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Message-Id: <20181127100044.GA16502@rapoport-lnx>
Date: Tue, 27 Nov 2018 12:00:45 +0200
From: Mike Rapoport <rppt@...ux.ibm.com>
To: Sasha Levin <sashal@...nel.org>
Cc: Andrea Arcangeli <aarcange@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 4/5] userfaultfd: shmem: add i_size checks
Hi,
On Tue, Nov 27, 2018 at 06:57:32AM +0000, Sasha Levin wrote:
> Hi,
>
> [This is an automated email]
>
> This commit has been processed because it contains a "Fixes:" tag,
> fixing commit: 4c27fe4c4c84 userfaultfd: shmem: add shmem_mcopy_atomic_pte for userfaultfd support.
>
> The bot has tested the following trees: v4.19.4, v4.14.83,
>
> v4.19.4: Build OK!
> v4.14.83: Failed to apply! Possible dependencies:
> 2a70f6a76bb8 ("memcg, thp: do not invoke oom killer on thp charges")
> 2cf855837b89 ("memcontrol: schedule throttling if we are congested")
>
>
> How should we proceed with this patch?
Below is the same patch backported to 4.14.83. With it the patch 5/5 in the
series applies cleanly.
>From 89135f0df0323f38c0b036c87688f5a7e3cfa9e9 Mon Sep 17 00:00:00 2001
From: Andrea Arcangeli <aarcange@...hat.com>
Date: Mon, 26 Nov 2018 12:34:51 -0500
Subject: [PATCH v4.14.83] userfaultfd: shmem: add i_size checks
With MAP_SHARED: recheck the i_size after taking the PT lock, to
serialize against truncate with the PT lock. Delete the page from the
pagecache if the i_size_read check fails.
With MAP_PRIVATE: check the i_size after the PT lock before mapping
anonymous memory or zeropages into the MAP_PRIVATE shmem mapping.
A mostly irrelevant cleanup: like we do the delete_from_page_cache()
pagecache removal after dropping the PT lock, the PT lock is a
spinlock so drop it before the sleepable page lock.
Reviewed-by: Mike Rapoport <rppt@...ux.ibm.com>
Reviewed-by: Hugh Dickins <hughd@...gle.com>
Reported-by: Jann Horn <jannh@...gle.com>
Fixes: 4c27fe4c4c84 ("userfaultfd: shmem: add shmem_mcopy_atomic_pte for userfaultfd support")
Cc: stable@...r.kernel.org
Signed-off-by: Andrea Arcangeli <aarcange@...hat.com>
Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
---
mm/shmem.c | 18 ++++++++++++++++--
mm/userfaultfd.c | 26 ++++++++++++++++++++++++--
2 files changed, 40 insertions(+), 4 deletions(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index 8019118..70b9fb9 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2238,6 +2238,7 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
struct page *page;
pte_t _dst_pte, *dst_pte;
int ret;
+ pgoff_t offset, max_off;
ret = -ENOMEM;
if (!shmem_inode_acct_block(inode, 1))
@@ -2275,6 +2276,12 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
__SetPageSwapBacked(page);
__SetPageUptodate(page);
+ ret = -EFAULT;
+ offset = linear_page_index(dst_vma, dst_addr);
+ max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+ if (unlikely(offset >= max_off))
+ goto out_release;
+
ret = mem_cgroup_try_charge(page, dst_mm, gfp, &memcg, false);
if (ret)
goto out_release;
@@ -2293,8 +2300,14 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
if (dst_vma->vm_flags & VM_WRITE)
_dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte));
- ret = -EEXIST;
dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
+
+ ret = -EFAULT;
+ max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+ if (unlikely(offset >= max_off))
+ goto out_release_uncharge_unlock;
+
+ ret = -EEXIST;
if (!pte_none(*dst_pte))
goto out_release_uncharge_unlock;
@@ -2312,13 +2325,14 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
/* No need to invalidate - it was non-present before */
update_mmu_cache(dst_vma, dst_addr, dst_pte);
- unlock_page(page);
pte_unmap_unlock(dst_pte, ptl);
+ unlock_page(page);
ret = 0;
out:
return ret;
out_release_uncharge_unlock:
pte_unmap_unlock(dst_pte, ptl);
+ delete_from_page_cache(page);
out_release_uncharge:
mem_cgroup_cancel_charge(page, memcg, false);
out_release:
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 5dbfcac0..5d70fdb 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -34,6 +34,8 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm,
void *page_kaddr;
int ret;
struct page *page;
+ pgoff_t offset, max_off;
+ struct inode *inode;
if (!*pagep) {
ret = -ENOMEM;
@@ -74,8 +76,17 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm,
if (dst_vma->vm_flags & VM_WRITE)
_dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte));
- ret = -EEXIST;
dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
+ if (dst_vma->vm_file) {
+ /* the shmem MAP_PRIVATE case requires checking the i_size */
+ inode = dst_vma->vm_file->f_inode;
+ offset = linear_page_index(dst_vma, dst_addr);
+ max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+ ret = -EFAULT;
+ if (unlikely(offset >= max_off))
+ goto out_release_uncharge_unlock;
+ }
+ ret = -EEXIST;
if (!pte_none(*dst_pte))
goto out_release_uncharge_unlock;
@@ -109,11 +120,22 @@ static int mfill_zeropage_pte(struct mm_struct *dst_mm,
pte_t _dst_pte, *dst_pte;
spinlock_t *ptl;
int ret;
+ pgoff_t offset, max_off;
+ struct inode *inode;
_dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
dst_vma->vm_page_prot));
- ret = -EEXIST;
dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
+ if (dst_vma->vm_file) {
+ /* the shmem MAP_PRIVATE case requires checking the i_size */
+ inode = dst_vma->vm_file->f_inode;
+ offset = linear_page_index(dst_vma, dst_addr);
+ max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+ ret = -EFAULT;
+ if (unlikely(offset >= max_off))
+ goto out_unlock;
+ }
+ ret = -EEXIST;
if (!pte_none(*dst_pte))
goto out_unlock;
set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
--
2.7.4
> --
> Thanks,
> Sasha
>
--
Sincerely yours,
Mike.
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