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Date:   Wed, 17 Feb 2021 18:10:02 +0000
From:   Will Deacon <will@kernel.org>
To:     Andrey Ryabinin <arbn@yandex-team.com>
Cc:     Joerg Roedel <joro@8bytes.org>, iommu@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, Qian Cai <cai@lca.pw>,
        valesini@yandex-team.ru, stable@vger.kernel.org
Subject: Re: [PATCH] iommu/amd: Fix sleeping in atomic in
 increase_address_space()
Message-ID: <20210217181002.GC4304@willie-the-truck>
References: <20210217143004.19165-1-arbn@yandex-team.com>
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On Wed, Feb 17, 2021 at 05:30:04PM +0300, Andrey Ryabinin wrote:
> increase_address_space() calls get_zeroed_page(gfp) under spin_lock with
> disabled interrupts. gfp flags passed to increase_address_space() may allow
> sleeping, so it comes to this:
> 
>  BUG: sleeping function called from invalid context at mm/page_alloc.c:4342
>  in_atomic(): 1, irqs_disabled(): 1, pid: 21555, name: epdcbbf1qnhbsd8
> 
>  Call Trace:
>   dump_stack+0x66/0x8b
>   ___might_sleep+0xec/0x110
>   __alloc_pages_nodemask+0x104/0x300
>   get_zeroed_page+0x15/0x40
>   iommu_map_page+0xdd/0x3e0
>   amd_iommu_map+0x50/0x70
>   iommu_map+0x106/0x220
>   vfio_iommu_type1_ioctl+0x76e/0x950 [vfio_iommu_type1]
>   do_vfs_ioctl+0xa3/0x6f0
>   ksys_ioctl+0x66/0x70
>   __x64_sys_ioctl+0x16/0x20
>   do_syscall_64+0x4e/0x100
>   entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> Fix this by moving get_zeroed_page() out of spin_lock/unlock section.
> 
> Fixes: 754265bcab ("iommu/amd: Fix race in increase_address_space()")
> Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com>
> Cc: <stable@vger.kernel.org>
> ---
>  drivers/iommu/amd/iommu.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)

Acked-by: Will Deacon <will@kernel.org>

Will