f011c9cf04: BUG:KASAN:slab-out-of-bounds_in_io_sq_offload_create

Hello,

kernel test robot noticed "BUG:KASAN:slab-out-of-bounds_in_io_sq_offload_create" on:

commit: f011c9cf04c06f16b24f583d313d3c012e589e50 ("io_uring/sqpoll: do not allow pinning outside of cpuset")
https://git.kernel.org/cgit/linux/kernel/git/axboe/linux-block.git for-6.12/io_uring

[test failed on linux-next/master 57f962b956f1d116cd64d5c406776c4975de549d]

in testcase: trinity
version:
with following parameters:

	runtime: 300s
	group: group-02
	nr_groups: 5

compiler: gcc-12
test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G

(please refer to attached dmesg/kmsg for entire log/backtrace)

+-------------------------------------------------------+------------+------------+
|                                                       | 0e0bcf07ec | f011c9cf04 |
+-------------------------------------------------------+------------+------------+
| BUG:KASAN:slab-use-after-free_in_io_sq_offload_create | 0          | 3          |
| BUG:KASAN:slab-out-of-bounds_in_io_sq_offload_create  | 0          | 2          |
+-------------------------------------------------------+------------+------------+

If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <[email protected]>
| Closes: https://lore.kernel.org/oe-lkp/[email protected]

[ 155.627997][ T6168] BUG: KASAN: slab-out-of-bounds in io_sq_offload_create (arch/x86/include/asm/bitops.h:227 arch/x86/include/asm/bitops.h:239 include/asm-generic/bitops/instrumented-non-atomic.h:142 include/linux/cpumask.h:562 io_uring/sqpoll.c:469) 
[  155.628787][ T6168] Read of size 8 at addr ffff888138ecf948 by task trinity-c3/6168
[  155.629542][ T6168]
[  155.629806][ T6168] CPU: 1 UID: 4294967291 PID: 6168 Comm: trinity-c3 Not tainted 6.11.0-rc5-00027-gf011c9cf04c0 #1 074b2dc9794d1910767b5e24d1a9cb7061a66647
[  155.631255][ T6168] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
[  155.632276][ T6168] Call Trace:
[  155.632627][ T6168]  <TASK>
[ 155.632952][ T6168] dump_stack_lvl (lib/dump_stack.c:122) 
[ 155.633418][ T6168] print_address_description+0x51/0x3a0 
[ 155.634147][ T6168] ? io_sq_offload_create (arch/x86/include/asm/bitops.h:227 arch/x86/include/asm/bitops.h:239 include/asm-generic/bitops/instrumented-non-atomic.h:142 include/linux/cpumask.h:562 io_uring/sqpoll.c:469) 
[ 155.634671][ T6168] print_report (mm/kasan/report.c:489) 
[ 155.635119][ T6168] ? lock_acquired (include/trace/events/lock.h:85 kernel/locking/lockdep.c:6039) 
[ 155.635596][ T6168] ? kasan_addr_to_slab (include/linux/mm.h:1283 mm/kasan/../slab.h:206 mm/kasan/common.c:38) 
[ 155.636243][ T6168] ? io_sq_offload_create (arch/x86/include/asm/bitops.h:227 arch/x86/include/asm/bitops.h:239 include/asm-generic/bitops/instrumented-non-atomic.h:142 include/linux/cpumask.h:562 io_uring/sqpoll.c:469) 
