KASAN: use-after-free Read in unix_stream_read_actor

Status: fixed on 2023/12/18 16:47
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+a4f9427caf72d1b98445@syzkaller.appspotmail.com
Fix commit: 4b7b492615cf af_unix: fix use-after-free in unix_stream_read_actor()
First crash: 993d, last: 989d
Fix bisection: fixed by (bisect log) :
commit d179189eec426fe4801e4b91efa1889faed12700
Author: Eric Dumazet <edumazet@google.com>
Date: Mon Nov 13 13:49:38 2023 +0000

  af_unix: fix use-after-free in unix_stream_read_actor()

  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2023/11/11 linux-6.1.y (ToT) fb2635ac69ab C [report] KASAN: use-after-free Read in __skb_datagram_iter
2023/11/11 upstream (ToT) 3ca112b71f35 C Didn't crash
▶ ▼ Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-6-1 KASAN: use-after-free Read in unix_stream_read_actor missing-backport origin:upstream 19 syz, C done done 2 919d 993d 0/2 auto-obsoleted due to no activity on 2024/05/03 09:45
linux-5.15 KASAN: use-after-free Read in unix_stream_read_actor origin:lts-only 19 syz, C done 1 991d 993d 3/3 fixed on 2023/12/13 18:20
android-5-15 KASAN: use-after-free Read in unix_stream_read_actor origin:upstream 19 syz, C 1 993d 993d 0/2 auto-obsoleted due to no activity on 2024/02/19 03:43
upstream KASAN: slab-use-after-free Read in unix_stream_read_actor (2) net 19 syz, C inconclusive 4 699d 694d 28/29 fixed on 2024/10/22 11:56
upstream KASAN: slab-use-after-free Read in unix_stream_read_actor net 19 syz, C error 6 977d 993d 25/29 fixed on 2024/01/20 21:18
android-6-12 KASAN: slab-use-after-free Read in unix_stream_read_actor origin:lts 19 syz, C 2 382d 383d 0/1 auto-obsoleted due to no activity on 2025/10/11 14:25
▶ ▼ Fix bisection attempts (2)
Created Duration User Patch Repo Result
2023/12/15 07:47 3h51m bisect fix linux-6.1.y OK (1) job log
2023/11/15 04:46 2h19m fix candidate upstream OK (0) job log log

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in unix_stream_read_actor+0x9e/0xa0 net/unix/af_unix.c:2920
Read of size 4 at addr ffff888078cd9184 by task syz-executor293/4250

CPU: 0 PID: 4250 Comm: syz-executor293 Not tainted 6.1.62-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:284 [inline]
 print_report+0x15f/0x4f0 mm/kasan/report.c:395
 kasan_report+0x136/0x160 mm/kasan/report.c:495
 unix_stream_read_actor+0x9e/0xa0 net/unix/af_unix.c:2920
 unix_stream_recv_urg+0x1bb/0x300 net/unix/af_unix.c:2647
 unix_stream_read_generic+0x2104/0x21e0 net/unix/af_unix.c:2726
 unix_stream_recvmsg+0x222/0x2b0 net/unix/af_unix.c:2957
 ____sys_recvmsg+0x285/0x530
 ___sys_recvmsg net/socket.c:2760 [inline]
 __sys_recvmsg+0x2e9/0x3d0 net/socket.c:2790
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f4e215024e9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 18 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f4e21481228 EFLAGS: 00000246 ORIG_RAX: 000000000000002f
RAX: ffffffffffffffda RBX: 0000000000000024 RCX: 00007f4e215024e9
RDX: 0000000040010083 RSI: 0000000020000140 RDI: 0000000000000004
RBP: 00007f4e2158c348 R08: 00007f4e214816c0 R09: 00007f4e214816c0
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f4e2158c340
R13: 00007f4e2158c34c R14: 00007fff157e2d70 R15: 00007fff157e2e58
 </TASK>

