From: Minchan Kim <minchan@kernel.org>
To: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Cc: akpm@linux-foundation.org, mhocko@kernel.org,
peterz@infradead.org, kirill@shutemov.name, ak@linux.intel.com,
dave@stgolabs.net, jack@suse.cz,
Matthew Wilcox <willy@infradead.org>,
benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
hpa@zytor.com, Will Deacon <will.deacon@arm.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
kemi.wang@intel.com, sergey.senozhatsky.work@gmail.com,
Daniel Jordan <daniel.m.jordan@oracle.com>,
David Rientjes <rientjes@google.com>,
Jerome Glisse <jglisse@redhat.com>,
Ganesh Mahendran <opensource.ganesh@gmail.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
haren@linux.vnet.ibm.com, khandual@linux.vnet.ibm.com,
npiggin@gmail.com, bsingharora@gmail.com,
paulmck@linux.vnet.ibm.com, Tim Chen <tim.c.chen@linux.intel.com>,
linuxppc-dev@lists.ozlabs.org, x86@kernel.org
Subject: Re: [PATCH v10 09/25] mm: protect VMA modifications using VMA sequence count
Date: Mon, 23 Apr 2018 16:19:41 +0900 [thread overview]
Message-ID: <20180423071941.GD114098@rodete-desktop-imager.corp.google.com> (raw)
In-Reply-To: <1523975611-15978-10-git-send-email-ldufour@linux.vnet.ibm.com>
On Tue, Apr 17, 2018 at 04:33:15PM +0200, Laurent Dufour wrote:
> The VMA sequence count has been introduced to allow fast detection of
> VMA modification when running a page fault handler without holding
> the mmap_sem.
>
> This patch provides protection against the VMA modification done in :
> - madvise()
> - mpol_rebind_policy()
> - vma_replace_policy()
> - change_prot_numa()
> - mlock(), munlock()
> - mprotect()
> - mmap_region()
> - collapse_huge_page()
> - userfaultd registering services
>
> In addition, VMA fields which will be read during the speculative fault
> path needs to be written using WRITE_ONCE to prevent write to be split
> and intermediate values to be pushed to other CPUs.
>
> Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
> ---
> fs/proc/task_mmu.c | 5 ++++-
> fs/userfaultfd.c | 17 +++++++++++++----
> mm/khugepaged.c | 3 +++
> mm/madvise.c | 6 +++++-
> mm/mempolicy.c | 51 ++++++++++++++++++++++++++++++++++-----------------
> mm/mlock.c | 13 ++++++++-----
> mm/mmap.c | 22 +++++++++++++---------
> mm/mprotect.c | 4 +++-
> mm/swap_state.c | 8 ++++++--
> 9 files changed, 89 insertions(+), 40 deletions(-)
>
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index c486ad4b43f0..aeb417f28839 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -1136,8 +1136,11 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
> goto out_mm;
> }
> for (vma = mm->mmap; vma; vma = vma->vm_next) {
> - vma->vm_flags &= ~VM_SOFTDIRTY;
> + vm_write_begin(vma);
> + WRITE_ONCE(vma->vm_flags,
> + vma->vm_flags & ~VM_SOFTDIRTY);
> vma_set_page_prot(vma);
> + vm_write_end(vma);
trivial:
I think It's tricky to maintain that VMA fields to be read during SPF should be
(READ|WRITE_ONCE). I think we need some accessor to read/write them rather than
raw accessing like like vma_set_page_prot. Maybe spf prefix would be helpful.
vma_spf_set_value(vma, vm_flags, val);
We also add some markers in vm_area_struct's fileds to indicate that
people shouldn't access those fields directly.
Just a thought.
> }
> downgrade_write(&mm->mmap_sem);
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index fe079756bb18..8a8a402ed59f 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -575,6 +575,10 @@ static unsigned long swapin_nr_pages(unsigned long offset)
> * the readahead.
> *
> * Caller must hold down_read on the vma->vm_mm if vmf->vma is not NULL.
> + * This is needed to ensure the VMA will not be freed in our back. In the case
> + * of the speculative page fault handler, this cannot happen, even if we don't
> + * hold the mmap_sem. Callees are assumed to take care of reading VMA's fields
I guess reader would be curious on *why* is safe with SPF.
Comment about the why could be helpful for reviewer.
