From: Eric Dumazet edumazet@google.com

commit dba5bdd57bea587ea4f0b79b03c71135f84a7e8b upstream.

syzbot reported an UAF in ip_mc_sf_allow() [1]

Whenever RCU protected list replaces an object, the pointer to the new object needs to be updated _before_ the call to kfree_rcu() or call_rcu()

Because kfree_rcu(ptr, rcu) got support for NULL ptr only recently in commit 12edff045bc6 ("rcu: Make kfree_rcu() ignore NULL pointers"), I chose to use the conditional to make sure stable backports won't miss this detail.

if (psl) kfree_rcu(psl, rcu);

net/ipv6/mcast.c has similar issues, addressed in a separate patch.

[1] BUG: KASAN: use-after-free in ip_mc_sf_allow+0x6bb/0x6d0 net/ipv4/igmp.c:2655 Read of size 4 at addr ffff88807d37b904 by task syz-executor.5/908

CPU: 0 PID: 908 Comm: syz-executor.5 Not tainted 5.18.0-rc4-syzkaller-00064-g8f4dd16603ce #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description.constprop.0.cold+0xeb/0x467 mm/kasan/report.c:313 print_report mm/kasan/report.c:429 [inline] kasan_report.cold+0xf4/0x1c6 mm/kasan/report.c:491 ip_mc_sf_allow+0x6bb/0x6d0 net/ipv4/igmp.c:2655 raw_v4_input net/ipv4/raw.c:190 [inline] raw_local_deliver+0x4d1/0xbe0 net/ipv4/raw.c:218 ip_protocol_deliver_rcu+0xcf/0xb30 net/ipv4/ip_input.c:193 ip_local_deliver_finish+0x2ee/0x4c0 net/ipv4/ip_input.c:233 NF_HOOK include/linux/netfilter.h:307 [inline] NF_HOOK include/linux/netfilter.h:301 [inline] ip_local_deliver+0x1b3/0x200 net/ipv4/ip_input.c:254 dst_input include/net/dst.h:461 [inline] ip_rcv_finish+0x1cb/0x2f0 net/ipv4/ip_input.c:437 NF_HOOK include/linux/netfilter.h:307 [inline] NF_HOOK include/linux/netfilter.h:301 [inline] ip_rcv+0xaa/0xd0 net/ipv4/ip_input.c:556 __netif_receive_skb_one_core+0x114/0x180 net/core/dev.c:5405 __netif_receive_skb+0x24/0x1b0 net/core/dev.c:5519 netif_receive_skb_internal net/core/dev.c:5605 [inline] netif_receive_skb+0x13e/0x8e0 net/core/dev.c:5664 tun_rx_batched.isra.0+0x460/0x720 drivers/net/tun.c:1534 tun_get_user+0x28b7/0x3e30 drivers/net/tun.c:1985 tun_chr_write_iter+0xdb/0x200 drivers/net/tun.c:2015 call_write_iter include/linux/fs.h:2050 [inline] new_sync_write+0x38a/0x560 fs/read_write.c:504 vfs_write+0x7c0/0xac0 fs/read_write.c:591 ksys_write+0x127/0x250 fs/read_write.c:644 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f3f12c3bbff Code: 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 99 fd ff ff 48 8b 54 24 18 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 31 44 89 c7 48 89 44 24 08 e8 cc fd ff ff 48 RSP: 002b:00007f3f13ea9130 EFLAGS: 00000293 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f3f12d9bf60 RCX: 00007f3f12c3bbff RDX: 0000000000000036 RSI: 0000000020002ac0 RDI: 00000000000000c8 RBP: 00007f3f12ce308d R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000036 R11: 0000000000000293 R12: 0000000000000000 R13: 00007fffb68dd79f R14: 00007f3f13ea9300 R15: 0000000000022000 </TASK>

