[syzbot] KASAN: use-after-free Read in rxrpc_lookup_local

[syzbot] KASAN: use-after-free Read in rxrpc_lookup_local

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    c9f8d73645b6 net: mtk_eth_soc: enable flow offload support..
git tree:       net-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=12f9af53880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c608c21151db14f2
dashboard link: https://syzkaller.appspot.com/bug?extid=3538a6a72efa8b059c38
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17fedb97880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1749f597880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bf270f71d81b/disk-c9f8d736.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9df5873e74c3/vmlinux-c9f8d736.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4db90f01e6d3/bzImage-c9f8d736.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3538a6a72efa8b059c38@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in rxrpc_local_cmp_key net/rxrpc/local_object.c:53 [inline]
BUG: KASAN: use-after-free in rxrpc_lookup_local+0xdcf/0xfb0 net/rxrpc/local_object.c:224
Read of size 2 at addr ffff888022b3521c by task syz-executor112/3641

CPU: 0 PID: 3641 Comm: syz-executor112 Not tainted 6.1.0-rc7-syzkaller-01810-gc9f8d73645b6 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:284 [inline]
 print_report+0x15e/0x45d mm/kasan/report.c:395
 kasan_report+0xbf/0x1f0 mm/kasan/report.c:495
 rxrpc_local_cmp_key net/rxrpc/local_object.c:53 [inline]
 rxrpc_lookup_local+0xdcf/0xfb0 net/rxrpc/local_object.c:224
 rxrpc_bind+0x35e/0x5c0 net/rxrpc/af_rxrpc.c:150
 __sys_bind+0x1ed/0x260 net/socket.c:1776
 __do_sys_bind net/socket.c:1787 [inline]
 __se_sys_bind net/socket.c:1785 [inline]
 __x64_sys_bind+0x73/0xb0 net/socket.c:1785
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f9f1c5edd39
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 14 00 00 90 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 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffdd21e4598 EFLAGS: 00000246 ORIG_RAX: 0000000000000031
RAX: ffffffffffffffda RBX: 000000000000dd76 RCX: 00007f9f1c5edd39
RDX: 0000000000000024 RSI: 0000000020000040 RDI: 0000000000000003
RBP: 0000000000000000 R08: 00007ffdd21e4738 R09: 00007ffdd21e4738
R10: 00007ffdd21e4010 R11: 0000000000000246 R12: 00007ffdd21e45ac
R13: 431bde82d7b634db R14: 0000000000000000 R15: 0000000000000000
 </TASK>

Allocated by task 3634:
 kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
 kasan_set_track+0x25/0x30 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:371 [inline]
 ____kasan_kmalloc mm/kasan/common.c:330 [inline]
 __kasan_kmalloc+0xa5/0xb0 mm/kasan/common.c:380
 kmalloc include/linux/slab.h:553 [inline]
 kzalloc include/linux/slab.h:689 [inline]
 rxrpc_alloc_local net/rxrpc/local_object.c:93 [inline]
 rxrpc_lookup_local+0x4d9/0xfb0 net/rxrpc/local_object.c:249
 rxrpc_bind+0x35e/0x5c0 net/rxrpc/af_rxrpc.c:150
 __sys_bind+0x1ed/0x260 net/socket.c:1776
 __do_sys_bind net/socket.c:1787 [inline]
 __se_sys_bind net/socket.c:1785 [inline]
 __x64_sys_bind+0x73/0xb0 net/socket.c:1785
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 3624:
 kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
 kasan_set_track+0x25/0x30 mm/kasan/common.c:52
 kasan_save_free_info+0x2e/0x40 mm/kasan/generic.c:511
 ____kasan_slab_free mm/kasan/common.c:236 [inline]
 ____kasan_slab_free+0x160/0x1c0 mm/kasan/common.c:200
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1724 [inline]
 slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1750
 slab_free mm/slub.c:3661 [inline]
 __kmem_cache_free+0xaf/0x3b0 mm/slub.c:3674
 rcu_do_batch kernel/rcu/tree.c:2250 [inline]
 rcu_core+0x81f/0x1980 kernel/rcu/tree.c:2510
 __do_softirq+0x1fb/0xadc kernel/softirq.c:571

