From: Andy Lutomirski <luto@kernel.org>
To: Joerg Roedel <joro@8bytes.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>, Joerg Roedel <jroedel@suse.de>
Subject: Re: [PATCH 3/3] mm/vmalloc: Sync unmappings in vunmap_page_range()
Date: Wed, 17 Jul 2019 14:24:09 -0700 [thread overview]
Message-ID: <CALCETrXfCbajLhUixKNaMfFw91gzoQzt__faYLwyBqA3eAbQVA@mail.gmail.com> (raw)
In-Reply-To: <20190717071439.14261-4-joro@8bytes.org>
On Wed, Jul 17, 2019 at 12:14 AM Joerg Roedel <joro@8bytes.org> wrote:
>
> From: Joerg Roedel <jroedel@suse.de>
>
> On x86-32 with PTI enabled, parts of the kernel page-tables
> are not shared between processes. This can cause mappings in
> the vmalloc/ioremap area to persist in some page-tables
> after the regions is unmapped and released.
>
> When the region is re-used the processes with the old
> mappings do not fault in the new mappings but still access
> the old ones.
>
> This causes undefined behavior, in reality often data
> corruption, kernel oopses and panics and even spontaneous
> reboots.
>
> Fix this problem by activly syncing unmaps in the
> vmalloc/ioremap area to all page-tables in the system.
>
> References: https://bugzilla.suse.com/show_bug.cgi?id=1118689
> Fixes: 5d72b4fba40ef ('x86, mm: support huge I/O mapping capability I/F')
> Signed-off-by: Joerg Roedel <jroedel@suse.de>
> ---
> mm/vmalloc.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 4fa8d84599b0..322b11a374fd 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -132,6 +132,8 @@ static void vunmap_page_range(unsigned long addr, unsigned long end)
> continue;
> vunmap_p4d_range(pgd, addr, next);
> } while (pgd++, addr = next, addr != end);
> +
> + vmalloc_sync_all();
> }
I'm confused. Shouldn't the code in _vm_unmap_aliases handle this?
As it stands, won't your patch hurt performance on x86_64? If x86_32
is a special snowflake here, maybe flush_tlb_kernel_range() should
handle this?
Even if your patch is correct, a comment would be nice
next prev parent reply other threads:[~2019-07-17 21:24 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-17 7:14 [PATCH 0/3 v2] Sync unmappings in vmalloc/ioremap areas Joerg Roedel
2019-07-17 7:14 ` [PATCH 1/3] x86/mm: Check for pfn instead of page in vmalloc_sync_one() Joerg Roedel
2019-07-17 7:14 ` [PATCH 2/3] x86/mm: Sync also unmappings " Joerg Roedel
2019-07-17 21:06 ` Dave Hansen
2019-07-18 8:44 ` Joerg Roedel
2019-07-17 21:43 ` Thomas Gleixner
2019-07-18 8:46 ` Joerg Roedel
2019-07-18 9:04 ` Thomas Gleixner
2019-07-18 9:25 ` Joerg Roedel
2019-07-19 14:01 ` Joerg Roedel
2019-07-19 21:10 ` Thomas Gleixner
2019-07-17 7:14 ` [PATCH 3/3] mm/vmalloc: Sync unmappings in vunmap_page_range() Joerg Roedel
2019-07-17 21:24 ` Andy Lutomirski [this message]
2019-07-18 9:17 ` Joerg Roedel
2019-07-18 19:04 ` Andy Lutomirski
2019-07-19 12:21 ` Joerg Roedel
2019-07-19 12:24 ` Andy Lutomirski
2019-07-19 13:00 ` Joerg Roedel
-- strict thread matches above, loose matches on Subject: below --
2019-07-19 18:46 [PATCH 0/3 v3] Sync unmappings in vmalloc/ioremap areas Joerg Roedel
2019-07-19 18:46 ` [PATCH 3/3] mm/vmalloc: Sync unmappings in vunmap_page_range() Joerg Roedel
2019-07-22 8:11 ` Joerg Roedel
2019-07-22 8:19 ` Thomas Gleixner
2019-07-22 8:29 ` Joerg Roedel
2019-07-15 11:02 [PATCH 0/3] Sync unmappings in vmalloc/ioremap areas Joerg Roedel
2019-07-15 11:02 ` [PATCH 3/3] mm/vmalloc: Sync unmappings in vunmap_page_range() Joerg Roedel
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