Allocated by task 4249:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 __kasan_slab_alloc+0x65/0x70 mm/kasan/common.c:328
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x52/0x3a0 mm/slab.h:737
 slab_alloc_node mm/slub.c:3398 [inline]
 kmem_cache_alloc_node+0x136/0x310 mm/slub.c:3443
 __alloc_skb+0xde/0x670 net/core/skbuff.c:505
 alloc_skb include/linux/skbuff.h:1276 [inline]
 alloc_skb_with_frags+0xa4/0x740 net/core/skbuff.c:6153
 sock_alloc_send_pskb+0x915/0xa50 net/core/sock.c:2738
 sock_alloc_send_skb include/net/sock.h:1907 [inline]
 queue_oob+0x102/0x8e0 net/unix/af_unix.c:2114
 unix_stream_sendmsg+0xe10/0x1070 net/unix/af_unix.c:2251
 sock_sendmsg_nosec net/socket.c:716 [inline]
 __sock_sendmsg net/socket.c:728 [inline]
 ____sys_sendmsg+0x59e/0x8f0 net/socket.c:2499
 ___sys_sendmsg net/socket.c:2553 [inline]
 __sys_sendmsg+0x2a9/0x390 net/socket.c:2582
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 4249:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x27/0x40 mm/kasan/generic.c:516
 ____kasan_slab_free+0xd6/0x120 mm/kasan/common.c:236
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1724 [inline]
 slab_free_freelist_hook mm/slub.c:1750 [inline]
 slab_free mm/slub.c:3661 [inline]
 kmem_cache_free+0x292/0x510 mm/slub.c:3683
 queue_oob+0x52c/0x8e0 net/unix/af_unix.c:2145
 unix_stream_sendmsg+0xe10/0x1070 net/unix/af_unix.c:2251
 sock_sendmsg_nosec net/socket.c:716 [inline]
 __sock_sendmsg net/socket.c:728 [inline]
 ____sys_sendmsg+0x59e/0x8f0 net/socket.c:2499
 ___sys_sendmsg net/socket.c:2553 [inline]
 __sys_sendmsg+0x2a9/0x390 net/socket.c:2582
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff888078cd9140
 which belongs to the cache skbuff_head_cache of size 240
The buggy address is located 68 bytes inside of
 240-byte region [ffff888078cd9140, ffff888078cd9230)

The buggy address belongs to the physical page:
page:ffffea0001e33640 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x78cd9
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 0000000000000000 dead000000000122 ffff888141e54500
raw: 0000000000000000 00000000000c000c 00000001ffffffff 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 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 4249, tgid 4247 (syz-executor293), ts 70820582570, free_ts 70763899994
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x18d/0x1b0 mm/page_alloc.c:2513
 prep_new_page mm/page_alloc.c:2520 [inline]
 get_page_from_freelist+0x31a1/0x3320 mm/page_alloc.c:4279
 __alloc_pages+0x28d/0x770 mm/page_alloc.c:5545
 alloc_slab_page+0x6a/0x150 mm/slub.c:1794
 allocate_slab mm/slub.c:1939 [inline]
 new_slab+0x84/0x2d0 mm/slub.c:1992
 ___slab_alloc+0xc20/0x1270 mm/slub.c:3180
 __slab_alloc mm/slub.c:3279 [inline]
 slab_alloc_node mm/slub.c:3364 [inline]
 kmem_cache_alloc_node+0x1cf/0x310 mm/slub.c:3443
 __alloc_skb+0xde/0x670 net/core/skbuff.c:505
 alloc_skb include/linux/skbuff.h:1276 [inline]
 alloc_skb_with_frags+0xa4/0x740 net/core/skbuff.c:6153
 sock_alloc_send_pskb+0x915/0xa50 net/core/sock.c:2738
 sock_alloc_send_skb include/net/sock.h:1907 [inline]
 queue_oob+0x102/0x8e0 net/unix/af_unix.c:2114
 unix_stream_sendmsg+0xe10/0x1070 net/unix/af_unix.c:2251
 sock_sendmsg_nosec net/socket.c:716 [inline]
 __sock_sendmsg net/socket.c:728 [inline]
 ____sys_sendmsg+0x59e/0x8f0 net/socket.c:2499
 ___sys_sendmsg net/socket.c:2553 [inline]
 __sys_sendmsg+0x2a9/0x390 net/socket.c:2582
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/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:1440 [inline]
 free_pcp_prepare mm/page_alloc.c:1490 [inline]
 free_unref_page_prepare+0xf63/0x1120 mm/page_alloc.c:3358
 free_unref_page_list+0x663/0x900 mm/page_alloc.c:3499
 release_pages+0x2836/0x2b40 mm/swap.c:1055
 tlb_batch_pages_flush mm/mmu_gather.c:59 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:254 [inline]
 tlb_flush_mmu+0xfc/0x210 mm/mmu_gather.c:261
 tlb_finish_mmu+0xce/0x1f0 mm/mmu_gather.c:361
 exit_mmap+0x3c3/0x9f0 mm/mmap.c:3239
 __mmput+0x115/0x3c0 kernel/fork.c:1199
 exit_mm+0x226/0x300 kernel/exit.c:563
 do_exit+0x9f6/0x26a0 kernel/exit.c:856
 do_group_exit+0x202/0x2b0 kernel/exit.c:1019
 get_signal+0x16f7/0x17d0 kernel/signal.c:2862
 arch_do_signal_or_restart+0xb0/0x1a10 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x6a/0x100 kernel/entry/common.c:168
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:204
 __syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
 syscall_exit_to_user_mode+0x60/0x270 kernel/entry/common.c:297
 do_syscall_64+0x49/0xb0 arch/x86/entry/common.c:86

Memory state around the buggy address:
 ffff888078cd9080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
 ffff888078cd9100: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
>ffff888078cd9180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888078cd9200: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
 ffff888078cd9280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2023/11/11 07:38 linux-6.1.y fb2635ac69ab d80eec66 .config console log report syz C ci2-linux-6-1-kasan-perf KASAN: use-after-free Read in unix_stream_read_actor
* Struck through repros no longer work on HEAD.