Last potentially related work creation:
 kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
 __kasan_record_aux_stack+0xbc/0xd0 mm/kasan/generic.c:481
 call_rcu+0x9d/0x820 kernel/rcu/tree.c:2798
 rxrpc_put_local.part.0+0x128/0x170 net/rxrpc/local_object.c:332
 rxrpc_put_local+0x25/0x30 net/rxrpc/local_object.c:324
 rxrpc_release_sock net/rxrpc/af_rxrpc.c:888 [inline]
 rxrpc_release+0x237/0x550 net/rxrpc/af_rxrpc.c:914
 __sock_release+0xcd/0x280 net/socket.c:650
 sock_close+0x1c/0x20 net/socket.c:1365
 __fput+0x27c/0xa90 fs/file_table.c:320
 task_work_run+0x16f/0x270 kernel/task_work.c:179
 exit_task_work include/linux/task_work.h:38 [inline]
 do_exit+0xb3d/0x2a30 kernel/exit.c:820
 do_group_exit+0xd4/0x2a0 kernel/exit.c:950
 __do_sys_exit_group kernel/exit.c:961 [inline]
 __se_sys_exit_group kernel/exit.c:959 [inline]
 __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:959
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff888022b35000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 540 bytes inside of
 1024-byte region [ffff888022b35000, ffff888022b35400)

The buggy address belongs to the physical page:
page:ffffea00008acc00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x22b30
head:ffffea00008acc00 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 dead000000000122 ffff888012041dc0
raw: 0000000000000000 0000000000100010 00000001ffffffff 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 3624, tgid 3624 (sshd), ts 56650444929, free_ts 56632976403
 prep_new_page mm/page_alloc.c:2539 [inline]
 get_page_from_freelist+0x10b5/0x2d50 mm/page_alloc.c:4291
 __alloc_pages+0x1cb/0x5b0 mm/page_alloc.c:5558
 alloc_pages+0x1aa/0x270 mm/mempolicy.c:2285
 alloc_slab_page mm/slub.c:1794 [inline]
 allocate_slab+0x213/0x300 mm/slub.c:1939
 new_slab mm/slub.c:1992 [inline]
 ___slab_alloc+0xa91/0x1400 mm/slub.c:3180
 __slab_alloc.constprop.0+0x56/0xa0 mm/slub.c:3279
 slab_alloc_node mm/slub.c:3364 [inline]
 __kmem_cache_alloc_node+0x199/0x3e0 mm/slub.c:3437
 __do_kmalloc_node mm/slab_common.c:954 [inline]
 __kmalloc_node_track_caller+0x4b/0xc0 mm/slab_common.c:975
 kmalloc_reserve net/core/skbuff.c:438 [inline]
 __alloc_skb+0xe9/0x310 net/core/skbuff.c:511
 alloc_skb_fclone include/linux/skbuff.h:1319 [inline]
 tcp_stream_alloc_skb+0x3c/0x580 net/ipv4/tcp.c:862
 tcp_sendmsg_locked+0xc4f/0x2960 net/ipv4/tcp.c:1325
 tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1483
 inet_sendmsg+0x9d/0xe0 net/ipv4/af_inet.c:827
 sock_sendmsg_nosec net/socket.c:714 [inline]
 sock_sendmsg+0xd3/0x120 net/socket.c:734
 sock_write_iter+0x295/0x3d0 net/socket.c:1108
 call_write_iter include/linux/fs.h:2199 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x9ed/0xdd0 fs/read_write.c:584
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1459 [inline]
 free_pcp_prepare+0x65c/0xd90 mm/page_alloc.c:1509
 free_unref_page_prepare mm/page_alloc.c:3387 [inline]
 free_unref_page+0x1d/0x4d0 mm/page_alloc.c:3483
 __unfreeze_partials+0x17c/0x1a0 mm/slub.c:2586
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0x6a/0x170 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x184/0x210 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x66/0x90 mm/kasan/common.c:302
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook mm/slab.h:737 [inline]
 slab_alloc_node mm/slub.c:3398 [inline]
 __kmem_cache_alloc_node+0x2e2/0x3e0 mm/slub.c:3437
 __do_kmalloc_node mm/slab_common.c:954 [inline]
 __kmalloc+0x4a/0xd0 mm/slab_common.c:968
 kmalloc include/linux/slab.h:558 [inline]
 tomoyo_add_entry security/tomoyo/common.c:2022 [inline]
 tomoyo_supervisor+0xb60/0xf10 security/tomoyo/common.c:2094
 tomoyo_audit_env_log security/tomoyo/environ.c:36 [inline]
 tomoyo_env_perm+0x183/0x200 security/tomoyo/environ.c:63
 tomoyo_environ security/tomoyo/domain.c:672 [inline]
 tomoyo_find_next_domain+0x13d2/0x1f80 security/tomoyo/domain.c:879
 tomoyo_bprm_check_security security/tomoyo/tomoyo.c:101 [inline]
 tomoyo_bprm_check_security+0x125/0x1b0 security/tomoyo/tomoyo.c:91
 security_bprm_check+0x49/0xb0 security/security.c:869
 search_binary_handler fs/exec.c:1715 [inline]
 exec_binprm fs/exec.c:1768 [inline]
 bprm_execve fs/exec.c:1837 [inline]
 bprm_execve+0x732/0x19f0 fs/exec.c:1799
 do_execveat_common+0x724/0x890 fs/exec.c:1942
 do_execve fs/exec.c:2016 [inline]
 __do_sys_execve fs/exec.c:2092 [inline]
 __se_sys_execve fs/exec.c:2087 [inline]
 __x64_sys_execve+0x93/0xc0 fs/exec.c:2087

