Message-ID: <e9f2e391-5c83-481a-9fa4-727c25922f1c@redhat.com>
Date: Fri, 1 Aug 2025 12:14:42 +0200
From: David Hildenbrand <david@...hat.com>
To: syzbot <syzbot+99d4fec338b62b703891@...kaller.appspotmail.com>,
 Liam.Howlett@...cle.com, akpm@...ux-foundation.org, andrii@...nel.org,
 ast@...nel.org, bpf@...r.kernel.org, daniel@...earbox.net,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 lorenzo.stoakes@...cle.com, mhocko@...e.com, rppt@...nel.org,
 surenb@...gle.com, syzkaller-bugs@...glegroups.com, vbabka@...e.cz,
 Sasha Levin <sashal@...nel.org>
Subject: Re: [syzbot] [mm?] WARNING in trace_suspend_resume

On 01.08.25 12:08, syzbot wrote:
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    f2d282e1dfb3 Merge tag 'bitmap-for-6.17' of https://github..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=11709cf0580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=c686e0c98d241433
> dashboard link: https://syzkaller.appspot.com/bug?extid=99d4fec338b62b703891
> compiler:       arm-linux-gnueabi-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> userspace arch: arm
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15e0e2a2580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12a439bc580000
> 
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/98a89b9f34e4/non_bootable_disk-f2d282e1.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/25cab46afcee/vmlinux-f2d282e1.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/77cd04442f1b/zImage-f2d282e1.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+99d4fec338b62b703891@...kaller.appspotmail.com
> 
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 4155 at mm/highmem.c:622 kunmap_local_indexed+0x20c/0x224 mm/highmem.c:622
> Modules linked in:
> Kernel panic - not syncing: kernel: panic_on_warn set ...
> CPU: 0 UID: 0 PID: 4155 Comm: syz.1.17 Not tainted 6.16.0-syzkaller #0 PREEMPT
> Hardware name: ARM-Versatile Express
> Call trace:
> [<80201a24>] (dump_backtrace) from [<80201b20>] (show_stack+0x18/0x1c arch/arm/kernel/traps.c:257)
>   r7:00000000 r6:8281f77c r5:00000000 r4:8224bc00
> [<80201b08>] (show_stack) from [<8021fb00>] (__dump_stack lib/dump_stack.c:94 [inline])
> [<80201b08>] (show_stack) from [<8021fb00>] (dump_stack_lvl+0x54/0x7c lib/dump_stack.c:120)
> [<8021faac>] (dump_stack_lvl) from [<8021fb40>] (dump_stack+0x18/0x1c lib/dump_stack.c:129)
>   r5:00000000 r4:82a76d18
> [<8021fb28>] (dump_stack) from [<80202624>] (vpanic+0x10c/0x360 kernel/panic.c:440)
> [<80202518>] (vpanic) from [<802028ac>] (trace_suspend_resume+0x0/0xd8 kernel/panic.c:574)
>   r7:804be014
> [<80202878>] (panic) from [<802548c4>] (check_panic_on_warn kernel/panic.c:333 [inline])
> [<80202878>] (panic) from [<802548c4>] (get_taint+0x0/0x1c kernel/panic.c:328)
>   r3:8280c684 r2:00000001 r1:822326d8 r0:8223a0a0
> [<80254850>] (check_panic_on_warn) from [<80254a28>] (__warn+0x80/0x188 kernel/panic.c:845)
> [<802549a8>] (__warn) from [<80254ca8>] (warn_slowpath_fmt+0x178/0x1f4 kernel/panic.c:872)
>   r8:00000009 r7:82266338 r6:df985d14 r5:840d5400 r4:00000000
> [<80254b34>] (warn_slowpath_fmt) from [<804be014>] (kunmap_local_indexed+0x20c/0x224 mm/highmem.c:622)
>   r10:00000000 r9:ded86c30 r8:deb6caa4 r7:00a00000 r6:00000003 r5:840d5400
>   r4:ffefd000
> [<804bde08>] (kunmap_local_indexed) from [<8053ace8>] (__kunmap_local include/linux/highmem-internal.h:102 [inline])
> [<804bde08>] (kunmap_local_indexed) from [<8053ace8>] (move_pages_pte mm/userfaultfd.c:1457 [inline])
> [<804bde08>] (kunmap_local_indexed) from [<8053ace8>] (move_pages+0xb1c/0x1a00 mm/userfaultfd.c:1860)
>   r7:00a00000 r6:00000000 r5:8490d6ac r4:ffefb000
> [<8053a1cc>] (move_pages) from [<805c401c>] (userfaultfd_move fs/userfaultfd.c:1923 [inline])
> [<8053a1cc>] (move_pages) from [<805c401c>] (userfaultfd_ioctl+0x1254/0x2408 fs/userfaultfd.c:2046)
>   r10:8425d6c0 r9:df985e98 r8:00000001 r7:21000000 r6:00000000 r5:20000040
>   r4:8486d000
> [<805c2dc8>] (userfaultfd_ioctl) from [<8056c4d4>] (vfs_ioctl fs/ioctl.c:51 [inline])
> [<805c2dc8>] (userfaultfd_ioctl) from [<8056c4d4>] (do_vfs_ioctl fs/ioctl.c:552 [inline])
> [<805c2dc8>] (userfaultfd_ioctl) from [<8056c4d4>] (__do_sys_ioctl fs/ioctl.c:596 [inline])
> [<805c2dc8>] (userfaultfd_ioctl) from [<8056c4d4>] (sys_ioctl+0x130/0xba0 fs/ioctl.c:584)
>   r10:840d5400 r9:00000003 r8:8572d780 r7:20000040 r6:8572d780 r5:00000000
>   r4:c028aa05
> [<8056c3a4>] (sys_ioctl) from [<80200060>] (ret_fast_syscall+0x0/0x1c arch/arm/mm/proc-v7.S:67)
> Exception stack(0xdf985fa8 to 0xdf985ff0)
> 5fa0:                   00000000 00000000 00000003 c028aa05 20000040 00000000
> 5fc0: 00000000 00000000 002f6300 00000036 00000000 002f62d4 00000938 00000000
> 5fe0: 7eb28780 7eb28770 000193dc 001321f0
>   r10:00000036 r9:840d5400 r8:8020029c r7:00000036 r6:002f6300 r5:00000000
>   r4:00000000
> Rebooting in 86400 seconds..

Probably fixed by

	https://lore.kernel.org/r/20250731144431.773923-1-sashal@kernel.org/

#syz test

--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -1453,10 +1453,15 @@ static int move_pages_pte(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd,
  		folio_unlock(src_folio);
  		folio_put(src_folio);
  	}
-	if (dst_pte)
-		pte_unmap(dst_pte);
+	/*
+	 * Unmap in reverse order (LIFO) to maintain proper kmap_local
+	 * index ordering when CONFIG_HIGHPTE is enabled. We mapped dst_pte
+	 * first, then src_pte, so we must unmap src_pte first, then dst_pte.
+	 */
  	if (src_pte)
  		pte_unmap(src_pte);
+	if (dst_pte)
+		pte_unmap(dst_pte);
  	mmu_notifier_invalidate_range_end(&range);
  	if (si)
  		put_swap_device(si);
-- 
2.39.5



-- 
Cheers,

David / dhildenb

Powered by blists - more mailing lists