[syzbot] [mm?] KASAN: slab-use-after-free Read in hugetlb_fault

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9ed46da14b9b Add linux-next specific files for 20240412
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=14a4d74d180000
kernel config: https://syzkaller.appspot.com/x/.config?x=7ea0abc478c49859
dashboard link: https://syzkaller.appspot.com/bug?extid=7fd4b85697bcf2a9daa2
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=1011afeb180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16f89857180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/fc649744d68c/disk-9ed46da1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/11eab7b9945d/vmlinux-9ed46da1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e7885afd198d/bzImage-9ed46da1.xz

The issue was bisected to:

commit 7c43a553792a1701affeef20959dfb2ccb26dcee
Author: Vishal Moola (Oracle) <vishal...@gmail.com>
Date: Wed Feb 21 23:47:32 2024 +0000

hugetlb: allow faults to be handled under the VMA lock

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=105bf935180000
final oops: https://syzkaller.appspot.com/x/report.txt?x=125bf935180000
console output: https://syzkaller.appspot.com/x/log.txt?x=145bf935180000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7fd4b8...@syzkaller.appspotmail.com
Fixes: 7c43a553792a ("hugetlb: allow faults to be handled under the VMA lock")

==================================================================
BUG: KASAN: slab-use-after-free in __vma_shareable_lock include/linux/hugetlb.h:1273 [inline]
BUG: KASAN: slab-use-after-free in hugetlb_vma_unlock_read mm/hugetlb.c:281 [inline]
BUG: KASAN: slab-use-after-free in hugetlb_no_page mm/hugetlb.c:6383 [inline]
BUG: KASAN: slab-use-after-free in hugetlb_fault+0x27b9/0x3910 mm/hugetlb.c:6487
Read of size 8 at addr ffff8880163ac400 by task syz-executor233/5335

CPU: 0 PID: 5335 Comm: syz-executor233 Not tainted 6.9.0-rc3-next-20240412-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
print_address_description mm/kasan/report.c:377 [inline]
print_report+0x169/0x550 mm/kasan/report.c:488
kasan_report+0x143/0x180 mm/kasan/report.c:601
__vma_shareable_lock include/linux/hugetlb.h:1273 [inline]
hugetlb_vma_unlock_read mm/hugetlb.c:281 [inline]
hugetlb_no_page mm/hugetlb.c:6383 [inline]
hugetlb_fault+0x27b9/0x3910 mm/hugetlb.c:6487
handle_mm_fault+0x18e8/0x1bb0 mm/memory.c:5701
do_user_addr_fault arch/x86/mm/fault.c:1368 [inline]
handle_page_fault arch/x86/mm/fault.c:1511 [inline]
exc_page_fault+0x459/0x900 arch/x86/mm/fault.c:1569
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0033:0x7f6a2c7e7fcb
Code: bf a9 01 00 00 e8 15 4d 03 00 48 83 f8 ff 0f 84 99 fd ff ff 48 89 05 34 c1 0b 00 48 83 c4 08 5b 5d c3 66 0f 6f 05 c5 b0 08 00 <0f> 29 04 25 00 00 00 20 66 0f 6f 05 c5 b0 08 00 0f 11 04 25 0c 00
RSP: 002b:00007f6a2c7b6160 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 00007f6a2c8a6318 RCX: 00007f6a2c81ccd9
RDX: fe319eacbf5b3dac RSI: 0000000000000000 RDI: 00007f6a2c7b65a0
RBP: 00007f6a2c8a6310 R08: 0000000000000000 R09: 00007f6a2c7b66c0
R10: 00007f6a2c7b66c0 R11: 0000000000000246 R12: 00007f6a2c8a631c
R13: 000000000000006e R14: 00007ffee83e4b30 R15: 00007ffee83e4c18
</TASK>