Memory state around the buggy address:
 ffff888022b35100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888022b35180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888022b35200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff888022b35280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888022b35300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

Re: [syzbot] KASAN: use-after-free Read in rxrpc_lookup_local

[David Howells]

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git master

rxrpc: Fix NULL deref in rxrpc_unuse_local()

Fix rxrpc_unuse_local() to get the debug_id *after* checking to see if
local is NULL.

Fixes: a2cf3264f331 ("rxrpc: Fold __rxrpc_unuse_local() into rxrpc_unuse_local()")
Reported-by: syzbot+3538a6a72efa8b059c38@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
---
 net/rxrpc/local_object.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)


diff --git a/net/rxrpc/local_object.c b/net/rxrpc/local_object.c
index 44222923c0d1..24ee585d9aaf 100644
--- a/net/rxrpc/local_object.c
+++ b/net/rxrpc/local_object.c
@@ -357,10 +357,11 @@ struct rxrpc_local *rxrpc_use_local(struct rxrpc_local *local,
  */
 void rxrpc_unuse_local(struct rxrpc_local *local, enum rxrpc_local_trace why)
 {
-	unsigned int debug_id = local->debug_id;
+	unsigned int debug_id;
 	int r, u;
 
 	if (local) {
+		debug_id = local->debug_id;
 		r = refcount_read(&local->ref);
 		u = atomic_dec_return(&local->active_users);
 		trace_rxrpc_local(debug_id, why, r, u);

Re: [syzbot] KASAN: use-after-free Read in rxrpc_lookup_local

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: use-after-free Read in rxrpc_lookup_local

==================================================================
BUG: KASAN: use-after-free in rxrpc_local_cmp_key net/rxrpc/local_object.c:53 [inline]
BUG: KASAN: use-after-free in rxrpc_lookup_local+0xdcf/0xfb0 net/rxrpc/local_object.c:224
Read of size 2 at addr ffff88807652021c by task syz-executor.0/4166

CPU: 0 PID: 4166 Comm: syz-executor.0 Not tainted 6.1.0-rc7-syzkaller-01816-gb93884eea26f-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:284 [inline]
 print_report+0x15e/0x45d mm/kasan/report.c:395
 kasan_report+0xbf/0x1f0 mm/kasan/report.c:495
 rxrpc_local_cmp_key net/rxrpc/local_object.c:53 [inline]
 rxrpc_lookup_local+0xdcf/0xfb0 net/rxrpc/local_object.c:224
 rxrpc_bind+0x35e/0x5c0 net/rxrpc/af_rxrpc.c:150
 __sys_bind+0x1ed/0x260 net/socket.c:1776
 __do_sys_bind net/socket.c:1787 [inline]
 __se_sys_bind net/socket.c:1785 [inline]
 __x64_sys_bind+0x73/0xb0 net/socket.c:1785
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f7809a8c0d9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f780a709168 EFLAGS: 00000246 ORIG_RAX: 0000000000000031
RAX: ffffffffffffffda RBX: 00007f7809babf80 RCX: 00007f7809a8c0d9
RDX: 0000000000000024 RSI: 0000000020000040 RDI: 0000000000000003
RBP: 00007f7809ae7ae9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fff714ad7bf R14: 00007f780a709300 R15: 0000000000022000
 </TASK>

