+ mm-gup-take-mmap_lock-in-get_dump_page.patch added to -mm tree

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



The patch titled
     Subject: mm/gup: take mmap_lock in get_dump_page()
has been added to the -mm tree.  Its filename is
     mm-gup-take-mmap_lock-in-get_dump_page.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-gup-take-mmap_lock-in-get_dump_page.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-gup-take-mmap_lock-in-get_dump_page.patch

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next and is updated
there every 3-4 working days

------------------------------------------------------
From: Jann Horn <jannh@xxxxxxxxxx>
Subject: 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.

Link: http://lkml.kernel.org/r/20200827114932.3572699-7-jannh@xxxxxxxxxx
Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
Acked-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: "Eric W . Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/gup.c |   16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

--- a/mm/gup.c~mm-gup-take-mmap_lock-in-get_dump_page
+++ a/mm/gup.c
@@ -1552,19 +1552,23 @@ finish_or_fault:
  * 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.
  *
- * 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
 struct page *get_dump_page(unsigned long addr)
 {
-	struct vm_area_struct *vma;
+	struct mm_struct *mm = current->mm;
 	struct page *page;
+	int locked = 1;
+	int ret;
 
-	if (__get_user_pages_locked(current->mm, addr, 1, &page, &vma, NULL,
-				    FOLL_FORCE | FOLL_DUMP | FOLL_GET) < 1)
+	if (mmap_read_lock_killable(mm))
 		return NULL;
-	flush_cache_page(vma, addr, page_to_pfn(page));
-	return page;
+	ret = __get_user_pages_locked(mm, addr, 1, &page, NULL, &locked,
+				      FOLL_FORCE | FOLL_DUMP | FOLL_GET);
+	if (locked)
+		mmap_read_unlock(mm);
+	return (ret == 1) ? page : NULL;
 }
 #endif /* CONFIG_ELF_CORE */
 
_

Patches currently in -mm which might be from jannh@xxxxxxxxxx are

binfmt_elf_fdpic-stop-using-dump_emit-on-user-pointers-on-mmu.patch
coredump-let-dump_emit-bail-out-on-short-writes.patch
coredump-refactor-page-range-dumping-into-common-helper.patch
coredump-rework-elf-elf_fdpic-vma_dump_size-into-common-helper.patch
binfmt_elf-binfmt_elf_fdpic-use-a-vma-list-snapshot.patch
mm-gup-take-mmap_lock-in-get_dump_page.patch
mm-remove-the-now-unnecessary-mmget_still_valid-hack.patch




[Index of Archives]     [Kernel Archive]     [IETF Annouce]     [DCCP]     [Netdev]     [Networking]     [Security]     [Bugtraq]     [Yosemite]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux SCSI]

  Powered by Linux