.c:47 [inline]
> > >   kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
> > >   kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:582
> > >   poison_slab_object mm/kasan/common.c:247 [inline]
> > >   __kasan_slab_free+0x59/0x70 mm/kasan/common.c:264
> > >   kasan_slab_free include/linux/kasan.h:233 [inline]
> > >   slab_free_hook mm/slub.c:2338 [inline]
> > >   slab_free mm/slub.c:4598 [inline]
> > >   kfree+0x196/0x420 mm/slub.c:4746
> > >   netdev_exit+0x65/0xd0 net/core/dev.c:11992
> > >   ops_exit_list net/core/net_namespace.c:172 [inline]
> > >   cleanup_net+0x802/0xcc0 net/core/net_namespace.c:632

Where is __put_net() called from? The timeline is not clear to me.

> > >   process_one_work kernel/workqueue.c:3229 [inline]
> > >   process_scheduled_works+0xa63/0x1850 kernel/workqueue.c:3310
> > >   worker_thread+0x870/0xd30 kernel/workqueue.c:3391
> > >   kthread+0x2f0/0x390 kernel/kthread.c:389
> > >   ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
> > >   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > >
> > > The buggy address belongs to the object at ffff888043eba000
> > >  which belongs to the cache kmalloc-2k of size 2048
> > > The buggy address is located 432 bytes inside of
> > >  freed 2048-byte region [ffff888043eba000, ffff888043eba800)
> > >
> > > The buggy address belongs to the physical page:
> > > page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x43eb8
> > > head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
> > > flags: 0x4fff00000000040(head|node=1|zone=1|lastcpupid=0x7ff)
> > > page_type: f5(slab)
> > > raw: 04fff00000000040 ffff88801ac42000 dead000000000122 0000000000000000
> > > raw: 0000000000000000 0000000000080008 00000001f5000000 0000000000000000
> > > head: 04fff00000000040 ffff88801ac42000 dead000000000122 0000000000000000
> > > head: 0000000000000000 0000000000080008 00000001f5000000 0000000000000000
> > > head: 04fff00000000003 ffffea00010fae01 ffffffffffffffff 0000000000000000
> > > head: 0000000000000008 0000000000000000 00000000ffffffff 0000000000000000
> > > page dumped because: kasan: bad access detected
> > > page_owner tracks the page as allocated
> > > page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5339, tgid 5338 (syz.0.0), ts 69674195892, free_ts 69663220888
> > >   set_page_owner include/linux/page_owner.h:32 [inline]
> > >   post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1556
> > >   prep_new_page mm/page_alloc.c:1564 [inline]
> > >   get_page_from_freelist+0x3649/0x3790 mm/page_alloc.c:3474
> > >   __alloc_pages_noprof+0x292/0x710 mm/page_alloc.c:4751
> > >   alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2265
> > >   alloc_slab_page+0x6a/0x140 mm/slub.c:2408
> > >   allocate_slab+0x5a/0x2f0 mm/slub.c:2574
> > >   new_slab mm/slub.c:2627 [inline]
> > >   ___slab_alloc+0xcd1/0x14b0 mm/slub.c:3815
> > >   __slab_alloc+0x58/0xa0 mm/slub.c:3905
> > >   __slab_alloc_node mm/slub.c:3980 [inline]
> > >   slab_alloc_node mm/slub.c:4141 [inline]
> > >   __do_kmalloc_node mm/slub.c:4282 [inline]
> > >   __kmalloc_noprof+0x2e6/0x4c0 mm/slub.c:4295
> > >   kmalloc_noprof include/linux/slab.h:905 [inline]
> > >   sk_prot_alloc+0xe0/0x210 net/core/sock.c:2165
> > >   sk_alloc+0x38/0x370 net/core/sock.c:2218
> > >   __netlink_create+0x65/0x260 net/netlink/af_netlink.c:629
> > >   __netlink_kernel_create+0x174/0x6f0 net/netlink/af_netlink.c:2015
> > >   netlink_kernel_create include/linux/netlink.h:62 [inline]
> > >   uevent_net_init+0xed/0x2d0 lib/kobject_uevent.c:783
> > >   ops_init+0x31e/0x590 net/core/net_namespace.c:138
> > >   setup_net+0x287/0x9e0 net/core/net_namespace.c:362
> > > page last free pid 1032 tgid 1032 stack trace:
> > >   reset_page_owner include/linux/page_owner.h:25 [inline]
> > >   free_pages_prepare mm/page_alloc.c:1127 [inline]
> > >   free_unref_page+0xdf9/0x1140 mm/page_alloc.c:2657
> > >   __slab_free+0x31b/0x3d0 mm/slub.c:4509
> > >   qlink_free mm/kasan/quarantine.c:163 [inline]