Allocated by task 5328:
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:312 [inline]
__kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:338
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook mm/slub.c:3897 [inline]
slab_alloc_node mm/slub.c:3957 [inline]
kmem_cache_alloc_noprof+0x135/0x290 mm/slub.c:3964
vm_area_alloc+0x24/0x1d0 kernel/fork.c:467
mmap_region+0xc20/0x2030 mm/mmap.c:2852
do_mmap+0x8ad/0xfa0 mm/mmap.c:1387
vm_mmap_pgoff+0x1dd/0x3d0 mm/util.c:573
ksys_mmap_pgoff+0x544/0x720 mm/mmap.c:1433
do_syscall_x64 arch/x86/entry/common.c:74 [inline]
do_syscall_64+0xfa/0x250 arch/x86/entry/common.c:105
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 51:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579
poison_slab_object+0xe0/0x150 mm/kasan/common.c:240
__kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
kasan_slab_free include/linux/kasan.h:184 [inline]
slab_free_hook mm/slub.c:2190 [inline]
slab_free mm/slub.c:4393 [inline]
kmem_cache_free+0x145/0x340 mm/slub.c:4468
rcu_do_batch kernel/rcu/tree.c:2565 [inline]
rcu_core+0xafd/0x1830 kernel/rcu/tree.c:2839
__do_softirq+0x2c6/0x980 kernel/softirq.c:554

Last potentially related work creation:
kasan_save_stack+0x3f/0x60 mm/kasan/common.c:47
__kasan_record_aux_stack+0xac/0xc0 mm/kasan/generic.c:541
__call_rcu_common kernel/rcu/tree.c:3102 [inline]
call_rcu+0x167/0xa70 kernel/rcu/tree.c:3206
remove_vma mm/mmap.c:148 [inline]
remove_mt mm/mmap.c:2334 [inline]
do_vmi_align_munmap+0x155c/0x18c0 mm/mmap.c:2677
do_vmi_munmap+0x24e/0x2d0 mm/mmap.c:2741
mmap_region+0x729/0x2030 mm/mmap.c:2792
do_mmap+0x8ad/0xfa0 mm/mmap.c:1387
vm_mmap_pgoff+0x1dd/0x3d0 mm/util.c:573
ksys_mmap_pgoff+0x544/0x720 mm/mmap.c:1433
do_syscall_x64 arch/x86/entry/common.c:74 [inline]
do_syscall_64+0xfa/0x250 arch/x86/entry/common.c:105
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880163ac3e0
which belongs to the cache vm_area_struct of size 184
The buggy address is located 32 bytes inside of
freed 184-byte region [ffff8880163ac3e0, ffff8880163ac498)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x163ac
flags: 0xfff80000000000(node=0|zone=1|lastcpupid=0xfff)
page_type: 0xffffefff(slab)
raw: 00fff80000000000 ffff8880162a7b40 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000100010 00000001ffffefff 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 4760, tgid 1563571937 (dhcpcd-run-hook), ts 4760, free_ts 31621429750
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1474
prep_new_page mm/page_alloc.c:1482 [inline]
get_page_from_freelist+0x2ce2/0x2d90 mm/page_alloc.c:3444
__alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4702
__alloc_pages_node_noprof include/linux/gfp.h:244 [inline]
alloc_pages_node_noprof include/linux/gfp.h:271 [inline]
alloc_slab_page+0x5f/0x120 mm/slub.c:2259
allocate_slab+0x5a/0x2e0 mm/slub.c:2422
new_slab mm/slub.c:2475 [inline]
___slab_alloc+0xcd1/0x14b0 mm/slub.c:3624
__slab_alloc+0x58/0xa0 mm/slub.c:3714
__slab_alloc_node mm/slub.c:3767 [inline]
slab_alloc_node mm/slub.c:3945 [inline]
kmem_cache_alloc_noprof+0x1c1/0x290 mm/slub.c:3964
vm_area_alloc+0x24/0x1d0 kernel/fork.c:467
__bprm_mm_init fs/exec.c:261 [inline]
bprm_mm_init fs/exec.c:395 [inline]
alloc_bprm+0x37a/0xa40 fs/exec.c:1599
do_execveat_common+0x1b3/0x700 fs/exec.c:1949
do_execve fs/exec.c:2072 [inline]
__do_sys_execve fs/exec.c:2148 [inline]
__se_sys_execve fs/exec.c:2143 [inline]
__x64_sys_execve+0x92/0xb0 fs/exec.c:2143
do_syscall_x64 arch/x86/entry/common.c:74 [inline]
do_syscall_64+0xfa/0x250 arch/x86/entry/common.c:105
entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 4759 tgid 4759 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1094 [inline]
free_unref_page+0xd22/0xea0 mm/page_alloc.c:2607
tlb_batch_list_free mm/mmu_gather.c:159 [inline]
tlb_finish_mmu+0x11f/0x200 mm/mmu_gather.c:468
exit_mmap+0x44f/0xc80 mm/mmap.c:3325
__mmput+0x115/0x3c0 kernel/fork.c:1346
exit_mm+0x220/0x310 kernel/exit.c:569
do_exit+0x99e/0x27e0 kernel/exit.c:865
do_group_exit+0x207/0x2c0 kernel/exit.c:1027
__do_sys_exit_group kernel/exit.c:1038 [inline]
__se_sys_exit_group kernel/exit.c:1036 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1036
do_syscall_x64 arch/x86/entry/common.c:74 [inline]
do_syscall_64+0xfa/0x250 arch/x86/entry/common.c:105
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
ffff8880163ac300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8880163ac380: 00 00 00 00 fc fc fc fc fc fc fc fc fa fb fb fb
>ffff8880163ac400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880163ac480: fb fb fb fc fc fc fc fc fc fc fc fa fb fb fb fb
ffff8880163ac500: 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 syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

