From: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com
commit 0a85e51d37645e9ce57e5e1a30859e07810ed07c upstream.
Patch series "thp: fix few MADV_DONTNEED races"
For MADV_DONTNEED to work properly with huge pages, it's critical to not clear pmd intermittently unless you hold down_write(mmap_sem).
Otherwise MADV_DONTNEED can miss the THP which can lead to userspace breakage.
See example of such race in commit message of patch 2/4.
All these races are found by code inspection. I haven't seen them triggered. I don't think it's worth to apply them to stable@.
This patch (of 4):
Restructure code in preparation for a fix.
Link: http://lkml.kernel.org/r/20170302151034.27829-2-kirill.shutemov@linux.intel.... Signed-off-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Acked-by: Vlastimil Babka vbabka@suse.cz Cc: Andrea Arcangeli aarcange@redhat.com Cc: Hillf Danton hillf.zj@alibaba-inc.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org [jwang: adjust context for 4.4 kernel] Signed-off-by: Jack Wang jinpu.wang@profitbricks.com --- mm/huge_memory.c | 50 ++++++++++++++++++++++++++------------------------ 1 file changed, 26 insertions(+), 24 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 8f3769e..ea013cb 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1566,35 +1566,37 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, { struct mm_struct *mm = vma->vm_mm; spinlock_t *ptl; + pmd_t entry; + bool preserve_write; + int ret = 0;
- if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { - pmd_t entry; - bool preserve_write = prot_numa && pmd_write(*pmd); - ret = 1; + if (__pmd_trans_huge_lock(pmd, vma, &ptl) != 1) + return 0;
- /* - * Avoid trapping faults against the zero page. The read-only - * data is likely to be read-cached on the local CPU and - * local/remote hits to the zero page are not interesting. - */ - if (prot_numa && is_huge_zero_pmd(*pmd)) { - spin_unlock(ptl); - return ret; - } + preserve_write = prot_numa && pmd_write(*pmd); + ret = 1;
- if (!prot_numa || !pmd_protnone(*pmd)) { - entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd); - entry = pmd_modify(entry, newprot); - if (preserve_write) - entry = pmd_mkwrite(entry); - ret = HPAGE_PMD_NR; - set_pmd_at(mm, addr, pmd, entry); - BUG_ON(!preserve_write && pmd_write(entry)); - } - spin_unlock(ptl); - } + /* + * Avoid trapping faults against the zero page. The read-only + * data is likely to be read-cached on the local CPU and + * local/remote hits to the zero page are not interesting. + */ + if (prot_numa && is_huge_zero_pmd(*pmd)) + goto unlock; + + if (prot_numa && pmd_protnone(*pmd)) + goto unlock;
+ entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd); + entry = pmd_modify(entry, newprot); + if (preserve_write) + entry = pmd_mkwrite(entry); + ret = HPAGE_PMD_NR; + set_pmd_at(mm, addr, pmd, entry); + BUG_ON(!preserve_write && pmd_write(entry)); +unlock: + spin_unlock(ptl); return ret; }
On Thu, Dec 07, 2017 at 11:22:50AM +0100, Jack Wang wrote:
From: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com
commit 0a85e51d37645e9ce57e5e1a30859e07810ed07c upstream.
Patch series "thp: fix few MADV_DONTNEED races"
For MADV_DONTNEED to work properly with huge pages, it's critical to not clear pmd intermittently unless you hold down_write(mmap_sem).
Otherwise MADV_DONTNEED can miss the THP which can lead to userspace breakage.
See example of such race in commit message of patch 2/4.
All these races are found by code inspection. I haven't seen them triggered. I don't think it's worth to apply them to stable@.
This patch (of 4):
What about all 4 of these?
And should this also go into 4.9? I don't want to include fixes into 4.4-stable without them also being in 4.9-stable, as that would be a regression for people upgrading.
thanks,
greg k-h
On Thu, Dec 7, 2017 at 1:05 PM, Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
On Thu, Dec 07, 2017 at 11:22:50AM +0100, Jack Wang wrote:
From: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com
commit 0a85e51d37645e9ce57e5e1a30859e07810ed07c upstream.
Patch series "thp: fix few MADV_DONTNEED races"
For MADV_DONTNEED to work properly with huge pages, it's critical to not clear pmd intermittently unless you hold down_write(mmap_sem).
Otherwise MADV_DONTNEED can miss the THP which can lead to userspace breakage.
See example of such race in commit message of patch 2/4.
All these races are found by code inspection. I haven't seen them triggered. I don't think it's worth to apply them to stable@.
This patch (of 4):
What about all 4 of these?
The 4 patches were from here: http://lkml.iu.edu/hypermail/linux/kernel/1703.0/01274.html
thp: reduce indentation level in change_huge_pmd() thp: fix MADV_DONTNEED vs. numa balancing race thp: fix MADV_DONTNEED vs. MADV_FREE race (the function exists only since 4.5+ ) thp: fix MADV_DONTNEED vs clear soft dirty race (this one already included since 4.4.63)
And should this also go into 4.9? I don't want to include fixes into 4.4-stable without them also being in 4.9-stable, as that would be a regression for people upgrading.
In 4.9, the last 2 were already applied, I will try to backport these 3 commits also to 4.9 stable.
thanks,
greg k-h
Thanks,
On Thu, Dec 07, 2017 at 01:25:19PM +0100, Jinpu Wang wrote:
On Thu, Dec 7, 2017 at 1:05 PM, Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
On Thu, Dec 07, 2017 at 11:22:50AM +0100, Jack Wang wrote:
From: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com
commit 0a85e51d37645e9ce57e5e1a30859e07810ed07c upstream.
Patch series "thp: fix few MADV_DONTNEED races"
For MADV_DONTNEED to work properly with huge pages, it's critical to not clear pmd intermittently unless you hold down_write(mmap_sem).
Otherwise MADV_DONTNEED can miss the THP which can lead to userspace breakage.
See example of such race in commit message of patch 2/4.
All these races are found by code inspection. I haven't seen them triggered. I don't think it's worth to apply them to stable@.
This patch (of 4):
What about all 4 of these?
The 4 patches were from here: http://lkml.iu.edu/hypermail/linux/kernel/1703.0/01274.html
thp: reduce indentation level in change_huge_pmd() thp: fix MADV_DONTNEED vs. numa balancing race thp: fix MADV_DONTNEED vs. MADV_FREE race (the function exists only since 4.5+ ) thp: fix MADV_DONTNEED vs clear soft dirty race (this one already included since 4.4.63)
And should this also go into 4.9? I don't want to include fixes into 4.4-stable without them also being in 4.9-stable, as that would be a regression for people upgrading.
In 4.9, the last 2 were already applied, I will try to backport these 3 commits also to 4.9 stable.
Thanks for all of these now, all queued up.
greg k-h
linux-stable-mirror@lists.linaro.org
-
Greg Kroah-Hartman -
Jack Wang -
Jinpu Wang