> > >   qlist_free_all+0x9a/0x140 mm/kasan/quarantine.c:179
> > >   kasan_quarantine_reduce+0x14f/0x170 mm/kasan/quarantine.c:286
> > >   __kasan_slab_alloc+0x23/0x80 mm/kasan/common.c:329
> > >   kasan_slab_alloc include/linux/kasan.h:250 [inline]
> > >   slab_post_alloc_hook mm/slub.c:4104 [inline]
> > >   slab_alloc_node mm/slub.c:4153 [inline]
> > >   kmem_cache_alloc_node_noprof+0x1d9/0x380 mm/slub.c:4205
> > >   __alloc_skb+0x1c3/0x440 net/core/skbuff.c:668
> > >   alloc_skb include/linux/skbuff.h:1323 [inline]
> > >   alloc_skb_with_frags+0xc3/0x820 net/core/skbuff.c:6612
> > >   sock_alloc_send_pskb+0x91a/0xa60 net/core/sock.c:2881
> > >   sock_alloc_send_skb include/net/sock.h:1797 [inline]
> > >   mld_newpack+0x1c3/0xaf0 net/ipv6/mcast.c:1747
> > >   add_grhead net/ipv6/mcast.c:1850 [inline]
> > >   add_grec+0x1492/0x19a0 net/ipv6/mcast.c:1988
> > >   mld_send_initial_cr+0x228/0x4b0 net/ipv6/mcast.c:2234
> > >   ipv6_mc_dad_complete+0x88/0x490 net/ipv6/mcast.c:2245
> > >   addrconf_dad_completed+0x712/0xcd0 net/ipv6/addrconf.c:4342
> > >  addrconf_dad_work+0xdc2/0x16f0
> > >   process_one_work kernel/workqueue.c:3229 [inline]
> > >   process_scheduled_works+0xa63/0x1850 kernel/workqueue.c:3310
> > >
> > > Memory state around the buggy address:
> > >  ffff888043eba080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > >  ffff888043eba100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > >ffff888043eba180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > >                                      ^
> > >  ffff888043eba200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > >  ffff888043eba280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > >
> > > Fixes: 8c55facecd7a ("net: linkwatch: only report IF_OPER_LOWERLAYERDOWN if iflink is actually down")
> > > Reported-by: syzbot+1939f24bdb783e9e43d9@syzkaller.appspotmail.com
> > > Closes: https://lore.kernel.org/netdev/674f3a18.050a0220.48a03.0041.GAE@google.com/T/#u
> > > Signed-off-by: Eric Dumazet <edumazet@google.com>
> > > ---
> > > Cc: Vladimir Oltean <vladimir.oltean@nxp.com>
> > > ---
> > >  net/core/link_watch.c | 7 ++++++-
> > >  1 file changed, 6 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/net/core/link_watch.c b/net/core/link_watch.c
> > > index ab150641142aa1545c71fc5d3b11db33c70cf437..1b4d39e38084272269a51503c217fc1e5a1326eb 100644
> > > --- a/net/core/link_watch.c
> > > +++ b/net/core/link_watch.c
> > > @@ -45,9 +45,14 @@ static unsigned int default_operstate(const struct net_device *dev)
> > >               int iflink = dev_get_iflink(dev);
> > >               struct net_device *peer;
> > >
> > > -             if (iflink == dev->ifindex)
> > > +             /* If called from netdev_run_todo()/linkwatch_sync_dev(),
> > > +              * dev_net(dev) can be already freed, and RTNL is not held.
> > > +              */
> > > +             if (dev->reg_state == NETREG_UNREGISTERED ||
> > > +                 iflink == dev->ifindex)
> > >                       return IF_OPER_DOWN;
> > >
> > > +             ASSERT_RTNL();
> > >               peer = __dev_get_by_index(dev_net(dev), iflink);
> > >               if (!peer)
> > >                       return IF_OPER_DOWN;
> > > --
> > > 2.47.0.338.g60cca15819-goog
> > >
> >
> > Thanks for submitting a patch, the issue makes sense.
> >
> > Question: is the rtnl_mutex actually held in the problematic case though?
> > The netdev_run_todo() call path is:
> 
> As explained in the comment, RTNL is not held in this case :
> 
>  /* If called from netdev_run_todo()/linkwatch_sync_dev(),
>  * dev_net(dev) can be already freed, and RTNL is not held.
>  */
> 
> In the future, we might change default_operstate() to use dev_get_by_index_rcu()
> and not rely on RTNL anymore, but after this patch, the ASSERT_RTNL() is fine.

Ah, ASSERT_RTNL() is only done if the reg_state is not NETREG_UNREGISTERED.
I misinterpreted the order of operations and thought it is asserted unconditionally.
My bad.

