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

From: syzbot
Date: Wed Apr 17 2024 - 22:39:11 EST


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