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From: Catalin Marinas <catalin.marinas@arm.com>
To: Jianyong Wu <jianyong.wu@arm.com>
Cc: will@kernel.org, anshuman.khandual@arm.com,
	akpm@linux-foundation.org, david@redhat.com,
	quic_qiancai@quicinc.com, ardb@kernel.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, gshan@redhat.com,
	justin.he@arm.com, nd@arm.com
Subject: Re: [PATCH v3] arm64/mm: avoid fixmap race condition when create pud mapping
Date: Wed, 5 Jan 2022 18:03:57 +0000	[thread overview]
Message-ID: <YdXdjcJ7jbnkFsqp@arm.com> (raw)
In-Reply-To: <20211216082812.165387-1-jianyong.wu@arm.com>

On Thu, Dec 16, 2021 at 04:28:12PM +0800, Jianyong Wu wrote:
> The 'fixmap' is a global resource and is used recursively by
> create pud mapping(), leading to a potential race condition in the
> presence of a concurrent call to alloc_init_pud():
> 
> kernel_init thread                          virtio-mem workqueue thread
> ==================                          ===========================
> 
>   alloc_init_pud(...)                       alloc_init_pud(...)
>   pudp = pud_set_fixmap_offset(...)         pudp = pud_set_fixmap_offset(...)
>   READ_ONCE(*pudp)
>   pud_clear_fixmap(...)
>                                             READ_ONCE(*pudp) // CRASH!
> 
> As kernel may sleep during creating pud mapping, introduce a mutex lock to
> serialise use of the fixmap entries by alloc_init_pud().
> 
> Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>

I tried to queue this patch but with certain configurations it doesn't
boot under Qemu. Starting from defconfig, update .config with (I had
this in one of my build scripts):

$ ./scripts/config \
		-e DEBUG_KERNEL \
		-e DEBUG_PAGEALLOC \
		-e DEBUG_PAGEALLOC_ENABLE_DEFAULT \
		-e DEBUG_WX \
		-e DEBUG_SET_MODULE_RONX \
		-e DEBUG_ALIGN_RODATA \
		-e ARM64_PTDUMP_DEBUGFS \
		-e DEBUG_OBJECTS \
		-e DEBUG_OBJECTS_FREE \
		-e DEBUG_OBJECTS_TIMERS \
		-e DEBUG_KOBJECT_RELEASE \
		-e DEBUG_LOCKING_API_SELFTESTS \
		-e DEBUG_PREEMPT \
		-e DEBUG_TIMEKEEPING \
		-e DEBUG_VM \
		-e DEBUG_VM_VMACACHE \
		-e DEBUG_VM_RB \
		-e DEBUG_VM_PGFLAGS \
		-e DEBUG_VIRTUAL \
		-e DEBUG_LIST \
		-e DEBUG_PI_LIST \
		-e DEBUG_SG \
		-e PROVE_LOCKING \
		-e DEBUG_RT_MUTEXES \
		-e DEBUG_ATOMIC_SLEEP \
		-e ATOMIC64_SELFTEST

It stop after exiting the EFI boot services. I did not have time to
debug.

-- 
Catalin

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com>
To: Jianyong Wu <jianyong.wu@arm.com>
Cc: will@kernel.org, anshuman.khandual@arm.com,
	akpm@linux-foundation.org, david@redhat.com,
	quic_qiancai@quicinc.com, ardb@kernel.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, gshan@redhat.com,
	justin.he@arm.com, nd@arm.com
Subject: Re: [PATCH v3] arm64/mm: avoid fixmap race condition when create pud mapping
Date: Wed, 5 Jan 2022 18:03:57 +0000	[thread overview]
Message-ID: <YdXdjcJ7jbnkFsqp@arm.com> (raw)
In-Reply-To: <20211216082812.165387-1-jianyong.wu@arm.com>

On Thu, Dec 16, 2021 at 04:28:12PM +0800, Jianyong Wu wrote:
> The 'fixmap' is a global resource and is used recursively by
> create pud mapping(), leading to a potential race condition in the
> presence of a concurrent call to alloc_init_pud():
> 
> kernel_init thread                          virtio-mem workqueue thread
> ==================                          ===========================
> 
>   alloc_init_pud(...)                       alloc_init_pud(...)
>   pudp = pud_set_fixmap_offset(...)         pudp = pud_set_fixmap_offset(...)
>   READ_ONCE(*pudp)
>   pud_clear_fixmap(...)
>                                             READ_ONCE(*pudp) // CRASH!
> 
> As kernel may sleep during creating pud mapping, introduce a mutex lock to
> serialise use of the fixmap entries by alloc_init_pud().
> 
> Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>

