From: Miaohe Lin <linmiaohe@xxxxxxxxxx> Subject: mm: gup: fix potential pgmap refcnt leak in __gup_device_huge() When failed to try_grab_page, put_dev_pagemap() is missed. So pgmap refcnt will leak in this case. Also we remove the check for pgmap against NULL as it's also checked inside the put_dev_pagemap(). [akpm@xxxxxxxxxxxxxxxxxxxx: simplify, cleanup] [akpm@xxxxxxxxxxxxxxxxxxxx: fix return value] Link: https://lkml.kernel.org/r/20210807093620.21347-5-linmiaohe@xxxxxxxxxx Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> Fixes: 3faa52c03f44 ("mm/gup: track FOLL_PIN pages") Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx> Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx> Cc: Jan Kara <jack@xxxxxxx> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/gup.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) --- a/mm/gup.c~mm-gup-fix-potential-pgmap-refcnt-leak-in-__gup_device_huge +++ a/mm/gup.c @@ -2240,6 +2240,7 @@ static int __gup_device_huge(unsigned lo { int nr_start = *nr; struct dev_pagemap *pgmap = NULL; + int ret = 1; do { struct page *page = pfn_to_page(pfn); @@ -2247,21 +2248,22 @@ static int __gup_device_huge(unsigned lo pgmap = get_dev_pagemap(pfn, pgmap); if (unlikely(!pgmap)) { undo_dev_pagemap(nr, nr_start, flags, pages); - return 0; + ret = 0; + break; } SetPageReferenced(page); pages[*nr] = page; if (unlikely(!try_grab_page(page, flags))) { undo_dev_pagemap(nr, nr_start, flags, pages); - return 0; + ret = 0; + break; } (*nr)++; pfn++; } while (addr += PAGE_SIZE, addr != end); - if (pgmap) - put_dev_pagemap(pgmap); - return 1; + put_dev_pagemap(pgmap); + return ret; } static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, _
