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hugetlb, userfaultfd: fix reservation restore on userfaultfd error

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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@google.com
Fixes: c7b1850dfb ("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>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Wei Xu <weixugc@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mina Almasry 2021-11-19 16:43:43 -08:00 committed by Linus Torvalds
parent afe041c2d0
commit cc30042df6
1 changed files with 4 additions and 3 deletions
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7
mm/hugetlb.c
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@ -5736,13 +5736,14 @@ 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.
@ -5830,7 +5831,7 @@ 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);
@ -5894,7 +5895,7 @@ 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;