Allocated by task 4161:
 kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
 kasan_set_track+0x25/0x30 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:371 [inline]
 ____kasan_kmalloc mm/kasan/common.c:330 [inline]
 __kasan_kmalloc+0xa5/0xb0 mm/kasan/common.c:380
 kmalloc include/linux/slab.h:553 [inline]
 kzalloc include/linux/slab.h:689 [inline]
 rxrpc_alloc_local net/rxrpc/local_object.c:93 [inline]
 rxrpc_lookup_local+0x4d9/0xfb0 net/rxrpc/local_object.c:249
 rxrpc_bind+0x35e/0x5c0 net/rxrpc/af_rxrpc.c:150
 __sys_bind+0x1ed/0x260 net/socket.c:1776
 __do_sys_bind net/socket.c:1787 [inline]
 __se_sys_bind net/socket.c:1785 [inline]
 __x64_sys_bind+0x73/0xb0 net/socket.c:1785
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 21:
 kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
 kasan_set_track+0x25/0x30 mm/kasan/common.c:52
 kasan_save_free_info+0x2e/0x40 mm/kasan/generic.c:511
 ____kasan_slab_free mm/kasan/common.c:236 [inline]
 ____kasan_slab_free+0x160/0x1c0 mm/kasan/common.c:200
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1724 [inline]
 slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1750
 slab_free mm/slub.c:3661 [inline]
 __kmem_cache_free+0xaf/0x3b0 mm/slub.c:3674
 rcu_do_batch kernel/rcu/tree.c:2250 [inline]
 rcu_core+0x81f/0x1980 kernel/rcu/tree.c:2510
 __do_softirq+0x1fb/0xadc kernel/softirq.c:571

Last potentially related work creation:
 kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
 __kasan_record_aux_stack+0xbc/0xd0 mm/kasan/generic.c:481
 call_rcu+0x9d/0x820 kernel/rcu/tree.c:2798
 rxrpc_put_local.part.0+0x128/0x170 net/rxrpc/local_object.c:332
 rxrpc_put_local+0x25/0x30 net/rxrpc/local_object.c:324
 rxrpc_release_sock net/rxrpc/af_rxrpc.c:888 [inline]
 rxrpc_release+0x237/0x550 net/rxrpc/af_rxrpc.c:914
 __sock_release+0xcd/0x280 net/socket.c:650
 sock_close+0x1c/0x20 net/socket.c:1365
 __fput+0x27c/0xa90 fs/file_table.c:320
 task_work_run+0x16f/0x270 kernel/task_work.c:179
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
 exit_to_user_mode_prepare+0x23c/0x250 kernel/entry/common.c:203
 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
 syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:296
 do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff888076520000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 540 bytes inside of
 1024-byte region [ffff888076520000, ffff888076520400)

