Re: [syzbot] [mm?] BUG: unable to handle kernel paging request in __pte_offset_map_lock
From: Hugh Dickins
Date: Thu Nov 16 2023 - 02:40:27 EST
On Thu, 26 Oct 2023, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 78124b0c1d10 Merge branch 'for-next/core' into for-kernelci
> git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
> console output: https://syzkaller.appspot.com/x/log.txt?x=111b0e71680000
> kernel config: https://syzkaller.appspot.com/x/.config?x=f27cd6e68911e026
> dashboard link: https://syzkaller.appspot.com/bug?extid=89edd67979b52675ddec
> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> userspace arch: arm64
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16b8e671680000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=125a9df5680000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/bd512de820ae/disk-78124b0c.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/a47a437b1d4f/vmlinux-78124b0c.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/3ae8b966bcd7/Image-78124b0c.gz.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+89edd67979b52675ddec@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> Unable to handle kernel paging request at virtual address dfff800000000004
> KASAN: null-ptr-deref in range [0x0000000000000020-0x0000000000000027]
> Mem abort info:
> ESR = 0x0000000096000005
> EC = 0x25: DABT (current EL), IL = 32 bits
> SET = 0, FnV = 0
> EA = 0, S1PTW = 0
> FSC = 0x05: level 1 translation fault
> Data abort info:
> ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000
> CM = 0, WnR = 0, TnD = 0, TagAccess = 0
> GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
> [dfff800000000004] address between user and kernel address ranges
> Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP
> Modules linked in:
> CPU: 0 PID: 7952 Comm: syz-executor682 Not tainted 6.6.0-rc6-syzkaller-g78124b0c1d10 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
> pstate: 804000c5 (Nzcv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : __lock_acquire+0x104/0x75e8 kernel/locking/lockdep.c:5004
> lr : lock_acquire+0x23c/0x71c kernel/locking/lockdep.c:5753
> sp : ffff800098f26d40
> x29: ffff800098f27000 x28: ffff8000808df4bc x27: ffff7000131e4e18
> x26: 1ffff00011c340b9 x25: 0000000000000000 x24: 0000000000000000
> x23: ffff7000131e4dd0 x22: 0000000000000000 x21: 0000000000000000
> x20: 0000000000000000 x19: 0000000000000022 x18: ffff800098f27750
> x17: 0000ffff833dafff x16: ffff80008a632120 x15: 0000000000000001
> x14: ffff80008e1a05d0 x13: ffff800098f26e80 x12: dfff800000000000
> x11: ffff800080319468 x10: ffff80008e1a05cc x9 : 00000000000000f3
> x8 : 0000000000000004 x7 : ffff8000808df4bc x6 : 0000000000000000
> x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000
> x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000022
> Call trace:
> __lock_acquire+0x104/0x75e8 kernel/locking/lockdep.c:5004
> lock_acquire+0x23c/0x71c kernel/locking/lockdep.c:5753
> __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
> _raw_spin_lock+0x48/0x60 kernel/locking/spinlock.c:154
> spin_lock include/linux/spinlock.h:351 [inline]
> __pte_offset_map_lock+0x154/0x360 mm/pgtable-generic.c:373
> pte_offset_map_lock include/linux/mm.h:2939 [inline]
> filemap_map_pages+0x698/0x11f0 mm/filemap.c:3582
> do_fault_around mm/memory.c:4525 [inline]
> do_read_fault mm/memory.c:4558 [inline]
> do_fault mm/memory.c:4705 [inline]
> do_pte_missing mm/memory.c:3669 [inline]
> handle_pte_fault mm/memory.c:4978 [inline]
> __handle_mm_fault mm/memory.c:5119 [inline]
> handle_mm_fault+0x326c/0x49fc mm/memory.c:5284
> faultin_page mm/gup.c:956 [inline]
> __get_user_pages+0x3e0/0xa24 mm/gup.c:1239
> populate_vma_page_range+0x254/0x328 mm/gup.c:1666
> __mm_populate+0x240/0x3d8 mm/gup.c:1775
> mm_populate include/linux/mm.h:3305 [inline]
> vm_mmap_pgoff+0x2bc/0x3d4 mm/util.c:551
> ksys_mmap_pgoff+0xd0/0x5b0 mm/mmap.c:1400
> __do_sys_mmap arch/arm64/kernel/sys.c:28 [inline]
> __se_sys_mmap arch/arm64/kernel/sys.c:21 [inline]
> __arm64_sys_mmap+0xf8/0x110 arch/arm64/kernel/sys.c:21
> __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
> invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51
> el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136
> do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155
> el0_svc+0x54/0x158 arch/arm64/kernel/entry-common.c:678
> el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:696
> el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:595
> Code: b006f948 b943a108 34000208 d343fe68 (386c6908)
> ---[ end trace 0000000000000000 ]---
> ----------------
> Code disassembly (best guess):
> 0: b006f948 adrp x8, 0xdf29000
> 4: b943a108 ldr w8, [x8, #928]
> 8: 34000208 cbz w8, 0x48
> c: d343fe68 lsr x8, x19, #3
> * 10: 386c6908 ldrb w8, [x8, x12] <-- trapping instruction
>
>
> ---
> 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@xxxxxxxxxxxxxxxx.
>
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>
> If the bug is already fixed, 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
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>
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>
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>
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> #syz undup
Okay, let's try again by replying to the full orginal report
(see thread Matthew linked to for discussion leading to this):
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git b85ea95d086471afb4ad062012a4d73cd328fa86
Subject: [PATCH] mm/pgtable: smp_rmb() to match smp_wmb() in pmd_install()
Not-Yet-Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
---
mm/memory.c | 2 ++
mm/pgtable-generic.c | 5 +++++
2 files changed, 7 insertions(+)
diff --git a/mm/memory.c b/mm/memory.c
index 1f18ed4a5497..8939357f1509 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -425,6 +425,8 @@ void pmd_install(struct mm_struct *mm, pmd_t *pmd, pgtable_t *pte)
* being the notable exception) will already guarantee loads are
* seen in-order. See the alpha page table accessors for the
* smp_rmb() barriers in page table walking code.
+ *
+ * See __pte_offset_map() for the smp_rmb() at the pte level.
*/
smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */
pmd_populate(mm, pmd, *pte);
diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index 4fcd959dcc4d..3330b666e9c3 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -297,6 +297,11 @@ pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp)
pmd_clear_bad(pmd);
goto nomap;
}
+ /*
+ * Pair with the smp_wmb() in pmd_install(): make sure that the
+ * page table lock and page table contents are visibly initialized.
+ */
+ smp_rmb();
return __pte_map(&pmdval, addr);
nomap:
rcu_read_unlock();
--
2.35.3