I tried to queue this patch but with certain configurations it doesn't
boot under Qemu. Starting from defconfig, update .config with (I had
this in one of my build scripts):

$ ./scripts/config \
		-e DEBUG_KERNEL \
		-e DEBUG_PAGEALLOC \
		-e DEBUG_PAGEALLOC_ENABLE_DEFAULT \
		-e DEBUG_WX \
		-e DEBUG_SET_MODULE_RONX \
		-e DEBUG_ALIGN_RODATA \
		-e ARM64_PTDUMP_DEBUGFS \
		-e DEBUG_OBJECTS \
		-e DEBUG_OBJECTS_FREE \
		-e DEBUG_OBJECTS_TIMERS \
		-e DEBUG_KOBJECT_RELEASE \
		-e DEBUG_LOCKING_API_SELFTESTS \
		-e DEBUG_PREEMPT \
		-e DEBUG_TIMEKEEPING \
		-e DEBUG_VM \
		-e DEBUG_VM_VMACACHE \
		-e DEBUG_VM_RB \
		-e DEBUG_VM_PGFLAGS \
		-e DEBUG_VIRTUAL \
		-e DEBUG_LIST \
		-e DEBUG_PI_LIST \
		-e DEBUG_SG \
		-e PROVE_LOCKING \
		-e DEBUG_RT_MUTEXES \
		-e DEBUG_ATOMIC_SLEEP \
		-e ATOMIC64_SELFTEST

It stop after exiting the EFI boot services. I did not have time to
debug.

-- 
Catalin

  parent reply	other threads:[~2022-01-05 18:05 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-16  8:28 [PATCH v3] arm64/mm: avoid fixmap race condition when create pud mapping Jianyong Wu
2021-12-16  8:28 ` Jianyong Wu
2021-12-16 15:19 ` David Hildenbrand
2021-12-16 15:19   ` David Hildenbrand
2021-12-17  9:30 ` Mark Rutland
2021-12-17  9:30   ` Mark Rutland
2021-12-17 10:09   ` Jianyong Wu
2021-12-17 10:09     ` Jianyong Wu
2022-01-05 18:03 ` Catalin Marinas [this message]
2022-01-05 18:03   ` Catalin Marinas
2022-01-06 10:13   ` Jianyong Wu
2022-01-06 10:13     ` Jianyong Wu
2022-01-06 15:56     ` Catalin Marinas
2022-01-06 15:56       ` Catalin Marinas
2022-01-07  9:10       ` Jianyong Wu
2022-01-07  9:10         ` Jianyong Wu
2022-01-07 10:42         ` Catalin Marinas
2022-01-07 10:42           ` Catalin Marinas
2022-01-26  4:20           ` Justin He
2022-01-26  4:20             ` Justin He
2022-01-26  8:36             ` Ard Biesheuvel
2022-01-26  8:36               ` Ard Biesheuvel
2022-01-26 10:09               ` Jianyong Wu
2022-01-26 10:09                 ` Jianyong Wu
2022-01-26 10:12                 ` Ard Biesheuvel
2022-01-26 10:12                   ` Ard Biesheuvel
2022-01-26 10:17                   ` David Hildenbrand
2022-01-26 10:17                     ` David Hildenbrand
2022-01-26 10:28                     ` Jianyong Wu
2022-01-26 10:28                       ` Jianyong Wu
2022-01-26 10:30                       ` David Hildenbrand
2022-01-26 10:30                         ` David Hildenbrand
2022-01-26 10:31                         ` David Hildenbrand
2022-01-26 10:31                           ` David Hildenbrand
2022-01-27  6:24                           ` Jianyong Wu
2022-01-27  6:24                             ` Jianyong Wu
2022-01-27 12:22                             ` David Hildenbrand
2022-01-27 12:22                               ` David Hildenbrand
2022-01-27 12:34                               ` Catalin Marinas
2022-01-27 12:34                                 ` Catalin Marinas
2022-01-31  8:13                                 ` Jianyong Wu
2022-01-31  8:13                                   ` Jianyong Wu
2022-01-31  8:10                               ` Jianyong Wu
2022-01-31  8:10                                 ` Jianyong Wu
2022-01-27  1:31               ` Justin He
2022-01-27  1:31                 ` Justin He
2022-01-07 10:53         ` Catalin Marinas
2022-01-07 10:53           ` Catalin Marinas

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