The buggy address belongs to the physical page:
page:ffffea0001d94800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x76520
head:ffffea0001d94800 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 dead000000000122 ffff888012041dc0
raw: 0000000000000000 0000000000100010 00000001ffffffff 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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 4161, tgid 4160 (syz-executor.0), ts 79477960432, free_ts 79222719756
 prep_new_page mm/page_alloc.c:2539 [inline]
 get_page_from_freelist+0x10b5/0x2d50 mm/page_alloc.c:4291
 __alloc_pages+0x1cb/0x5b0 mm/page_alloc.c:5558
 alloc_pages+0x1aa/0x270 mm/mempolicy.c:2285
 alloc_slab_page mm/slub.c:1794 [inline]
 allocate_slab+0x213/0x300 mm/slub.c:1939
 new_slab mm/slub.c:1992 [inline]
 ___slab_alloc+0xa91/0x1400 mm/slub.c:3180
 __slab_alloc.constprop.0+0x56/0xa0 mm/slub.c:3279
 slab_alloc_node mm/slub.c:3364 [inline]
 __kmem_cache_alloc_node+0x199/0x3e0 mm/slub.c:3437
 kmalloc_trace+0x26/0x60 mm/slab_common.c:1045
 kmalloc include/linux/slab.h:553 [inline]
 kzalloc include/linux/slab.h:689 [inline]
 rxrpc_alloc_local net/rxrpc/local_object.c:93 [inline]
 rxrpc_lookup_local+0x4d9/0xfb0 net/rxrpc/local_object.c:249
 rxrpc_bind+0x35e/0x5c0 net/rxrpc/af_rxrpc.c:150
 __sys_bind+0x1ed/0x260 net/socket.c:1776
 __do_sys_bind net/socket.c:1787 [inline]
 __se_sys_bind net/socket.c:1785 [inline]
 __x64_sys_bind+0x73/0xb0 net/socket.c:1785
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1459 [inline]
 free_pcp_prepare+0x65c/0xd90 mm/page_alloc.c:1509
 free_unref_page_prepare mm/page_alloc.c:3387 [inline]
 free_unref_page+0x1d/0x4d0 mm/page_alloc.c:3483
 __unfreeze_partials+0x17c/0x1a0 mm/slub.c:2586
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0x6a/0x170 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x184/0x210 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x66/0x90 mm/kasan/common.c:302
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook mm/slab.h:737 [inline]
 slab_alloc_node mm/slub.c:3398 [inline]
 __kmem_cache_alloc_node+0x2e2/0x3e0 mm/slub.c:3437
 kmalloc_trace+0x26/0x60 mm/slab_common.c:1045
 kmalloc include/linux/slab.h:553 [inline]
 netdevice_queue_work drivers/infiniband/core/roce_gid_mgmt.c:643 [inline]
 netdevice_event+0x368/0x8f0 drivers/infiniband/core/roce_gid_mgmt.c:802
 notifier_call_chain+0xb5/0x200 kernel/notifier.c:87
 call_netdevice_notifiers_info+0xb5/0x130 net/core/dev.c:1944
 call_netdevice_notifiers_extack net/core/dev.c:1982 [inline]
 call_netdevice_notifiers net/core/dev.c:1996 [inline]
 dev_set_mac_address+0x2d7/0x3e0 net/core/dev.c:8791
 dev_set_mac_address_user+0x31/0x50 net/core/dev.c:8805
 do_setlink+0x18c4/0x3bb0 net/core/rtnetlink.c:2775
 __rtnl_newlink+0xd69/0x1840 net/core/rtnetlink.c:3590
 rtnl_newlink+0x68/0xa0 net/core/rtnetlink.c:3637

Memory state around the buggy address:
 ffff888076520100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888076520180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888076520200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff888076520280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888076520300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Tested on:

commit:         b93884ee net/ncsi: Silence runtime memcpy() false posi..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=144320db880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c608c21151db14f2
dashboard link: https://syzkaller.appspot.com/bug?extid=3538a6a72efa8b059c38
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
patch:          https://syzkaller.appspot.com/x/patch.diff?x=145e216b880000

Re: [syzbot] KASAN: use-after-free Read in rxrpc_lookup_local

[David Howells]

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git master

diff --git a/kernel/kthread.c b/kernel/kthread.c
index f97fd01a2932..1335c89c6225 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -336,7 +336,6 @@ static int kthread(void *_create)
 	void *data = create->data;
 	struct completion *done;
 	struct kthread *self;
-	int ret;
 
 	self = to_kthread(current);
 
@@ -365,17 +364,20 @@ static int kthread(void *_create)
 	 * or the creator may spend more time in wait_task_inactive().
 	 */
 	preempt_disable();
+	if (test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
+		preempt_enable();
+		create->result = ERR_PTR(-EINTR);
+		complete(done);
+		do_exit(0);
+	}
 	complete(done);
 	schedule_preempt_disabled();
 	preempt_enable();
 