[ 155.636890][ T6168] kasan_report (mm/kasan/report.c:603) 
[ 155.637320][ T6168] ? io_sq_offload_create (arch/x86/include/asm/bitops.h:227 arch/x86/include/asm/bitops.h:239 include/asm-generic/bitops/instrumented-non-atomic.h:142 include/linux/cpumask.h:562 io_uring/sqpoll.c:469) 
[ 155.637873][ T6168] kasan_check_range (mm/kasan/generic.c:183 mm/kasan/generic.c:189) 
[ 155.638384][ T6168] io_sq_offload_create (arch/x86/include/asm/bitops.h:227 arch/x86/include/asm/bitops.h:239 include/asm-generic/bitops/instrumented-non-atomic.h:142 include/linux/cpumask.h:562 io_uring/sqpoll.c:469) 
[ 155.638921][ T6168] ? __pfx_io_sq_offload_create (io_uring/sqpoll.c:413) 
[ 155.639501][ T6168] ? __lock_acquire (kernel/locking/lockdep.c:5142) 
[ 155.640040][ T6168] ? io_pages_map (include/linux/gfp.h:269 include/linux/gfp.h:296 include/linux/gfp.h:313 io_uring/memmap.c:28 io_uring/memmap.c:72) 
[ 155.640495][ T6168] ? io_allocate_scq_urings (io_uring/io_uring.c:3441) 
[ 155.641079][ T6168] io_uring_create (io_uring/io_uring.c:3606) 
[ 155.641591][ T6168] io_uring_setup (io_uring/io_uring.c:3715) 
[ 155.642185][ T6168] ? __pfx_io_uring_setup (io_uring/io_uring.c:3693) 
[ 155.642698][ T6168] ? do_int80_emulation (arch/x86/include/asm/irqflags.h:42 arch/x86/include/asm/irqflags.h:97 arch/x86/entry/common.c:251) 
[ 155.643206][ T6168] do_int80_emulation (arch/x86/entry/common.c:165 arch/x86/entry/common.c:253) 
[ 155.643675][ T6168] asm_int80_emulation (arch/x86/include/asm/idtentry.h:626) 
[  155.644159][ T6168] RIP: 0033:0x407ebc
[ 155.644532][ T6168] Code: 83 c0 01 41 89 80 40 30 00 00 8b 44 24 04 4c 89 d1 48 8b 54 24 08 4c 89 de 4c 89 e7 55 41 50 41 51 41 52 41 53 4c 89 cd cd 80 <41> 5b 41 5a 41 59 41 58 5d 48 3d 7a ff ff ff 49 89 c4 0f 87 5c 01
All code
========
   0:	83 c0 01             	add    $0x1,%eax
   3:	41 89 80 40 30 00 00 	mov    %eax,0x3040(%r8)
   a:	8b 44 24 04          	mov    0x4(%rsp),%eax
   e:	4c 89 d1             	mov    %r10,%rcx
  11:	48 8b 54 24 08       	mov    0x8(%rsp),%rdx
  16:	4c 89 de             	mov    %r11,%rsi
  19:	4c 89 e7             	mov    %r12,%rdi
  1c:	55                   	push   %rbp
  1d:	41 50                	push   %r8
  1f:	41 51                	push   %r9
  21:	41 52                	push   %r10
  23:	41 53                	push   %r11
  25:	4c 89 cd             	mov    %r9,%rbp
  28:	cd 80                	int    $0x80
  2a:*	41 5b                	pop    %r11		<-- trapping instruction
  2c:	41 5a                	pop    %r10
  2e:	41 59                	pop    %r9
  30:	41 58                	pop    %r8
  32:	5d                   	pop    %rbp
  33:	48 3d 7a ff ff ff    	cmp    $0xffffffffffffff7a,%rax
  39:	49 89 c4             	mov    %rax,%r12
  3c:	0f                   	.byte 0xf
  3d:	87                   	.byte 0x87
  3e:	5c                   	pop    %rsp
  3f:	01                   	.byte 0x1