> >
> >         __rtnl_unlock();                                                <- unlocks
> >
> >         /* Wait for rcu callbacks to finish before next phase */
> >         if (!list_empty(&list))
> >                 rcu_barrier();
> >
> >         list_for_each_entry_safe(dev, tmp, &list, todo_list) {
> >                 if (unlikely(dev->reg_state != NETREG_UNREGISTERING)) {
> >                         netdev_WARN(dev, "run_todo but not unregistering\n");
> >                         list_del(&dev->todo_list);
> >                         continue;
> >                 }
> >
> >                 WRITE_ONCE(dev->reg_state, NETREG_UNREGISTERED);
> 
> // reg_state is set to NETREG_UNREGISTERING
> 
> >                 linkwatch_sync_dev(dev);                                <- asserts
> >         }
> >
> > And on the same note: does linkwatch not have a chance to run also,
> > concurrently with us, in this timeframe? Could we not catch the
> > dev->reg_state in NETREG_UNREGISTERING?
> 
> I guess we can add a READ_ONCE() on many dev->reg_state reads.
> 
> The race should not matter for linkwatch, if the device is going away.

I meant: linkwatch runs periodically, via linkwatch_event(). Isn't there
a chance that linkwatch_event() can run once, immediately after
__rtnl_unlock() in netdev_run_todo(), while the netdev is in the
NETREG_UNREGISTERING state? Won't that create problems for __dev_get_by_index()
too? I guess it depends on when the netns is torn down, which I couldn't find.

Re: [PATCH net] net: avoid potential UAF in default_operstate()

[Eric Dumazet]

On Wed, Dec 4, 2024 at 12:41 PM Vladimir Oltean <vladimir.oltean@nxp.com> wrote:
>
> I meant: linkwatch runs periodically, via linkwatch_event(). Isn't there
> a chance that linkwatch_event() can run once, immediately after
> __rtnl_unlock() in netdev_run_todo(), while the netdev is in the
> NETREG_UNREGISTERING state? Won't that create problems for __dev_get_by_index()
> too? I guess it depends on when the netns is torn down, which I couldn't find.

I think lweventlist_lock and dev->link_watch_list are supposed to
synchronize things.

linkwatch_sync_dev() only calls linkwatch_do_dev() if the device was
atomically unlinked from lweventlist

Re: [PATCH net] net: avoid potential UAF in default_operstate()

[Vladimir Oltean]

On Wed, Dec 04, 2024 at 12:46:11PM +0100, Eric Dumazet wrote:
> On Wed, Dec 4, 2024 at 12:41 PM Vladimir Oltean <vladimir.oltean@nxp.com> wrote:
> >
> > I meant: linkwatch runs periodically, via linkwatch_event(). Isn't there
> > a chance that linkwatch_event() can run once, immediately after
> > __rtnl_unlock() in netdev_run_todo(), while the netdev is in the
> > NETREG_UNREGISTERING state? Won't that create problems for __dev_get_by_index()
> > too? I guess it depends on when the netns is torn down, which I couldn't find.
> 
> I think lweventlist_lock and dev->link_watch_list are supposed to
> synchronize things.
> 
> linkwatch_sync_dev() only calls linkwatch_do_dev() if the device was
> atomically unlinked from lweventlist

No, I don't mean calls from linkwatch_sync_dev(). I mean other call
paths towards linkwatch_do_dev(), like for example linkwatch_fire_event() -
carrier down, whatever. Can't these be pending on an unregistering
net_device at the time we run __rtnl_unlock() in netdev_run_todo?
Otherwise, why would netdev_wait_allrefs_any() have a linkwatch_run_queue()
call just later?

Re: [PATCH net] net: avoid potential UAF in default_operstate()

[Eric Dumazet]

On Wed, Dec 4, 2024 at 1:57 PM Vladimir Oltean <vladimir.oltean@nxp.com> wrote:
>
> On Wed, Dec 04, 2024 at 12:46:11PM +0100, Eric Dumazet wrote:
> > On Wed, Dec 4, 2024 at 12:41 PM Vladimir Oltean <vladimir.oltean@nxp.com> wrote:
> > >
> > > I meant: linkwatch runs periodically, via linkwatch_event(). Isn't there
> > > a chance that linkwatch_event() can run once, immediately after
> > > __rtnl_unlock() in netdev_run_todo(), while the netdev is in the
> > > NETREG_UNREGISTERING state? Won't that create problems for __dev_get_by_index()
> > > too? I guess it depends on when the netns is torn down, which I couldn't find.
> >
> > I think lweventlist_lock and dev->link_watch_list are supposed to
> > synchronize things.
> >
> > linkwatch_sync_dev() only calls linkwatch_do_dev() if the device was
> > atomically unlinked from lweventlist
>
> No, I don't mean calls from linkwatch_sync_dev(). I mean other call
> paths towards linkwatch_do_dev(), like for example linkwatch_fire_event() -
> carrier down, whatever. Can't these be pending on an unregistering
> net_device at the time we run __rtnl_unlock() in netdev_run_todo?
> Otherwise, why would netdev_wait_allrefs_any() have a linkwatch_run_queue()
> call just later?

