* Re: [syzbot] general protection fault in try_grab_compound_head [not found] <0000000000000cafda05c639e751@google.com> @ 2021-07-03 20:24 ` syzbot 2021-07-08 13:03 ` Thomas Gleixner 0 siblings, 1 reply; 4+ messages in thread From: syzbot @ 2021-07-03 20:24 UTC (permalink / raw) To: akpm, bp, hpa, jmattson, joro, kvm, linux-kernel, linux-mm, mark.rutland, masahiroy, mingo, pbonzini, peterz, rafael.j.wysocki, rostedt, seanjc, sedat.dilek, syzkaller-bugs, tglx, vitor, vkuznets, wanpengli, will, x86 syzbot has bisected this issue to: commit 997acaf6b4b59c6a9c259740312a69ea549cc684 Author: Mark Rutland <mark.rutland@arm.com> Date: Mon Jan 11 15:37:07 2021 +0000 lockdep: report broken irq restoration bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=16fbcec4300000 start commit: 3dbdb38e Merge branch 'for-5.14' of git://git.kernel.org/p.. git tree: upstream final oops: https://syzkaller.appspot.com/x/report.txt?x=15fbcec4300000 console output: https://syzkaller.appspot.com/x/log.txt?x=11fbcec4300000 kernel config: https://syzkaller.appspot.com/x/.config?x=a1fcf15a09815757 dashboard link: https://syzkaller.appspot.com/bug?extid=a3fcd59df1b372066f5a syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11a856c4300000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1582c9d8300000 Reported-by: syzbot+a3fcd59df1b372066f5a@syzkaller.appspotmail.com Fixes: 997acaf6b4b5 ("lockdep: report broken irq restoration") For information about bisection process see: https://goo.gl/tpsmEJ#bisection ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [syzbot] general protection fault in try_grab_compound_head 2021-07-03 20:24 ` [syzbot] general protection fault in try_grab_compound_head syzbot @ 2021-07-08 13:03 ` Thomas Gleixner 2021-07-12 21:29 ` Sean Christopherson 0 siblings, 1 reply; 4+ messages in thread From: Thomas Gleixner @ 2021-07-08 13:03 UTC (permalink / raw) To: syzbot, akpm, bp, hpa, jmattson, joro, kvm, linux-kernel, linux-mm, mark.rutland, masahiroy, mingo, pbonzini, peterz, rafael.j.wysocki, rostedt, seanjc, sedat.dilek, syzkaller-bugs, vitor, vkuznets, wanpengli, will, x86 On Sat, Jul 03 2021 at 13:24, syzbot wrote: > syzbot has bisected this issue to: > > commit 997acaf6b4b59c6a9c259740312a69ea549cc684 > Author: Mark Rutland <mark.rutland@arm.com> > Date: Mon Jan 11 15:37:07 2021 +0000 > > lockdep: report broken irq restoration That's the commit which makes the underlying problem visible: raw_local_irq_restore() called with IRQs enabled and is triggered by this call chain: kvm_wait arch/x86/kernel/kvm.c:860 [inline] kvm_wait+0xc3/0xe0 arch/x86/kernel/kvm.c:837 pv_wait arch/x86/include/asm/paravirt.h:564 [inline] pv_wait_head_or_lock kernel/locking/qspinlock_paravirt.h:470 [inline] __pv_queued_spin_lock_slowpath+0x8b8/0xb40 kernel/locking/qspinlock.c:508 pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:554 [inline] queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline] queued_spin_lock include/asm-generic/qspinlock.h:85 [inline] do_raw_spin_lock+0x200/0x2b0 kernel/locking/spinlock_debug.c:113 spin_lock include/linux/spinlock.h:354 [inline] alloc_huge_page+0x2b0/0xda0 mm/hugetlb.c:2318 hugetlb_no_page mm/hugetlb.c:4323 [inline] hugetlb_fault+0xc35/0x1cd0 mm/hugetlb.c:4523 follow_hugetlb_page+0x317/0xda0 mm/hugetlb.c:4836 __get_user_pages+0x3fa/0xe30 mm/gup.c:1041 __get_user_pages_locked mm/gup.c:1256 [inline] __gup_longterm_locked+0x15f/0xc80 mm/gup.c:1667 io_sqe_buffer_register fs/io_uring.c:8462 [inline] __io_uring_register fs/io_uring.c:9901 [inline] __do_sys_io_uring_register+0xeb1/0x3350 fs/io_uring.c:10000 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Thanks, tglx ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [syzbot] general protection fault in try_grab_compound_head 2021-07-08 13:03 ` Thomas Gleixner @ 2021-07-12 21:29 ` Sean Christopherson 2021-07-13 1:08 ` Joao Martins 0 siblings, 1 reply; 4+ messages in thread From: Sean Christopherson @ 2021-07-12 21:29 UTC (permalink / raw) To: Thomas Gleixner Cc: syzbot, akpm, bp, hpa, jmattson, joro, kvm, linux-kernel, linux-mm, mark.rutland, masahiroy, mingo, pbonzini, peterz, rafael.j.wysocki, rostedt, sedat.dilek, syzkaller-bugs, vitor, vkuznets, wanpengli, will, x86 