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Mon, 4 May 2026 08:13:51 +0800 (CST) X-Sender: hdanton@sina.com X-Auth-ID: hdanton@sina.com Authentication-Results: sina.com; spf=none smtp.mailfrom=hdanton@sina.com; dkim=none header.i=none; dmarc=none action=none header.from=hdanton@sina.com X-SMAIL-MID: 8880276292018 X-SMAIL-UIID: 41E3D6F3D43F4283A5B5BD8EC0EE964A-20260504-081351-1 From: Hillf Danton To: syzbot Cc: Boqun Feng , linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, vbabka@kernel.org Subject: Re: [syzbot] [mm?] BUG: sleeping function called from invalid context in vma_alloc_folio_noprof (2) Date: Mon, 4 May 2026 08:13:42 +0800 Message-ID: <20260504001345.307-1-hdanton@sina.com> In-Reply-To: <69f735ce.050a0220.312cd3.0031.GAE@google.com> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit > Date: Sun, 03 May 2026 04:47:26 -0700 [thread overview] > Hello, > > syzbot found the following issue on: > > HEAD commit: dca922e019dd Merge tag 'xsa48x-7.1-tag' of git://git.kerne.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=100242ce580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=d0f0911eedbc130a > dashboard link: https://syzkaller.appspot.com/bug?extid=a21650c1666eae7b2aae > compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 > userspace arch: i386 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-dca922e0.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/1e719cb224ff/vmlinux-dca922e0.xz > kernel image: https://storage.googleapis.com/syzbot-assets/79a541b03a9e/bzImage-dca922e0.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+a21650c1666eae7b2aae@syzkaller.appspotmail.com > > BUG: sleeping function called from invalid context at ./include/linux/sched/mm.h:323 > in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 5665, name: dhcpcd-run-hook > preempt_count: 0, expected: 0 > RCU nest depth: 1, expected: 0 > 2 locks held by dhcpcd-run-hook/5665: > #0: ffff8880243d01c8 (vm_lock){++++}-{0:0}, at: lock_vma_under_rcu+0x11d/0x590 mm/mmap_lock.c:310 > #1: ffffffff8e7e52e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] > #1: ffffffff8e7e52e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] > #1: ffffffff8e7e52e0 (rcu_read_lock){....}-{1:3}, at: __pte_offset_map+0x2f/0x310 mm/pgtable-generic.c:290 > CPU: 0 UID: 0 PID: 5665 Comm: dhcpcd-run-hook Not tainted syzkaller #0 PREEMPT(full) > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 > Call Trace: > > __dump_stack lib/dump_stack.c:94 [inline] > dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 > __might_resched.cold+0x1ec/0x232 kernel/sched/core.c:9162 > might_alloc include/linux/sched/mm.h:323 [inline] > prepare_alloc_pages+0x44a/0x5f0 mm/page_alloc.c:4995 > __alloc_frozen_pages_noprof+0x19a/0x2bc0 mm/page_alloc.c:5215 > alloc_pages_mpol+0x1fb/0x540 mm/mempolicy.c:2490 > folio_alloc_mpol_noprof+0x36/0x260 mm/mempolicy.c:2509 > vma_alloc_folio_noprof+0xed/0x1d0 mm/mempolicy.c:2544 > folio_prealloc mm/memory.c:1193 [inline] > wp_page_copy mm/memory.c:3859 [inline] > do_wp_page+0x1ee1/0x4350 mm/memory.c:4320 Given pte_unmap_unlock() [1] before wp_page_copy(), the lockdep record of rcu lock above looks false positive. Baffled. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/memory.c#n4315 > handle_pte_fault mm/memory.c:6427 [inline] > __handle_mm_fault+0x1ab6/0x2a00 mm/memory.c:6549 > handle_mm_fault+0x36d/0xa20 mm/memory.c:6718 > do_user_addr_fault+0x5a3/0x12f0 arch/x86/mm/fault.c:1334 > handle_page_fault arch/x86/mm/fault.c:1474 [inline] > exc_page_fault+0x6f/0xd0 arch/x86/mm/fault.c:1527 > asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 > RIP: 0033:0x7f5a6f60980e > Code: df e8 d7 c4 ff ff 48 8d 3d 9c 92 05 00 31 c0 e8 e1 ca ff ff 95 75 24 48 8d 05 5e 9c 07 00 44 89 f2 4c 89 e6 48 89 df 48 8b 00 <83> a0 f8 02 00 00 00 e8 de eb ff ff e9 a8 00 00 00 48 85 db 0f 84 > RSP: 002b:00007ffc0b5c63f0 EFLAGS: 00010246 > RAX: 000055c4ea134910 RBX: 000055c4ea135c60 RCX: 0000000000000000 > RDX: 0000000000000000 RSI: 000055c4ea138c30 RDI: 000055c4ea135c60 > RBP: 0000000000000000 R08: 00007f5a6f5b4b60 R09: 0000000000000000 > R10: 0000000000000008 R11: 0000000000000246 R12: 000055c4ea138c30 > R13: 000055c4ea135c60 R14: 0000000000000000 R15: 0000000000000000 > > > ================================================ > WARNING: lock held when returning to user space! > syzkaller #0 Tainted: G W > ------------------------------------------------ > dhcpcd-run-hook/5665 is leaving the kernel with locks still held! > 1 lock held by dhcpcd-run-hook/5665: > #0: ffffffff8e7e52e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] > #0: ffffffff8e7e52e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] > #0: ffffffff8e7e52e0 (rcu_read_lock){....}-{1:3}, at: __pte_offset_map+0x2f/0x310 mm/pgtable-generic.c:290 > > > --- > 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 syzkaller@googlegroups.com. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > If the report is already addressed, let syzbot know by replying with: > #syz fix: exact-commit-title > > If you want to overwrite report's subsystems, reply with: > #syz set subsystems: new-subsystem > (See the list of subsystem names on the web dashboard) > > If the report is a duplicate of another one, reply with: > #syz dup: exact-subject-of-another-report > > If you want to undo deduplication, reply with: > #syz undup