Code starting with the faulting instruction
===========================================

   0:	41 5b                	pop    %r11
   2:	41 5a                	pop    %r10
   4:	41 59                	pop    %r9
   6:	41 58                	pop    %r8
   8:	5d                   	pop    %rbp
   9:	48 3d 7a ff ff ff    	cmp    $0xffffffffffffff7a,%rax
   f:	49 89 c4             	mov    %rax,%r12
  12:	0f                   	.byte 0xf
  13:	87                   	.byte 0x87
  14:	5c                   	pop    %rsp
  15:	01                   	.byte 0x1
[  155.650354][ T6168] RSP: 002b:00007ffe588726a8 EFLAGS: 00000202 ORIG_RAX: 00000000000001a9
[  155.651160][ T6168] RAX: ffffffffffffffda RBX: 000000000000018b RCX: 0000000000000001
[  155.651928][ T6168] RDX: 0000000000000020 RSI: ff39a6338351dabb RDI: 0000004801000022
[  155.652658][ T6168] RBP: 00000000000000d8 R08: 00007f75264d9000 R09: 00000000000000d8
[  155.653402][ T6168] R10: 0000000000000001 R11: ff39a6338351dabb R12: 0000004801000022
[  155.654296][ T6168] R13: 00007f75261cd058 R14: 0000000014055850 R15: 00007f75261cd000
[  155.655144][ T6168]  </TASK>
[  155.655463][ T6168]
[  155.655702][ T6168] Allocated by task 5605:
[ 155.656127][ T6168] kasan_save_stack (mm/kasan/common.c:48) 
[ 155.656595][ T6168] kasan_save_track (arch/x86/include/asm/current.h:49 mm/kasan/common.c:60 mm/kasan/common.c:69) 
[ 155.657087][ T6168] __kasan_slab_alloc (mm/kasan/common.c:312 mm/kasan/common.c:338) 
[ 155.657583][ T6168] kmem_cache_alloc_noprof (mm/slub.c:3988 mm/slub.c:4037 mm/slub.c:4044) 
[ 155.658217][ T6168] getname_flags (fs/namei.c:139) 
[ 155.658665][ T6168] user_path_at (fs/namei.c:3002) 
[ 155.659099][ T6168] path_getxattr (fs/xattr.c:785) 
[ 155.659569][ T6168] do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83) 
[ 155.660020][ T6168] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) 
[  155.660569][ T6168]
[  155.660776][ T6168] Freed by task 5605:
[ 155.661134][ T6168] kasan_save_stack (mm/kasan/common.c:48) 
[ 155.661543][ T6168] kasan_save_track (arch/x86/include/asm/current.h:49 mm/kasan/common.c:60 mm/kasan/common.c:69) 
[ 155.662064][ T6168] kasan_save_free_info (mm/kasan/generic.c:582) 
[ 155.662570][ T6168] __kasan_slab_free (mm/kasan/common.c:264) 
[ 155.663054][ T6168] kmem_cache_free (mm/slub.c:4473 mm/slub.c:4548) 
[ 155.663559][ T6168] user_path_at (fs/namei.c:3006) 
[ 155.664016][ T6168] path_getxattr (fs/xattr.c:785) 
[ 155.664454][ T6168] do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83) 
[ 155.664866][ T6168] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) 
[  155.665459][ T6168]
[  155.665709][ T6168] The buggy address belongs to the object at ffff888138ece600
[  155.665709][ T6168]  which belongs to the cache names_cache of size 4096
[  155.667216][ T6168] The buggy address is located 840 bytes to the right of
[  155.667216][ T6168]  allocated 4096-byte region [ffff888138ece600, ffff888138ecf600)
[  155.668597][ T6168]
[  155.668840][ T6168] The buggy address belongs to the physical page:
[  155.669458][ T6168] page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x138ec8
[  155.670449][ T6168] head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
[  155.671298][ T6168] flags: 0x8000000000000040(head|zone=2)
[  155.671866][ T6168] page_type: 0xfdffffff(slab)
[  155.672341][ T6168] raw: 8000000000000040 ffff888101a588c0 ffffea0004e34a00 dead000000000002
[  155.673187][ T6168] raw: 0000000000000000 0000000000070007 00000001fdffffff 0000000000000000
[  155.674122][ T6168] head: 8000000000000040 ffff888101a588c0 ffffea0004e34a00 dead000000000002
[  155.675017][ T6168] head: 0000000000000000 0000000000070007 00000001fdffffff 0000000000000000
[  155.675912][ T6168] head: 8000000000000003 ffffea0004e3b201 ffffffffffffffff 0000000000000000
[  155.676727][ T6168] head: 0000000000000008 0000000000000000 00000000ffffffff 0000000000000000
[  155.677541][ T6168] page dumped because: kasan: bad access detected
[  155.678288][ T6168] page_owner tracks the page as allocated
[  155.678859][ T6168] page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1391, tgid 1391 (grep), ts 35826248170, free_ts 0
[ 155.680744][ T6168] post_alloc_hook (include/linux/page_owner.h:32 mm/page_alloc.c:1493) 
[ 155.681229][ T6168] get_page_from_freelist (mm/page_alloc.c:1503 mm/page_alloc.c:3439) 
[ 155.681767][ T6168] __alloc_pages_noprof (mm/page_alloc.c:4695) 
[ 155.682356][ T6168] allocate_slab (include/linux/gfp.h:269 include/linux/gfp.h:296 mm/slub.c:2321 mm/slub.c:2484) 
[ 155.682811][ T6168] ___slab_alloc (mm/slub.c:3724 (discriminator 3)) 
[ 155.683285][ T6168] __slab_alloc+0x58/0xc0 
[ 155.683836][ T6168] kmem_cache_alloc_noprof (mm/slub.c:3866 mm/slub.c:4025 mm/slub.c:4044) 
[ 155.684381][ T6168] getname_flags (fs/namei.c:139) 
[ 155.684823][ T6168] do_sys_openat2 (fs/open.c:1410) 
[ 155.685268][ T6168] __x64_sys_openat (fs/open.c:1442) 
[ 155.685770][ T6168] do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83) 
[ 155.686312][ T6168] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) 
[  155.686902][ T6168] page_owner free stack trace missing
[  155.687448][ T6168]
[  155.687683][ T6168] Memory state around the buggy address:
[  155.688227][ T6168]  ffff888138ecf800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[  155.688998][ T6168]  ffff888138ecf880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[  155.689839][ T6168] >ffff888138ecf900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[  155.690685][ T6168]                                               ^
[  155.691299][ T6168]  ffff888138ecf980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[  155.692085][ T6168]  ffff888138ecfa00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[  155.692848][ T6168] ==================================================================
[  155.693783][ T6168] Disabling lock debugging due to kernel taint
[  158.741439][    C1] workqueue: pcpu_balance_workfn hogged CPU for >10000us 4 times, consider switching to WQ_UNBOUND

