Subject: [syzbot] [kernel?] KASAN: slab-use-after-free Read in __unix_gc

From: syzbot <[email-masked]>
Date: Fri, 09 Feb 2024 06:57:17 -0800

Hello,

syzbot found the following issue on:

HEAD commit:    e7689879d14e ethtool: do not use rtnl in ethnl_default_dum..
git tree:       net-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1195b6e0180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ac1116e4986e7570
dashboard link: https://syzkaller.appspot.com/bug?extid=5a630f8ca0120ab43f55
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=121d9b5c180000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=165f9cec180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c5b791d72e1e/disk-e7689879.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/472cf2131e7b/vmlinux-e7689879.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c1e5a4b33244/bzImage-e7689879.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

==================================================================
BUG: KASAN: slab-use-after-free in __unix_gc+0xe0f/0xf70
Read of size 8 at addr ffff8880237e3640 by task kworker/u4:4/59

CPU: 0 PID: 59 Comm: kworker/u4:4 Not tainted 6.8.0-rc3-syzkaller-00766-ge7689879d14e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
Workqueue: events_unbound __unix_gc
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2e0 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x167/0x540 mm/kasan/report.c:488
 kasan_report+0x142/0x180 mm/kasan/report.c:601
 __unix_gc+0xe0f/0xf70
 process_one_work kernel/workqueue.c:2633 [inline]
 process_scheduled_works+0x913/0x1420 kernel/workqueue.c:2706
 worker_thread+0xa5f/0x1000 kernel/workqueue.c:2787
 kthread+0x2ef/0x390 kernel/kthread.c:388
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:242
 </TASK>

Allocated by task 5076:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
 unpoison_slab_object mm/kasan/common.c:314 [inline]
 __kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:340
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook mm/slub.c:3813 [inline]
 slab_alloc_node mm/slub.c:3860 [inline]
 kmem_cache_alloc+0x16f/0x340 mm/slub.c:3867
 sk_prot_alloc+0x58/0x210 net/core/sock.c:2073
 sk_alloc+0x38/0x370 net/core/sock.c:2132
 unix_create1+0xb4/0x7f0
 unix_create+0x14e/0x200 net/unix/af_unix.c:1047
 __sock_create+0x48f/0x920 net/socket.c:1571
 sock_create net/socket.c:1622 [inline]
 __sys_socketpair+0x33d/0x720 net/socket.c:1773
 __do_sys_socketpair net/socket.c:1822 [inline]
 __se_sys_socketpair net/socket.c:1819 [inline]
 __x64_sys_socketpair+0x9b/0xb0 net/socket.c:1819
 do_syscall_64+0xf9/0x240
 entry_SYSCALL_64_after_hwframe+0x6f/0x77

Freed by task 23:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
 kasan_save_free_info+0x4e/0x60 mm/kasan/generic.c:640
 poison_slab_object+0xa6/0xe0 mm/kasan/common.c:241
 __kasan_slab_free+0x34/0x70 mm/kasan/common.c:257
 kasan_slab_free include/linux/kasan.h:184 [inline]
 slab_free_hook mm/slub.c:2121 [inline]
 slab_free mm/slub.c:4299 [inline]
 kmem_cache_free+0x102/0x2a0 mm/slub.c:4363
 sk_prot_free net/core/sock.c:2113 [inline]
 __sk_destruct+0x470/0x5f0 net/core/sock.c:2207
 sock_put include/net/sock.h:1961 [inline]
 unix_release_sock+0x903/0xd20 net/unix/af_unix.c:649
 unix_release+0x91/0xc0 net/unix/af_unix.c:1062
 __sock_release net/socket.c:659 [inline]
 sock_close+0xbc/0x240 net/socket.c:1421
 __fput+0x429/0x8a0 fs/file_table.c:376
 delayed_fput+0x59/0x80 fs/file_table.c:399
 process_one_work kernel/workqueue.c:2633 [inline]
 process_scheduled_works+0x913/0x1420 kernel/workqueue.c:2706
 worker_thread+0xa5f/0x1000 kernel/workqueue.c:2787
 kthread+0x2ef/0x390 kernel/kthread.c:388
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:242

The buggy address belongs to the object at ffff8880237e3000
 which belongs to the cache UNIX-STREAM of size 1920
The buggy address is located 1600 bytes inside of
 freed 1920-byte region [ffff8880237e3000, ffff8880237e3780)

The buggy address belongs to the physical page:
page:ffffea00008df800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x237e0
head:ffffea00008df800 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff8880183aa280 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080100010 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 5069, tgid 5069 (sftp-server), ts 69550911589, free_ts 69532294849
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1ea/0x210 mm/page_alloc.c:1533
 prep_new_page mm/page_alloc.c:1540 [inline]
 get_page_from_freelist+0x33ea/0x3580 mm/page_alloc.c:3311
 __alloc_pages+0x255/0x680 mm/page_alloc.c:4567
 __alloc_pages_node include/linux/gfp.h:238 [inline]
 alloc_pages_node include/linux/gfp.h:261 [inline]
 alloc_slab_page+0x5f/0x160 mm/slub.c:2190
 allocate_slab mm/slub.c:2354 [inline]
 new_slab+0x84/0x2f0 mm/slub.c:2407
 ___slab_alloc+0xd17/0x13e0 mm/slub.c:3540
 __slab_alloc mm/slub.c:3625 [inline]
 __slab_alloc_node mm/slub.c:3678 [inline]
 slab_alloc_node mm/slub.c:3850 [inline]
 kmem_cache_alloc+0x24d/0x340 mm/slub.c:3867
 sk_prot_alloc+0x58/0x210 net/core/sock.c:2073
 sk_alloc+0x38/0x370 net/core/sock.c:2132
 unix_create1+0xb4/0x7f0
 unix_stream_connect+0x348/0x1110 net/unix/af_unix.c:1511
 __sys_connect_file net/socket.c:2048 [inline]
 __sys_connect+0x2df/0x310 net/socket.c:2065
 __do_sys_connect net/socket.c:2075 [inline]
 __se_sys_connect net/socket.c:2072 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:2072
 do_syscall_64+0xf9/0x240
 entry_SYSCALL_64_after_hwframe+0x6f/0x77
page last free pid 5069 tgid 5069 stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1140 [inline]
 free_unref_page_prepare+0x968/0xa90 mm/page_alloc.c:2346
 free_unref_page+0x37/0x3f0 mm/page_alloc.c:2486
 discard_slab mm/slub.c:2453 [inline]
 __put_partials+0xeb/0x130 mm/slub.c:2922
 put_cpu_partial+0x17b/0x250 mm/slub.c:2997
 __slab_free+0x302/0x410 mm/slub.c:4166
 qlink_free mm/kasan/quarantine.c:160 [inline]
 qlist_free_all+0x6d/0xd0 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x14f/0x170 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x23/0x80 mm/kasan/common.c:324
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook mm/slub.c:3813 [inline]
 slab_alloc_node mm/slub.c:3860 [inline]
 kmem_cache_alloc+0x16f/0x340 mm/slub.c:3867
 vm_area_alloc+0x24/0x1d0 kernel/fork.c:465
 mmap_region+0xbd8/0x1fa0 mm/mmap.c:2806
 do_mmap+0x7ae/0xe60 mm/mmap.c:1379
 vm_mmap_pgoff+0x1e2/0x420 mm/util.c:556
 ksys_mmap_pgoff+0x503/0x6e0 mm/mmap.c:1425
 do_syscall_64+0xf9/0x240
 entry_SYSCALL_64_after_hwframe+0x6f/0x77

Memory state around the buggy address:
 ffff8880237e3500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880237e3580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880237e3600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff8880237e3680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880237e3700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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