* [PATCH v2] hugetlb, userfaultfd: Fix reservation restore on userfaultfd error
@ 2021-11-17 19:38 Mina Almasry
2021-11-17 20:44 ` Mike Kravetz
0 siblings, 1 reply; 2+ messages in thread
From: Mina Almasry @ 2021-11-17 19:38 UTC (permalink / raw)
To: Mike Kravetz, Andrew Morton
Cc: Mina Almasry, Wei Xu, stable, James Houghton, linux-mm, linux-kernel
Currently in the is_continue case in hugetlb_mcopy_atomic_pte(), if we
bail out using "goto out_release_unlock;" in the cases where idx >=
size, or !huge_pte_none(), the code will detect that new_pagecache_page
== false, and so call restore_reserve_on_error().
In this case I see restore_reserve_on_error() delete the reservation,
and the following call to remove_inode_hugepages() will increment
h->resv_hugepages causing a 100% reproducible leak.
We should treat the is_continue case similar to adding a page into the
pagecache and set new_pagecache_page to true, to indicate that there is
no reservation to restore on the error path, and we need not call
restore_reserve_on_error(). Rename new_pagecache_page to
page_in_pagecache to make that clear.
Cc: Wei Xu <weixugc@google.com>
Cc: stable@vger.kernel.org
Fixes: c7b1850dfb41 ("hugetlb: don't pass page cache pages to restore_reserve_on_error")
Signed-off-by: Mina Almasry <almasrymina@google.com>
Reported-by: James Houghton <jthoughton@google.com>
---
Changes in v2:
- Renamed new_pagecache_page to page_in_pagecache
- Removed unnecessary comment after the name update.
- Cc: stable
---
mm/hugetlb.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index e09159c957e3..e7ebc4b355cf 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5734,13 +5734,14 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
int ret = -ENOMEM;
struct page *page;
int writable;
- bool new_pagecache_page = false;
+ bool page_in_pagecache = false;
if (is_continue) {
ret = -EFAULT;
page = find_lock_page(mapping, idx);
if (!page)
goto out;
+ page_in_pagecache = true;
} else if (!*pagep) {
/* If a page already exists, then it's UFFDIO_COPY for
* a non-missing case. Return -EEXIST.
@@ -5828,7 +5829,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
ret = huge_add_to_page_cache(page, mapping, idx);
if (ret)
goto out_release_nounlock;
- new_pagecache_page = true;
+ page_in_pagecache = true;
}
ptl = huge_pte_lockptr(h, dst_mm, dst_pte);
@@ -5892,7 +5893,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
if (vm_shared || is_continue)
unlock_page(page);
out_release_nounlock:
- if (!new_pagecache_page)
+ if (!page_in_pagecache)
restore_reserve_on_error(h, dst_vma, dst_addr, page);
put_page(page);
goto out;
--
2.34.0.rc2.393.gf8c9666880-goog
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v2] hugetlb, userfaultfd: Fix reservation restore on userfaultfd error
2021-11-17 19:38 [PATCH v2] hugetlb, userfaultfd: Fix reservation restore on userfaultfd error Mina Almasry
@ 2021-11-17 20:44 ` Mike Kravetz
0 siblings, 0 replies; 2+ messages in thread
From: Mike Kravetz @ 2021-11-17 20:44 UTC (permalink / raw)
To: Mina Almasry, Andrew Morton
Cc: Wei Xu, stable, James Houghton, linux-mm, linux-kernel
On 11/17/21 11:38, Mina Almasry wrote:
> Currently in the is_continue case in hugetlb_mcopy_atomic_pte(), if we
> bail out using "goto out_release_unlock;" in the cases where idx >=
> size, or !huge_pte_none(), the code will detect that new_pagecache_page
> == false, and so call restore_reserve_on_error().
> In this case I see restore_reserve_on_error() delete the reservation,
> and the following call to remove_inode_hugepages() will increment
> h->resv_hugepages causing a 100% reproducible leak.
>
> We should treat the is_continue case similar to adding a page into the
> pagecache and set new_pagecache_page to true, to indicate that there is
> no reservation to restore on the error path, and we need not call
> restore_reserve_on_error(). Rename new_pagecache_page to
> page_in_pagecache to make that clear.
>
> Cc: Wei Xu <weixugc@google.com>
>
> Cc: stable@vger.kernel.org
>
> Fixes: c7b1850dfb41 ("hugetlb: don't pass page cache pages to restore_reserve_on_error")
> Signed-off-by: Mina Almasry <almasrymina@google.com>
> Reported-by: James Houghton <jthoughton@google.com>
>
>
> ---
>
> Changes in v2:
> - Renamed new_pagecache_page to page_in_pagecache
> - Removed unnecessary comment after the name update.
> - Cc: stable
Thanks for making the changes!
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
--
Mike Kravetz
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