This is a note to let you know that I've just added the patch titled
hugetlb, userfaultfd: fix reservation restore on userfaultfd error
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
hugetlb-userfaultfd-fix-reservation-restore-on-userfaultfd-error.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From cc30042df6fcc82ea18acf0dace831503e60a0b7 Mon Sep 17 00:00:00 2001
From: Mina Almasry <almasrymina@xxxxxxxxxx>
Date: Fri, 19 Nov 2021 16:43:43 -0800
Subject: hugetlb, userfaultfd: fix reservation restore on userfaultfd error
From: Mina Almasry <almasrymina@xxxxxxxxxx>
commit cc30042df6fcc82ea18acf0dace831503e60a0b7 upstream.
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.
Link: https://lkml.kernel.org/r/20211117193825.378528-1-almasrymina@xxxxxxxxxx
Fixes: c7b1850dfb41 ("hugetlb: don't pass page cache pages to restore_reserve_on_error")
Signed-off-by: Mina Almasry <almasrymina@xxxxxxxxxx>
Reported-by: James Houghton <jthoughton@xxxxxxxxxx>
Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Wei Xu <weixugc@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5236,13 +5236,14 @@ int hugetlb_mcopy_atomic_pte(struct mm_s
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.
@@ -5330,7 +5331,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_s
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);
@@ -5394,7 +5395,7 @@ out_release_unlock:
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;
Patches currently in stable-queue which might be from almasrymina@xxxxxxxxxx are
queue-5.15/hugetlb-userfaultfd-fix-reservation-restore-on-userfaultfd-error.patch