-	ret = -EINTR;
-	if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
-		cgroup_kthread_ready();
-		__kthread_parkme(self);
-		ret = threadfn(data);
-	}
-	kthread_exit(ret);
+	cgroup_kthread_ready();
+	__kthread_parkme(self);
+	/* Run the actual thread function. */
+	kthread_exit(threadfn(data));
 }
 
 /* called from kernel_clone() to get node information for about to be created task */
diff --git a/net/rxrpc/local_object.c b/net/rxrpc/local_object.c
index 44222923c0d1..24ee585d9aaf 100644
--- a/net/rxrpc/local_object.c
+++ b/net/rxrpc/local_object.c
@@ -357,10 +357,11 @@ struct rxrpc_local *rxrpc_use_local(struct rxrpc_local *local,
  */
 void rxrpc_unuse_local(struct rxrpc_local *local, enum rxrpc_local_trace why)
 {
-	unsigned int debug_id = local->debug_id;
+	unsigned int debug_id;
 	int r, u;
 
 	if (local) {
+		debug_id = local->debug_id;
 		r = refcount_read(&local->ref);
 		u = atomic_dec_return(&local->active_users);
 		trace_rxrpc_local(debug_id, why, r, u);

Re: [syzbot] KASAN: use-after-free Read in rxrpc_lookup_local

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+3538a6a72efa8b059c38@syzkaller.appspotmail.com

Tested on:

commit:         a2220b54 Merge branch 'cn10kb-mac-block-support'
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=1589fa4d880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c608c21151db14f2
dashboard link: https://syzkaller.appspot.com/bug?extid=3538a6a72efa8b059c38
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1473515b880000

Note: testing is done by a robot and is best-effort only.

Re: [syzbot] KASAN: use-after-free Read in rxrpc_lookup_local

[David Howells]

Hillf Danton <hdanton@sina.com> wrote:

> Where is KTHREAD_SHOULD_STOP coming from? Given

Fair point.

David

Re: [syzbot] KASAN: use-after-free Read in rxrpc_lookup_local

[David Howells]

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git master

diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index e7dccab7b741..37f3aec784cc 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -287,6 +287,7 @@ struct rxrpc_local {
 	struct hlist_node	link;
 	struct socket		*socket;	/* my UDP socket */
 	struct task_struct	*io_thread;
+	struct completion	io_thread_ready; /* Indication that the I/O thread started */
 	struct rxrpc_sock __rcu	*service;	/* Service(s) listening on this endpoint */
 	struct rw_semaphore	defrag_sem;	/* control re-enablement of IP DF bit */
 	struct sk_buff_head	rx_queue;	/* Received packets */
diff --git a/net/rxrpc/io_thread.c b/net/rxrpc/io_thread.c
index d83ae3193032..e460e4151c16 100644
--- a/net/rxrpc/io_thread.c
+++ b/net/rxrpc/io_thread.c
@@ -426,6 +426,8 @@ int rxrpc_io_thread(void *data)
 	struct rxrpc_call *call;
 	struct sk_buff *skb;
 
+	complete(&local->io_thread_ready);
+
 	skb_queue_head_init(&rx_queue);
 
 	set_user_nice(current, MIN_NICE);
diff --git a/net/rxrpc/local_object.c b/net/rxrpc/local_object.c
index 44222923c0d1..d8dfd5459f50 100644
--- a/net/rxrpc/local_object.c
+++ b/net/rxrpc/local_object.c
@@ -96,6 +96,7 @@ static struct rxrpc_local *rxrpc_alloc_local(struct rxrpc_net *rxnet,
 		atomic_set(&local->active_users, 1);
 		local->rxnet = rxnet;
 		INIT_HLIST_NODE(&local->link);
+		init_completion(&local->io_thread_ready);
 		init_rwsem(&local->defrag_sem);
 		skb_queue_head_init(&local->rx_queue);
 		INIT_LIST_HEAD(&local->call_attend_q);
@@ -189,6 +190,7 @@ static int rxrpc_open_socket(struct rxrpc_local *local, struct net *net)
 		goto error_sock;
 	}
 