On Thu, Jul 08, 2021, Thomas Gleixner wrote: > On Sat, Jul 03 2021 at 13:24, syzbot wrote: > > syzbot has bisected this issue to: > > > > commit 997acaf6b4b59c6a9c259740312a69ea549cc684 > > Author: Mark Rutland <mark.rutland@arm.com> > > Date: Mon Jan 11 15:37:07 2021 +0000 > > > > lockdep: report broken irq restoration > > That's the commit which makes the underlying problem visible: > > raw_local_irq_restore() called with IRQs enabled > > and is triggered by this call chain: > > kvm_wait arch/x86/kernel/kvm.c:860 [inline] > kvm_wait+0xc3/0xe0 arch/x86/kernel/kvm.c:837 And the bug in kvm_wait() was fixed by commit f4e61f0c9add ("x86/kvm: Fix broken irq restoration in kvm_wait"). The bisection is bad, syzbot happened into the kvm_wait() WARN and got distracted. The original #GP looks stable, if someone from mm land has bandwidth. ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [syzbot] general protection fault in try_grab_compound_head 2021-07-12 21:29 ` Sean Christopherson @ 2021-07-13 1:08 ` Joao Martins 0 siblings, 0 replies; 4+ messages in thread From: Joao Martins @ 2021-07-13 1:08 UTC (permalink / raw) To: Sean Christopherson, Mike Kravetz Cc: syzbot, akpm, bp, hpa, jmattson, joro, kvm, linux-kernel, linux-mm, mark.rutland, masahiroy, mingo, pbonzini, peterz, rafael.j.wysocki, rostedt, sedat.dilek, syzkaller-bugs, vitor, vkuznets, wanpengli, will, x86, Thomas Gleixner On 7/12/21 10:29 PM, Sean Christopherson wrote: > On Thu, Jul 08, 2021, Thomas Gleixner wrote: >> On Sat, Jul 03 2021 at 13:24, syzbot wrote: >>> syzbot has bisected this issue to: >>> >>> commit 997acaf6b4b59c6a9c259740312a69ea549cc684 >>> Author: Mark Rutland <mark.rutland@arm.com> >>> Date: Mon Jan 11 15:37:07 2021 +0000 >>> >>> lockdep: report broken irq restoration >> >> That's the commit which makes the underlying problem visible: >> >> raw_local_irq_restore() called with IRQs enabled >> >> and is triggered by this call chain: >> >> kvm_wait arch/x86/kernel/kvm.c:860 [inline] >> kvm_wait+0xc3/0xe0 arch/x86/kernel/kvm.c:837 > > And the bug in kvm_wait() was fixed by commit f4e61f0c9add ("x86/kvm: Fix broken > irq restoration in kvm_wait"). The bisection is bad, syzbot happened into the > kvm_wait() WARN and got distracted. The original #GP looks stable, if someone > from mm land has bandwidth. > I've bisected this to (my) recent commit 82e5d378b0e47 ("mm/hugetlb: refactor subpage recording"). I have this fix below and should formally submit tomorrow after more testing. My apologies for the trouble. Joao ------>8------ Subject: mm/hugetlb: fix refs calculation from unaligned @vaddr commit 82e5d378b0e47 ("mm/hugetlb: refactor subpage recording") refactored the count of subpages but missed an edge case when @vaddr is less than a PAGE_SIZE close to vma->vm_end. It would errousnly set @refs to 0 and record_subpages_vmas() wouldn't set the pages array element to its value, consequently causing the reported #GP by syzbot. Fix it by aligning down @vaddr in @refs calculation. Reported-by: syzbot+a3fcd59df1b372066f5a@syzkaller.appspotmail.com Fixes: 82e5d378b0e47 ("mm/hugetlb: refactor subpage recording") Signed-off-by: Joao Martins <joao.m.martins@oracle.com> diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a86a58ef132d..cbc448c1a3c8 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4949,8 +4949,9 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, continue; } - refs = min3(pages_per_huge_page(h) - pfn_offset, - (vma->vm_end - vaddr) >> PAGE_SHIFT, remainder); + /* [vaddr .. vm_end] may not be aligned to PAGE_SIZE */ + refs = min3(pages_per_huge_page(h) - pfn_offset, remainder, + (vma->vm_end - ALIGN_DOWN(vaddr, PAGE_SIZE)) >> PAGE_SHIFT); if (pages || vmas) record_subpages_vmas(mem_map_offset(page, pfn_offset), ^ permalink raw reply related [flat|nested] 4+ messages in thread
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2021-07-03 20:24 ` [syzbot] general protection fault in try_grab_compound_head syzbot
2021-07-08 13:03 ` Thomas Gleixner
2021-07-12 21:29 ` Sean Christopherson
2021-07-13 1:08 ` Joao Martins
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