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If you want to undo deduplication, reply with:
#syz undup

[Hillf Danton]

On Wed, 17 Apr 2024 15:30:26 -0700

> syzbot found the following issue on:
>
> HEAD commit: 9ed46da14b9b Add linux-next specific files for 20240412
> git tree: linux-next

> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16f89857180000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git 9ed46da14b9b

--- x/mm/hugetlb.c
+++ y/mm/hugetlb.c
@@ -6251,6 +6251,12 @@ static vm_fault_t hugetlb_no_page(struct
VM_UFFD_MISSING);
}

+ if (!(vma->vm_flags & VM_MAYSHARE)) {
+ ret = vmf_anon_prepare(vmf);
+ if (unlikely(ret))
+ goto out;
+ }
+
folio = alloc_hugetlb_folio(vma, vmf->address, 0);
if (IS_ERR(folio)) {
/*
@@ -6290,15 +6296,12 @@ static vm_fault_t hugetlb_no_page(struct
restore_reserve_on_error(h, vma, vmf->address,
folio);
folio_put(folio);
+ ret = VM_FAULT_SIGBUS;
goto out;
}
new_pagecache_folio = true;
} else {
folio_lock(folio);
-
- ret = vmf_anon_prepare(vmf);
- if (unlikely(ret))
- goto backout_unlocked;
anon_rmap = 1;
}
} else {
--

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING: suspicious RCU usage in __do_softirq

=============================
WARNING: suspicious RCU usage
6.9.0-rc3-next-20240412-syzkaller-dirty #0 Not tainted
-----------------------------
kernel/rcu/tree.c:276 Illegal rcu_softirq_qs() in RCU read-side critical section!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
1 lock held by ksoftirqd/0/16:
#0: ffffffff8e334060 (rcu_read_lock_sched){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
#0: ffffffff8e334060 (rcu_read_lock_sched){....}-{1:2}, at: rcu_read_lock_sched include/linux/rcupdate.h:933 [inline]
#0: ffffffff8e334060 (rcu_read_lock_sched){....}-{1:2}, at: pfn_valid include/linux/mmzone.h:2019 [inline]
#0: ffffffff8e334060 (rcu_read_lock_sched){....}-{1:2}, at: __virt_addr_valid+0x183/0x520 arch/x86/mm/physaddr.c:65

stack backtrace:
CPU: 0 PID: 16 Comm: ksoftirqd/0 Not tainted 6.9.0-rc3-next-20240412-syzkaller-dirty #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:

