[lkml]   [2021]   [Nov]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH v2] hugetlb, userfaultfd: Fix reservation restore on userfaultfd error
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 <>


Fixes: c7b1850dfb41 ("hugetlb: don't pass page cache pages to restore_reserve_on_error")
Signed-off-by: Mina Almasry <>
Reported-by: James Houghton <>


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)
- if (!new_pagecache_page)
+ if (!page_in_pagecache)
restore_reserve_on_error(h, dst_vma, dst_addr, page);
goto out;
 \ /
  Last update: 2021-11-17 20:39    [W:0.051 / U:0.064 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site