Allocated by task 908: kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38 kasan_set_track mm/kasan/common.c:45 [inline] set_alloc_info mm/kasan/common.c:436 [inline] ____kasan_kmalloc mm/kasan/common.c:515 [inline] ____kasan_kmalloc mm/kasan/common.c:474 [inline] __kasan_kmalloc+0xa6/0xd0 mm/kasan/common.c:524 kasan_kmalloc include/linux/kasan.h:234 [inline] __do_kmalloc mm/slab.c:3710 [inline] __kmalloc+0x209/0x4d0 mm/slab.c:3719 kmalloc include/linux/slab.h:586 [inline] sock_kmalloc net/core/sock.c:2501 [inline] sock_kmalloc+0xb5/0x100 net/core/sock.c:2492 ip_mc_source+0xba2/0x1100 net/ipv4/igmp.c:2392 do_ip_setsockopt net/ipv4/ip_sockglue.c:1296 [inline] ip_setsockopt+0x2312/0x3ab0 net/ipv4/ip_sockglue.c:1432 raw_setsockopt+0x274/0x2c0 net/ipv4/raw.c:861 __sys_setsockopt+0x2db/0x6a0 net/socket.c:2180 __do_sys_setsockopt net/socket.c:2191 [inline] __se_sys_setsockopt net/socket.c:2188 [inline] __x64_sys_setsockopt+0xba/0x150 net/socket.c:2188 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 753: kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38 kasan_set_track+0x21/0x30 mm/kasan/common.c:45 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370 ____kasan_slab_free mm/kasan/common.c:366 [inline] ____kasan_slab_free+0x13d/0x180 mm/kasan/common.c:328 kasan_slab_free include/linux/kasan.h:200 [inline] __cache_free mm/slab.c:3439 [inline] kmem_cache_free_bulk+0x69/0x460 mm/slab.c:3774 kfree_bulk include/linux/slab.h:437 [inline] kfree_rcu_work+0x51c/0xa10 kernel/rcu/tree.c:3318 process_one_work+0x996/0x1610 kernel/workqueue.c:2289 worker_thread+0x665/0x1080 kernel/workqueue.c:2436 kthread+0x2e9/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

Last potentially related work creation: kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38 __kasan_record_aux_stack+0x7e/0x90 mm/kasan/generic.c:348 kvfree_call_rcu+0x74/0x990 kernel/rcu/tree.c:3595 ip_mc_msfilter+0x712/0xb60 net/ipv4/igmp.c:2510 do_ip_setsockopt net/ipv4/ip_sockglue.c:1257 [inline] ip_setsockopt+0x32e1/0x3ab0 net/ipv4/ip_sockglue.c:1432 raw_setsockopt+0x274/0x2c0 net/ipv4/raw.c:861 __sys_setsockopt+0x2db/0x6a0 net/socket.c:2180 __do_sys_setsockopt net/socket.c:2191 [inline] __se_sys_setsockopt net/socket.c:2188 [inline] __x64_sys_setsockopt+0xba/0x150 net/socket.c:2188 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae

Second to last potentially related work creation: kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38 __kasan_record_aux_stack+0x7e/0x90 mm/kasan/generic.c:348 call_rcu+0x99/0x790 kernel/rcu/tree.c:3074 mpls_dev_notify+0x552/0x8a0 net/mpls/af_mpls.c:1656 notifier_call_chain+0xb5/0x200 kernel/notifier.c:84 call_netdevice_notifiers_info+0xb5/0x130 net/core/dev.c:1938 call_netdevice_notifiers_extack net/core/dev.c:1976 [inline] call_netdevice_notifiers net/core/dev.c:1990 [inline] unregister_netdevice_many+0x92e/0x1890 net/core/dev.c:10751 default_device_exit_batch+0x449/0x590 net/core/dev.c:11245 ops_exit_list+0x125/0x170 net/core/net_namespace.c:167 cleanup_net+0x4ea/0xb00 net/core/net_namespace.c:594 process_one_work+0x996/0x1610 kernel/workqueue.c:2289 worker_thread+0x665/0x1080 kernel/workqueue.c:2436 kthread+0x2e9/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

The buggy address belongs to the object at ffff88807d37b900 which belongs to the cache kmalloc-64 of size 64 The buggy address is located 4 bytes inside of 64-byte region [ffff88807d37b900, ffff88807d37b940)