The kernel config and materials to reproduce are available at:
https://download.01.org/0day-ci/archive/20240916/[email protected]

0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

The fix for the cpusets dropped checking if the value was sane to begin with... I've fixed it up with the patch below.

commit 827e3ea024a4facf1d6c8969ae95de939890039e

Author: Jens Axboe <[email protected]>
Date:   Mon Sep 16 02:58:06 2024 -0600

    io_uring/sqpoll: retain test for whether the CPU is valid
    
    A recent commit ensured that SQPOLL cannot be setup with a CPU that
    isn't in the current tasks cpuset, but it also dropped testing whether
    the CPU is valid in the first place. Without that, if a task passes in
    a CPU value that is too high, the following KASAN splat can get
    triggered:
    
    BUG: KASAN: stack-out-of-bounds in io_sq_offload_create+0x858/0xaa4
    Read of size 8 at addr ffff800089bc7b90 by task wq-aff.t/1391
    
    CPU: 4 UID: 1000 PID: 1391 Comm: wq-aff.t Not tainted 6.11.0-rc7-00227-g371c468f4db6 #7080
    Hardware name: linux,dummy-virt (DT)
    Call trace:
     dump_backtrace.part.0+0xcc/0xe0
     show_stack+0x14/0x1c
     dump_stack_lvl+0x58/0x74
     print_report+0x16c/0x4c8
     kasan_report+0x9c/0xe4
     __asan_report_load8_noabort+0x1c/0x24
     io_sq_offload_create+0x858/0xaa4
     io_uring_setup+0x1394/0x17c4
     __arm64_sys_io_uring_setup+0x6c/0x180
     invoke_syscall+0x6c/0x260
     el0_svc_common.constprop.0+0x158/0x224
     do_el0_svc+0x3c/0x5c
     el0_svc+0x34/0x70
     el0t_64_sync_handler+0x118/0x124
     el0t_64_sync+0x168/0x16c
    
    The buggy address belongs to stack of task wq-aff.t/1391
     and is located at offset 48 in frame:
     io_sq_offload_create+0x0/0xaa4
    
    This frame has 1 object:
     [32, 40) 'allowed_mask'
    
    The buggy address belongs to the virtual mapping at
     [ffff800089bc0000, ffff800089bc9000) created by:
     kernel_clone+0x124/0x7e0
    
    The buggy address belongs to the physical page:
    page: refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff0000d740af80 pfn:0x11740a
    memcg:ffff0000c2706f02
    flags: 0xbffe00000000000(node=0|zone=2|lastcpupid=0x1fff)
    raw: 0bffe00000000000 0000000000000000 dead000000000122 0000000000000000
    raw: ffff0000d740af80 0000000000000000 00000001ffffffff ffff0000c2706f02
    page dumped because: kasan: bad access detected
    
    Memory state around the buggy address:
     ffff800089bc7a80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
     ffff800089bc7b00: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1
    >ffff800089bc7b80: 00 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
                             ^
     ffff800089bc7c00: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1
     ffff800089bc7c80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f3
    
    Reported-by: kernel test robot <[email protected]>
    Closes: https://lore.kernel.org/oe-lkp/[email protected]
    Fixes: f011c9cf04c0 ("io_uring/sqpoll: do not allow pinning outside of cpuset")
    Signed-off-by: Jens Axboe <[email protected]>

index 272df9d00f45..7adfcf6818ff 100644
@@ -465,6 +465,8 @@ __cold int io_sq_offload_create(struct io_ring_ctx *ctx,
 			int cpu = p->sq_thread_cpu;
 
 			ret = -EINVAL;
+			if (cpu >= nr_cpu_ids || !cpu_online(cpu))
+				goto err_sqpoll;
 			cpuset_cpus_allowed(current, &allowed_mask);
 			if (!cpumask_test_cpu(cpu, &allowed_mask))
 				goto err_sqpoll;

Jens Axboe

Thanks for fixing. While we are at it, I noticed that putting the cpumask on the stack is discouraged. We should better allocate it like in my other patches. Shall I send a fixup patch?

Best regards,
Felix

Siemens AG, Technology
Linux Expert Center

Yes probably not a bad idea, some systems configure with a large number of possible CPUs.

Jens Axboe