<IRQ>

__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114

lockdep_rcu_suspicious+0x221/0x340 kernel/locking/lockdep.c:6712
rcu_softirq_qs+0xd9/0x370 kernel/rcu/tree.c:273
__do_softirq+0x5fd/0x980 kernel/softirq.c:568
invoke_softirq kernel/softirq.c:428 [inline]
__irq_exit_rcu+0xf2/0x1c0 kernel/softirq.c:633
irq_exit_rcu+0x9/0x30 kernel/softirq.c:645
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1043
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:lock_release+0x51/0x9f0 kernel/locking/lockdep.c:5762
Code: 04 25 28 00 00 00 48 89 84 24 e0 00 00 00 49 bf 00 00 00 00 00 fc ff df 48 c7 44 24 60 b3 8a b5 41 48 c7 44 24 68 5d 09 b4 8d <48> c7 44 24 70 e0 d2 72 81 4c 8d 64 24 60 49 c1 ec 03 48 b8 f1 f1
RSP: 0018:ffffc90000157920 EFLAGS: 00000282
RAX: 1ce013f6d4eb5b00 RBX: 0000000000000001 RCX: ffff888016ec5a00
RDX: 0000000000000000 RSI: ffffffff81423eb3 RDI: ffffffff8e334060
RBP: ffffc90000157a48 R08: ffffffff81424067 R09: 1ffffffff25ee6b4
R10: dffffc0000000000 R11: fffffbfff25ee6b5 R12: 000000002524d378
R13: ffffffff81423eb3 R14: ffffffff81423eb3 R15: dffffc0000000000
rcu_lock_release include/linux/rcupdate.h:339 [inline]
rcu_read_unlock_sched include/linux/rcupdate.h:954 [inline]
pfn_valid include/linux/mmzone.h:2029 [inline]
__virt_addr_valid+0x41e/0x520 arch/x86/mm/physaddr.c:65
kasan_addr_to_slab+0xd/0x80 mm/kasan/common.c:37
__kasan_record_aux_stack+0x11/0xc0 mm/kasan/generic.c:526

__call_rcu_common kernel/rcu/tree.c:3102 [inline]
call_rcu+0x167/0xa70 kernel/rcu/tree.c:3206

context_switch kernel/sched/core.c:5412 [inline]
__schedule+0x17f0/0x4a50 kernel/sched/core.c:6746
__schedule_loop kernel/sched/core.c:6823 [inline]
schedule+0x14b/0x320 kernel/sched/core.c:6838
smpboot_thread_fn+0x61e/0xa30 kernel/smpboot.c:160
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
</TASK>
----------------
Code disassembly (best guess):
0: 04 25 add $0x25,%al
2: 28 00 sub %al,(%rax)
4: 00 00 add %al,(%rax)
6: 48 89 84 24 e0 00 00 mov %rax,0xe0(%rsp)
d: 00
e: 49 bf 00 00 00 00 00 movabs $0xdffffc0000000000,%r15
15: fc ff df
18: 48 c7 44 24 60 b3 8a movq $0x41b58ab3,0x60(%rsp)
1f: b5 41
21: 48 c7 44 24 68 5d 09 movq $0xffffffff8db4095d,0x68(%rsp)
28: b4 8d
* 2a: 48 c7 44 24 70 e0 d2 movq $0xffffffff8172d2e0,0x70(%rsp) <-- trapping instruction
31: 72 81
33: 4c 8d 64 24 60 lea 0x60(%rsp),%r12
38: 49 c1 ec 03 shr $0x3,%r12
3c: 48 rex.W
3d: b8 .byte 0xb8
3e: f1 int1
3f: f1 int1


Tested on:

commit: 9ed46da1 Add linux-next specific files for 20240412
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1260ada3180000

kernel config: https://syzkaller.appspot.com/x/.config?x=7ea0abc478c49859
dashboard link: https://syzkaller.appspot.com/bug?extid=7fd4b85697bcf2a9daa2
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=16ccb37d180000

[Hillf Danton]

On Wed, 17 Apr 2024 15:30:26 -0700

> syzbot found the following issue on:
>
> HEAD commit: 9ed46da14b9b Add linux-next specific files for 20240412
> git tree: linux-next

--- x/kernel/softirq.c
+++ y/kernel/softirq.c
@@ -564,7 +564,7 @@ restart:
}

if (!IS_ENABLED(CONFIG_PREEMPT_RT) &&
- __this_cpu_read(ksoftirqd) == current)
+ __this_cpu_read(ksoftirqd) == current && in_task())
rcu_softirq_qs();

local_irq_disable();
--

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+7fd4b8...@syzkaller.appspotmail.com

Tested on:

commit: 9ed46da1 Add linux-next specific files for 20240412
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git

console output: https://syzkaller.appspot.com/x/log.txt?x=147e17b3180000

kernel config: https://syzkaller.appspot.com/x/.config?x=7ea0abc478c49859
dashboard link: https://syzkaller.appspot.com/bug?extid=7fd4b85697bcf2a9daa2
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=16c94a53180000

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