+	wait_for_completion(&local->io_thread_ready);
 	local->io_thread = io_thread;
 	_leave(" = 0");
 	return 0;
@@ -357,10 +359,11 @@ struct rxrpc_local *rxrpc_use_local(struct rxrpc_local *local,
  */
 void rxrpc_unuse_local(struct rxrpc_local *local, enum rxrpc_local_trace why)
 {
-	unsigned int debug_id = local->debug_id;
+	unsigned int debug_id;
 	int r, u;
 
 	if (local) {
+		debug_id = local->debug_id;
 		r = refcount_read(&local->ref);
 		u = atomic_dec_return(&local->active_users);
 		trace_rxrpc_local(debug_id, why, r, u);

Re: [syzbot] KASAN: use-after-free Read in rxrpc_lookup_local

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+3538a6a72efa8b059c38@syzkaller.appspotmail.com

Tested on:

commit:         d8b879c0 Merge branch 'net-ethernet-ti-am65-cpsw-fix-s..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=14186857880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c608c21151db14f2
dashboard link: https://syzkaller.appspot.com/bug?extid=3538a6a72efa8b059c38
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1257cd23880000

Note: testing is done by a robot and is best-effort only.

Re: [syzbot] KASAN: use-after-free Read in rxrpc_lookup_local

[David Howells]

Hillf Danton <hdanton@sina.com> wrote:

> > Hmmm...  That can't be the whole explanation.  As you say, the hlist_del is
> > done under the mutex in rxrpc_destroy_local() - the same as the
> > hlist_add/hlist_replace and the search in rxrpc_lookup_local().
> 
> The uaf is simple and due to local ep freed without being deleted from
> rxnet->local_endpoints while the list walker in rxrpc_lookup_local() stumbles
> on it. rxrpc_destroy_local() is irrelevant as per the syzbot report.

No, that's not the explanation.  We can't get that far unless the I/O thread
got started - kthread_run() has to wait for the task_struct pointer to become
available - and the I/O thread should remove the link before it exits and
before the rxrpc_local object is deallocated.

I've tracked the problem down.  It's due to kthread(), specifically this bit:

	preempt_disable();
	complete(done);
	schedule_preempt_disabled();
	preempt_enable();

	ret = -EINTR;
	if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
		cgroup_kthread_ready();
		__kthread_parkme(self);
		ret = threadfn(data);
	}

So the complete() is done before we've decided if we're going to call
threadfn() or return an error.  This permits kthread_run() to resume before
we've checked KTHREAD_SHOULD_STOP - thus if kthread_stop() is called quickly
enough by the rxrpc socket being released, kthread() skips calling threadfn(),
but kthread_run() returns success.

The fact that the thread didn't start doesn't get seen until kthread_stop() is
called.

I think the above code needs rearranging slightly.  KTHREAD_SHOULD_STOP should
be tested and, if needed EINTR set, *before* complete(done).  That way
kthread_run() will return -EINTR in this case.

David

Re: [syzbot] KASAN: use-after-free Read in rxrpc_lookup_local

[David Howells]

Hillf Danton <hdanton@sina.com> wrote:

> To fix the uaf, destroy local in workqueue because of hlist_del under mutex.

Hmmm...  That can't be the whole explanation.  As you say, the hlist_del is
done under the mutex in rxrpc_destroy_local() - the same as the
hlist_add/hlist_replace and the search in rxrpc_lookup_local().

There should be no need to bump it off to a worker thread - the destruction is
in process context already - and doing the destruction not in the I/O thread
violates other assumptions, so I'm not convinced this patch is a valid fix.

I wonder if, under some circumstances, the I/O thread is managing to start and
destroy itself *before* rxrpc_lookup_local() adds itself to the
local_endpoints list.  Possibly I should offload the add to the I/O thread and
use a completion to wait for it to set up.

David

Re: [syzbot] KASAN: use-after-free Read in rxrpc_lookup_local

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+3538a6a72efa8b059c38@syzkaller.appspotmail.com

Tested on:

commit:         c9f8d736 net: mtk_eth_soc: enable flow offload support..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1205f597880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c608c21151db14f2
dashboard link: https://syzkaller.appspot.com/bug?extid=3538a6a72efa8b059c38
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
patch:          https://syzkaller.appspot.com/x/patch.diff?x=13c7a51d880000

Note: testing is done by a robot and is best-effort only.