> + * using READ_ONCE() to read consistent values.
> */
> struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
> struct vm_fault *vmf)
> @@ -668,9 +672,9 @@ static inline void swap_ra_clamp_pfn(struct vm_area_struct *vma,
> unsigned long *start,
> unsigned long *end)
> {
> - *start = max3(lpfn, PFN_DOWN(vma->vm_start),
> + *start = max3(lpfn, PFN_DOWN(READ_ONCE(vma->vm_start)),
> PFN_DOWN(faddr & PMD_MASK));
> - *end = min3(rpfn, PFN_DOWN(vma->vm_end),
> + *end = min3(rpfn, PFN_DOWN(READ_ONCE(vma->vm_end)),
> PFN_DOWN((faddr & PMD_MASK) + PMD_SIZE));
> }
>
> --
> 2.7.4
>
next prev parent reply other threads:[~2018-04-23 7:19 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-17 14:33 [PATCH v10 00/25] Speculative page faults Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 01/25] mm: introduce CONFIG_SPECULATIVE_PAGE_FAULT Laurent Dufour
2018-04-23 5:58 ` Minchan Kim
2018-04-23 15:10 ` Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 02/25] x86/mm: define ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT Laurent Dufour
2018-05-08 11:04 ` Punit Agrawal
2018-05-14 14:47 ` Laurent Dufour
2018-05-14 15:05 ` Punit Agrawal
2018-04-17 14:33 ` [PATCH v10 03/25] powerpc/mm: set ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 04/25] mm: prepare for FAULT_FLAG_SPECULATIVE Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 05/25] mm: introduce pte_spinlock " Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 06/25] mm: make pte_unmap_same compatible with SPF Laurent Dufour
2018-04-23 6:31 ` Minchan Kim
2018-04-30 14:07 ` Laurent Dufour
2018-05-01 13:04 ` Minchan Kim
2018-05-10 16:15 ` vinayak menon
2018-05-14 15:09 ` Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 07/25] mm: introduce INIT_VMA() Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 08/25] mm: VMA sequence count Laurent Dufour
2018-04-23 6:42 ` Minchan Kim
2018-04-30 15:14 ` Laurent Dufour
2018-05-01 13:16 ` Minchan Kim
2018-05-03 14:45 ` Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 09/25] mm: protect VMA modifications using " Laurent Dufour
2018-04-23 7:19 ` Minchan Kim [this message]
2018-05-14 15:25 ` Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 10/25] mm: protect mremap() against SPF hanlder Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 11/25] mm: protect SPF handler against anon_vma changes Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 12/25] mm: cache some VMA fields in the vm_fault structure Laurent Dufour
2018-04-23 7:42 ` Minchan Kim
2018-05-03 12:25 ` Laurent Dufour
2018-05-03 15:42 ` Minchan Kim
2018-05-04 9:10 ` Laurent Dufour
2018-05-08 10:56 ` Minchan Kim
2018-04-17 14:33 ` [PATCH v10 13/25] mm/migrate: Pass vm_fault pointer to migrate_misplaced_page() Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 14/25] mm: introduce __lru_cache_add_active_or_unevictable Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 15/25] mm: introduce __vm_normal_page() Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 16/25] mm: introduce __page_add_new_anon_rmap() Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 17/25] mm: protect mm_rb tree with a rwlock Laurent Dufour
2018-04-30 18:47 ` Punit Agrawal
2018-05-02 6:37 ` Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 18/25] mm: provide speculative fault infrastructure Laurent Dufour
2018-05-15 13:09 ` vinayak menon
2018-05-15 14:07 ` Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 19/25] mm: adding speculative page fault failure trace events Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 20/25] perf: add a speculative page fault sw event Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 21/25] perf tools: add support for the SPF perf event Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 22/25] mm: speculative page fault handler return VMA Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 23/25] mm: add speculative page fault vmstats Laurent Dufour
2018-05-16 2:50 ` Ganesh Mahendran
2018-05-16 6:42 ` Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 24/25] x86/mm: add speculative pagefault handling Laurent Dufour
2018-04-30 18:43 ` Punit Agrawal
2018-05-03 14:59 ` Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 25/25] powerpc/mm: add speculative page fault Laurent Dufour
2018-05-02 14:17 ` [PATCH v10 00/25] Speculative page faults Punit Agrawal
2018-05-02 14:45 ` Laurent Dufour
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