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Date:   Thu, 11 Apr 2019 21:54:24 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     kernel test robot <lkp@intel.com>
Cc:     LKP <lkp@01.org>, linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        linux-arch@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Will Deacon <will.deacon@arm.com>
Subject: Re: 1808d65b55 ("asm-generic/tlb: Remove arch_tlb*_mmu()"):  BUG:
 KASAN: stack-out-of-bounds in __change_page_attr_set_clr
Message-ID: <20190411195424.GL14281@hirez.programming.kicks-ass.net>
References: <5cae03c4.iIPk2cWlfmzP0Zgy%lkp@intel.com>
 <20190411193906.GA12232@hirez.programming.kicks-ass.net>
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On Thu, Apr 11, 2019 at 09:39:06PM +0200, Peter Zijlstra wrote:
> I think this bisect is bad. If you look at your own logs this patch
> merely changes the failure, but doesn't make it go away.
> 
> Before this patch (in fact, before tip/core/mm entirely) the errror
> reads like the below, which suggests there is memory corruption
> somewhere, and the fingered patch just makes it trigger differently.
> 
> It would be very good to find the source of this corruption, but I'm
> fairly certain it is not here.

I went back to v4.20 to try and find a time when the below error did not
occur, but even that reliably triggers the warning.

> [   10.273617] rodata_test: all tests were successful
> [   10.275015] x86/mm: Checking user space page tables
> [   10.295444] x86/mm: Checked W+X mappings: passed, no W+X pages found.
> [   10.296334] Run /init as init process
> [   10.301465] ==================================================================
> [   10.302460] BUG: KASAN: stack-out-of-bounds in __unwind_start+0x7e/0x4fe
> [   10.303355] Write of size 88 at addr ffff8880191efa28 by task init/1
> [   10.304241]
> [   10.304455] CPU: 0 PID: 1 Comm: init Not tainted 5.1.0-rc4-00288-ga131d61b43e0-dirty #10
> [   10.305542] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
> [   10.306641] Call Trace:
> [   10.306990]  print_address_description+0x9d/0x26b
> [   10.307654]  ? __unwind_start+0x7e/0x4fe
> [   10.308222]  ? __unwind_start+0x7e/0x4fe
> [   10.308755]  __kasan_report+0x145/0x18a
> [   10.309266]  ? __unwind_start+0x7e/0x4fe
> [   10.309823]  kasan_report+0xe/0x12
> [   10.310273]  memset+0x1f/0x31
> [   10.310703]  __unwind_start+0x7e/0x4fe
> [   10.311223]  ? unwind_next_frame+0x10a9/0x10a9
> [   10.311839]  ? native_flush_tlb_one_user+0x54/0x95
> [   10.312504]  ? kasan_unpoison_shadow+0xf/0x2e
> [   10.313090]  __save_stack_trace+0x65/0xe7
> [   10.313667]  ? trace_irq_enable_rcuidle+0x21/0xf5
> [   10.314284]  ? tracer_hardirqs_on+0xb/0x1b
> [   10.314830]  ? trace_hardirqs_on+0x2c/0x37
> [   10.315369]  save_stack+0x32/0xa3
> [   10.315842]  ? __put_compound_page+0x91/0x91
> [   10.316458]  ? preempt_latency_start+0x22/0x68
> [   10.317052]  ? free_swap_cache+0x51/0xd5
> [   10.317586]  ? tlb_flush_mmu_free+0x31/0xca
> [   10.318140]  ? arch_tlb_finish_mmu+0x8c/0x112
> [   10.318759]  ? tlb_finish_mmu+0xc7/0xd6
> [   10.319298]  ? unmap_region+0x275/0x2b9
> [   10.319835]  ? special_mapping_fault+0x26d/0x26d
> [   10.320448]  ? trace_irq_disable_rcuidle+0x21/0xf5
> [   10.321085]  __kasan_slab_free+0xd3/0xf4
> [   10.321623]  ? remove_vma+0xdf/0xe7
> [   10.322105]  kmem_cache_free+0x4e/0xca
> [   10.322600]  remove_vma+0xdf/0xe7
> [   10.323038]  __do_munmap+0x72c/0x75e
> [   10.323514]  __vm_munmap+0xd0/0x135
> [   10.323980]  ? __x64_sys_brk+0x40e/0x40e
> [   10.324496]  ? trace_irq_disable_rcuidle+0x21/0xf5
> [   10.325160]  __x64_sys_munmap+0x6a/0x6f
> [   10.325670]  do_syscall_64+0x3f0/0x462
> [   10.326162]  ? syscall_return_slowpath+0x154/0x154
> [   10.326810]  ? entry_SYSCALL_64_after_hwframe+0x3e/0xbe
> [   10.327485]  ? trace_irq_disable_rcuidle+0x21/0xf5
> [   10.328153]  ? entry_SYSCALL_64_after_hwframe+0x3e/0xbe
> [   10.328873]  ? trace_hardirqs_off_caller+0x3e/0x40
> [   10.329505]  ? trace_hardirqs_off_thunk+0x1a/0x1c
> [   10.330162]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> [   10.330830] RIP: 0033:0x7efc4d707457
> [   10.331306] Code: f0 ff ff 73 01 c3 48 8d 0d 5a be 20 00 31 d2 48 29 c2 89 11 48 83 c8 ff eb eb 90 90 90 90 90 90 90 90 90 b8 0b 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8d 0d 2d be 20 00 31 d2 48 29 c2 89
> [   10.333711] RSP: 002b:00007fff973da398 EFLAGS: 00000203 ORIG_RAX: 000000000000000b
> [   10.334728] RAX: ffffffffffffffda RBX: 00007efc4d9132c8 RCX: 00007efc4d707457
> [   10.335670] RDX: 0000000000000000 RSI: 0000000000001d67 RDI: 00007efc4d90d000
> [   10.336596] RBP: 00007fff973da4f0 R08: 0000000000000007 R09: 00000000ffffffff
> [   10.337512] R10: 0000000000000000 R11: 0000000000000203 R12: 000000073dd74283
> [   10.338457] R13: 000000073db1ab4f R14: 00007efc4d909700 R15: 00007efc4d9132c8
> [   10.339373]
> [   10.339585] The buggy address belongs to the page:
> [   10.340224] page:ffff88801de82c48 count:0 mapcount:0 mapping:0000000000000000 index:0x0
> [   10.341338] flags: 0x680000000000()
> [   10.341832] raw: 0000680000000000 ffff88801de82c50 ffff88801de82c50 0000000000000000
> [   10.342846] raw: 0000000000000000 0000000000000000 00000000ffffffff
> [   10.343679] page dumped because: kasan: bad access detected
> [   10.344415]
> [   10.344629] Memory state around the buggy address:
> [   10.345254]  ffff8880191ef900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> [   10.346245]  ffff8880191ef980: 00 00 f1 f1 f1 f1 00 f2 f2 f2 00 00 00 00 00 00
> [   10.347217] >ffff8880191efa00: 00 00 00 00 00 f2 f2 f2 00 00 00 00 00 00 00 00
> [   10.348152]                                   ^
> [   10.348755]  ffff8880191efa80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> [   10.349698]  ffff8880191efb00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> [   10.350650] ==================================================================