I do not know, this predates git history.

All these questions seem orthogonal.
My patch fixes an issue added recently. not something added 10 years ago.
I suggest we fix proven issues first, step by step.
If you want to take over and send a series, just say so.

Thank you.

Re: [PATCH net] net: avoid potential UAF in default_operstate()

[Vladimir Oltean]

On Wed, Dec 04, 2024 at 02:38:14PM +0100, Eric Dumazet wrote:
> On Wed, Dec 4, 2024 at 1:57 PM Vladimir Oltean <vladimir.oltean@nxp.com> wrote:
> >
> > On Wed, Dec 04, 2024 at 12:46:11PM +0100, Eric Dumazet wrote:
> > > On Wed, Dec 4, 2024 at 12:41 PM Vladimir Oltean <vladimir.oltean@nxp.com> wrote:
> > > >
> > > > I meant: linkwatch runs periodically, via linkwatch_event(). Isn't there
> > > > a chance that linkwatch_event() can run once, immediately after
> > > > __rtnl_unlock() in netdev_run_todo(), while the netdev is in the
> > > > NETREG_UNREGISTERING state? Won't that create problems for __dev_get_by_index()
> > > > too? I guess it depends on when the netns is torn down, which I couldn't find.
> > >
> > > I think lweventlist_lock and dev->link_watch_list are supposed to
> > > synchronize things.
> > >
> > > linkwatch_sync_dev() only calls linkwatch_do_dev() if the device was
> > > atomically unlinked from lweventlist
> >
> > No, I don't mean calls from linkwatch_sync_dev(). I mean other call
> > paths towards linkwatch_do_dev(), like for example linkwatch_fire_event() -
> > carrier down, whatever. Can't these be pending on an unregistering
> > net_device at the time we run __rtnl_unlock() in netdev_run_todo?
> > Otherwise, why would netdev_wait_allrefs_any() have a linkwatch_run_queue()
> > call just later?
> 
> I do not know, this predates git history.
> 
> All these questions seem orthogonal.
> My patch fixes an issue added recently. not something added 10 years ago.
> I suggest we fix proven issues first, step by step.
> If you want to take over and send a series, just say so.
> 
> Thank you.

My understanding is certainly fuzzy, but I am not talking about some
behavior from 10 years ago. If I made default_operstate() require
rtnl_mutex last year, I did so for all call paths, not just for the
direct linkwatch_sync_dev() call that you point out. I agree we can take
them step by step if the UNREGISTERING state also proves problematic
(I don't have enough data now), but I disagree that the problem is
orthogonal.

Re: [PATCH net] net: avoid potential UAF in default_operstate()

[Vladimir Oltean]

On Tue, Dec 03, 2024 at 05:09:33PM +0000, Eric Dumazet wrote:
> syzbot reported an UAF in default_operstate() [1]
> 
> Issue is a race between device and netns dismantles.
> 
> After calling __rtnl_unlock() from netdev_run_todo(),
> we can not assume the netns of each device is still alive.
> 
> Make sure the device is not in NETREG_UNREGISTERED state,
> and add an ASSERT_RTNL() before the call to
> __dev_get_by_index().
> 
> We might move this ASSERT_RTNL() in __dev_get_by_index()
> in the future.
> 
> Fixes: 8c55facecd7a ("net: linkwatch: only report IF_OPER_LOWERLAYERDOWN if iflink is actually down")
> Reported-by: syzbot+1939f24bdb783e9e43d9@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/netdev/674f3a18.050a0220.48a03.0041.GAE@google.com/T/#u
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---
> Cc: Vladimir Oltean <vladimir.oltean@nxp.com>
> ---

For now:

Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>

Re: [PATCH net] net: avoid potential UAF in default_operstate()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Paolo Abeni <pabeni@redhat.com>:

On Tue,  3 Dec 2024 17:09:33 +0000 you wrote:
> syzbot reported an UAF in default_operstate() [1]
> 
> Issue is a race between device and netns dismantles.
> 
> After calling __rtnl_unlock() from netdev_run_todo(),
> we can not assume the netns of each device is still alive.
> 
> [...]

Here is the summary with links:
  - [net] net: avoid potential UAF in default_operstate()
    https://git.kernel.org/netdev/net/c/750e51603395

You are awesome, thank you!
-- 
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