Commit 7f3bfab5 authored by Jann Horn's avatar Jann Horn Committed by Linus Torvalds

mm/gup: take mmap_lock in get_dump_page()

Properly take the mmap_lock before calling into the GUP code from
get_dump_page(); and play nice, allowing the GUP code to drop the
mmap_lock if it has to sleep.

As Linus pointed out, we don't actually need the VMA because
__get_user_pages() will flush the dcache for us if necessary.
Signed-off-by: default avatarJann Horn <jannh@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Acked-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Eric W . Biederman" <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Link: http://lkml.kernel.org/r/20200827114932.3572699-7-jannh@google.comSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a07279c9
...@@ -1547,19 +1547,23 @@ static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start, ...@@ -1547,19 +1547,23 @@ static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start,
* NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found - * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
* allowing a hole to be left in the corefile to save diskspace. * allowing a hole to be left in the corefile to save diskspace.
* *
* Called without mmap_lock, but after all other threads have been killed. * Called without mmap_lock (takes and releases the mmap_lock by itself).
*/ */
#ifdef CONFIG_ELF_CORE #ifdef CONFIG_ELF_CORE
struct page *get_dump_page(unsigned long addr) struct page *get_dump_page(unsigned long addr)
{ {
struct vm_area_struct *vma; struct mm_struct *mm = current->mm;
struct page *page; struct page *page;
int locked = 1;
int ret;
if (__get_user_pages_locked(current->mm, addr, 1, &page, &vma, NULL, if (mmap_read_lock_killable(mm))
FOLL_FORCE | FOLL_DUMP | FOLL_GET) < 1)
return NULL; return NULL;
flush_cache_page(vma, addr, page_to_pfn(page)); ret = __get_user_pages_locked(mm, addr, 1, &page, NULL, &locked,
return page; FOLL_FORCE | FOLL_DUMP | FOLL_GET);
if (locked)
mmap_read_unlock(mm);
return (ret == 1) ? page : NULL;
} }
#endif /* CONFIG_ELF_CORE */ #endif /* CONFIG_ELF_CORE */
......
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