The buggy address belongs to the physical page: page:ffffea0001f4dec0 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88807d37b180 pfn:0x7d37b flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000000200 ffff888010c41340 ffffea0001c795c8 ffff888010c40200 raw: ffff88807d37b180 ffff88807d37b000 000000010000001f 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 0, migratetype Unmovable, gfp_mask 0x342040(__GFP_IO|__GFP_NOWARN|__GFP_COMP|__GFP_HARDWALL|__GFP_THISNODE), pid 2963, tgid 2963 (udevd), ts 139732238007, free_ts 139730893262 prep_new_page mm/page_alloc.c:2441 [inline] get_page_from_freelist+0xba2/0x3e00 mm/page_alloc.c:4182 __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5408 __alloc_pages_node include/linux/gfp.h:587 [inline] kmem_getpages mm/slab.c:1378 [inline] cache_grow_begin+0x75/0x350 mm/slab.c:2584 cache_alloc_refill+0x27f/0x380 mm/slab.c:2957 ____cache_alloc mm/slab.c:3040 [inline] ____cache_alloc mm/slab.c:3023 [inline] __do_cache_alloc mm/slab.c:3267 [inline] slab_alloc mm/slab.c:3309 [inline] __do_kmalloc mm/slab.c:3708 [inline] __kmalloc+0x3b3/0x4d0 mm/slab.c:3719 kmalloc include/linux/slab.h:586 [inline] kzalloc include/linux/slab.h:714 [inline] tomoyo_encode2.part.0+0xe9/0x3a0 security/tomoyo/realpath.c:45 tomoyo_encode2 security/tomoyo/realpath.c:31 [inline] tomoyo_encode+0x28/0x50 security/tomoyo/realpath.c:80 tomoyo_realpath_from_path+0x186/0x620 security/tomoyo/realpath.c:288 tomoyo_get_realpath security/tomoyo/file.c:151 [inline] tomoyo_path_perm+0x21b/0x400 security/tomoyo/file.c:822 security_inode_getattr+0xcf/0x140 security/security.c:1350 vfs_getattr fs/stat.c:157 [inline] vfs_statx+0x16a/0x390 fs/stat.c:232 vfs_fstatat+0x8c/0xb0 fs/stat.c:255 __do_sys_newfstatat+0x91/0x110 fs/stat.c:425 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae page last free stack trace: reset_page_owner include/linux/page_owner.h:24 [inline] free_pages_prepare mm/page_alloc.c:1356 [inline] free_pcp_prepare+0x549/0xd20 mm/page_alloc.c:1406 free_unref_page_prepare mm/page_alloc.c:3328 [inline] free_unref_page+0x19/0x6a0 mm/page_alloc.c:3423 __vunmap+0x85d/0xd30 mm/vmalloc.c:2667 __vfree+0x3c/0xd0 mm/vmalloc.c:2715 vfree+0x5a/0x90 mm/vmalloc.c:2746 __do_replace+0x16b/0x890 net/ipv6/netfilter/ip6_tables.c:1117 do_replace net/ipv6/netfilter/ip6_tables.c:1157 [inline] do_ip6t_set_ctl+0x90d/0xb90 net/ipv6/netfilter/ip6_tables.c:1639 nf_setsockopt+0x83/0xe0 net/netfilter/nf_sockopt.c:101 ipv6_setsockopt+0x122/0x180 net/ipv6/ipv6_sockglue.c:1026 tcp_setsockopt+0x136/0x2520 net/ipv4/tcp.c:3696 __sys_setsockopt+0x2db/0x6a0 net/socket.c:2180 __do_sys_setsockopt net/socket.c:2191 [inline] __se_sys_setsockopt net/socket.c:2188 [inline] __x64_sys_setsockopt+0xba/0x150 net/socket.c:2188 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae

Memory state around the buggy address: ffff88807d37b800: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc ffff88807d37b880: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc

ffff88807d37b900: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc

^ ffff88807d37b980: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ffff88807d37ba00: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc

Fixes: c85bb41e9318 ("igmp: fix ip_mc_sf_allow race [v5]") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Cc: Flavio Leitner fbl@sysclose.org Signed-off-by: David S. Miller davem@davemloft.net --- This is the backport for 5.10. It might apply cleanly to older stable trees.

net/ipv4/igmp.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c index 0c321996c6eb0f20801a81a7ff9d2b134c0453bc..3817988a5a1d44e7b24c94568b75f72d94ad2104 100644 --- a/net/ipv4/igmp.c +++ b/net/ipv4/igmp.c @@ -2401,9 +2401,10 @@ int ip_mc_source(int add, int omode, struct sock *sk, struct newpsl->sl_addr[i] = psl->sl_addr[i]; /* decrease mem now to avoid the memleak warning */ atomic_sub(IP_SFLSIZE(psl->sl_max), &sk->sk_omem_alloc); - kfree_rcu(psl, rcu); } rcu_assign_pointer(pmc->sflist, newpsl); + if (psl) + kfree_rcu(psl, rcu); psl = newpsl; } rv = 1; /* > 0 for insert logic below if sl_count is 0 */ @@ -2501,11 +2502,13 @@ int ip_mc_msfilter(struct sock *sk, struct ip_msfilter *msf, int ifindex) psl->sl_count, psl->sl_addr, 0); /* decrease mem now to avoid the memleak warning */ atomic_sub(IP_SFLSIZE(psl->sl_max), &sk->sk_omem_alloc); - kfree_rcu(psl, rcu); - } else + } else { (void) ip_mc_del_src(in_dev, &msf->imsf_multiaddr, pmc->sfmode, 0, NULL, 0); + } rcu_assign_pointer(pmc->sflist, newpsl); + if (psl) + kfree_rcu(psl, rcu); pmc->sfmode = msf->imsf_fmode; err = 0; done: