Re: [syzbot] [perf?] KASAN: slab-use-after-free Read in __uprobe_unregister

[Oleg Nesterov <oleg@redhat.com>]

Hmm, bpf_uprobe_multi_link_attach() looks obviously wrong.

bpf_link_prime() is called after the

	for (i = 0; i < cnt; i++) {
		uprobe_register(...);
		...
	}

loop. If bpf_link_prime() fails, bpf_uprobe_multi_link_attach() just do
kvfree(uprobes) without _unregister(). In particular, this leaks the freed
bpf_uprobe->consumer in the uprobe->consumers list.

After that another _unregister() on the same uprobe can hit the problem.

I guess we need a simple patch for -stable...

Oleg.

On 08/10, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    6a0e38264012 Merge tag 'for-6.11-rc2-tag' of git://git.ker..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=13d4fc91980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=505ed4a1dd93463a
> dashboard link: https://syzkaller.appspot.com/bug?extid=f7a1c2c2711e4a780f19
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15fd9755980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1546c4e5980000
>
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-6a0e3826.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/dd9ba9302e4d/vmlinux-6a0e3826.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/aa3ef19fbf4e/bzImage-6a0e3826.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+f7a1c2c2711e4a780f19@syzkaller.appspotmail.com
>
> R10: 0000000000000001 R11: 0000000000000246 R12: 00007f4aa48c4618
> R13: 00007ffc0345d258 R14: 0000000000000001 R15: 0000000000000001
>  </TASK>
> ==================================================================
> BUG: KASAN: slab-use-after-free in consumer_del kernel/events/uprobes.c:772 [inline]
> BUG: KASAN: slab-use-after-free in __uprobe_unregister+0x210/0x260 kernel/events/uprobes.c:1087
> Read of size 8 at addr ffff888025a498b8 by task syz-executor380/5333
>
> CPU: 2 UID: 0 PID: 5333 Comm: syz-executor380 Not tainted 6.11.0-rc2-syzkaller-00027-g6a0e38264012 #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:93 [inline]
>  dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:119
>  print_address_description mm/kasan/report.c:377 [inline]
>  print_report+0xc3/0x620 mm/kasan/report.c:488
>  kasan_report+0xd9/0x110 mm/kasan/report.c:601
>  consumer_del kernel/events/uprobes.c:772 [inline]
>  __uprobe_unregister+0x210/0x260 kernel/events/uprobes.c:1087
>  uprobe_unregister+0x45/0x70 kernel/events/uprobes.c:1111
>  bpf_uprobe_unregister+0xfb/0x1d0 kernel/trace/bpf_trace.c:3187
>  bpf_uprobe_multi_link_release+0x6d/0x180 kernel/trace/bpf_trace.c:3197
>  bpf_link_free+0x12c/0x2b0 kernel/bpf/syscall.c:3067
>  bpf_link_put_direct kernel/bpf/syscall.c:3107 [inline]
>  bpf_link_release+0x63/0x80 kernel/bpf/syscall.c:3114
>  __fput+0x408/0xbb0 fs/file_table.c:422
>  task_work_run+0x14e/0x250 kernel/task_work.c:228
>  exit_task_work include/linux/task_work.h:40 [inline]
>  do_exit+0xaa3/0x2bb0 kernel/exit.c:882
>  do_group_exit+0xd3/0x2a0 kernel/exit.c:1031
>  __do_sys_exit_group kernel/exit.c:1042 [inline]
>  __se_sys_exit_group kernel/exit.c:1040 [inline]
>  __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1040
>  x64_sys_call+0x14a9/0x16a0 arch/x86/include/generated/asm/syscalls_64.h:232
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f4aa48570e9
> Code: Unable to access opcode bytes at 0x7f4aa48570bf.
> RSP: 002b:00007ffc0345d048 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f4aa48570e9
> RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
> RBP: 00007f4aa48ca350 R08: ffffffffffffffb8 R09: 00007f4aa48c0038
> R10: 0000000000000001 R11: 0000000000000246 R12: 00007f4aa48ca350
> R13: 0000000000000000 R14: 00007f4aa48cada0 R15: 00007f4aa48211a0
>  </TASK>
>
> Allocated by task 5333:
>  kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
>  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
>  poison_kmalloc_redzone mm/kasan/common.c:370 [inline]
>  __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:387
>  kasan_kmalloc include/linux/kasan.h:211 [inline]
>  __do_kmalloc_node mm/slub.c:4158 [inline]
>  __kmalloc_node_noprof+0x211/0x430 mm/slub.c:4164
>  __kvmalloc_node_noprof+0x9d/0x1a0 mm/util.c:650
>  kvmalloc_array_node_noprof include/linux/slab.h:833 [inline]
>  bpf_uprobe_multi_link_attach+0x45d/0xe20 kernel/trace/bpf_trace.c:3439
>  link_create kernel/bpf/syscall.c:5319 [inline]
>  __sys_bpf+0x41ff/0x4a20 kernel/bpf/syscall.c:5780
>  __do_sys_bpf kernel/bpf/syscall.c:5817 [inline]
>  __se_sys_bpf kernel/bpf/syscall.c:5815 [inline]
>  __x64_sys_bpf+0x78/0xc0 kernel/bpf/syscall.c:5815
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> Freed by task 5333:
>  kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
>  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
>  kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:579
>  poison_slab_object+0xf7/0x160 mm/kasan/common.c:240
>  __kasan_slab_free+0x32/0x50 mm/kasan/common.c:256
>  kasan_slab_free include/linux/kasan.h:184 [inline]
>  slab_free_hook mm/slub.c:2252 [inline]
>  slab_free mm/slub.c:4473 [inline]
>  kfree+0x12a/0x3b0 mm/slub.c:4594
>  kvfree+0x47/0x50 mm/util.c:696
>  bpf_uprobe_multi_link_attach+0xaae/0xe20 kernel/trace/bpf_trace.c:3500
>  link_create kernel/bpf/syscall.c:5319 [inline]
>  __sys_bpf+0x41ff/0x4a20 kernel/bpf/syscall.c:5780
>  __do_sys_bpf kernel/bpf/syscall.c:5817 [inline]
>  __se_sys_bpf kernel/bpf/syscall.c:5815 [inline]
>  __x64_sys_bpf+0x78/0xc0 kernel/bpf/syscall.c:5815
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> The buggy address belongs to the object at ffff888025a49880
>  which belongs to the cache kmalloc-64 of size 64
> The buggy address is located 56 bytes inside of
>  freed 64-byte region [ffff888025a49880, ffff888025a498c0)
>
> The buggy address belongs to the physical page:
> page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x25a49
> flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
> page_type: 0xfdffffff(slab)
> raw: 00fff00000000000 ffff8880158428c0 dead000000000100 dead000000000122
> raw: 0000000000000000 0000000080200020 00000001fdffffff 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 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 11, tgid 11 (kworker/u32:0), ts 16060739565, free_ts 16025939467
>  set_page_owner include/linux/page_owner.h:32 [inline]
>  post_alloc_hook+0x2d1/0x350 mm/page_alloc.c:1493
>  prep_new_page mm/page_alloc.c:1501 [inline]
>  get_page_from_freelist+0x1351/0x2e50 mm/page_alloc.c:3442
>  __alloc_pages_noprof+0x22b/0x2460 mm/page_alloc.c:4700
>  __alloc_pages_node_noprof include/linux/gfp.h:269 [inline]
>  alloc_pages_node_noprof include/linux/gfp.h:296 [inline]
>  alloc_slab_page+0x4e/0xf0 mm/slub.c:2321
>  allocate_slab mm/slub.c:2484 [inline]
>  new_slab+0x84/0x260 mm/slub.c:2537
>  ___slab_alloc+0xdac/0x1870 mm/slub.c:3723
>  __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3813
>  __slab_alloc_node mm/slub.c:3866 [inline]
>  slab_alloc_node mm/slub.c:4025 [inline]
>  __kmalloc_cache_node_noprof+0xf1/0x350 mm/slub.c:4197
>  kmalloc_node_noprof include/linux/slab.h:704 [inline]
>  __get_vm_area_node+0xe1/0x2d0 mm/vmalloc.c:3109
>  __vmalloc_node_range_noprof+0x276/0x1520 mm/vmalloc.c:3801
>  alloc_thread_stack_node kernel/fork.c:313 [inline]
>  dup_task_struct kernel/fork.c:1113 [inline]
>  copy_process+0x2f3b/0x8de0 kernel/fork.c:2204
>  kernel_clone+0xfd/0x980 kernel/fork.c:2781
>  user_mode_thread+0xb4/0xf0 kernel/fork.c:2859
>  call_usermodehelper_exec_work kernel/umh.c:172 [inline]
>  call_usermodehelper_exec_work+0xcb/0x170 kernel/umh.c:158
>  process_one_work+0x9c5/0x1b40 kernel/workqueue.c:3231
>  process_scheduled_works kernel/workqueue.c:3312 [inline]
>  worker_thread+0x6c8/0xf20 kernel/workqueue.c:3390
> page last free pid 986 tgid 986 stack trace:
>  reset_page_owner include/linux/page_owner.h:25 [inline]
>  free_pages_prepare mm/page_alloc.c:1094 [inline]
>  free_unref_page+0x64a/0xe40 mm/page_alloc.c:2612
>  vfree+0x181/0x7a0 mm/vmalloc.c:3364
>  delayed_vfree_work+0x56/0x70 mm/vmalloc.c:3285
>  process_one_work+0x9c5/0x1b40 kernel/workqueue.c:3231
>  process_scheduled_works kernel/workqueue.c:3312 [inline]
>  worker_thread+0x6c8/0xf20 kernel/workqueue.c:3390
>  kthread+0x2c1/0x3a0 kernel/kthread.c:389
>  ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>
> Memory state around the buggy address:
>  ffff888025a49780: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>  ffff888025a49800: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
> >ffff888025a49880: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>                                         ^
>  ffff888025a49900: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>  ffff888025a49980: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
> ==================================================================
>
>
> ---
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