The patch titled
Subject: mm/gup: memfd: stop leaking pinned pages in low memory conditions
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-gup-memfd-stop-leaking-pinned-pages-in-low-memory-conditions.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-gup-memfd-stop-leaking-pinned-pages-in-low-memory-conditions.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: John Hubbard <jhubbard@xxxxxxxxxx>
Subject: mm/gup: memfd: stop leaking pinned pages in low memory conditions
Date: Thu, 17 Oct 2024 18:17:11 -0700
If check_and_migrate_movable_pages() fails, typically with -ENOMEM, then
memfd_pin_folios() will leave pages pinned. Those are leaked forever,
and are visible to user space as a memory leak.
Fix this by unpinning the folios that try_grab_folio(FOLL_PIN) has
pinned, in such error cases.
Link: https://lkml.kernel.org/r/20241018011711.183642-3-jhubbard@xxxxxxxxxx
Fixes: 89c1905d9c14 ("mm/gup: introduce memfd_pin_folios() for pinning memfd folios")
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Dave Airlie <airlied@xxxxxxxxxx>
Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Dongwon Kim <dongwon.kim@xxxxxxxxx>
Cc: Junxiao Chang <junxiao.chang@xxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Shigeru Yoshida <syoshida@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/gup.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
--- a/mm/gup.c~mm-gup-memfd-stop-leaking-pinned-pages-in-low-memory-conditions
+++ a/mm/gup.c
@@ -3719,12 +3719,10 @@ long memfd_pin_folios(struct file *memfd
ret = check_and_migrate_movable_folios(nr_folios, folios);
} while (ret == -EAGAIN);
- memalloc_pin_restore(flags);
- return ret ? ret : nr_folios;
err:
memalloc_pin_restore(flags);
- unpin_folios(folios, nr_folios);
-
- return ret;
+ if (ret)
+ unpin_folios(folios, nr_folios);
+ return ret ? ret : nr_folios;
}
EXPORT_SYMBOL_GPL(memfd_pin_folios);
_
Patches currently in -mm which might be from jhubbard@xxxxxxxxxx are
mm-gup-stop-leaking-pinned-pages-in-low-memory-conditions.patch
mm-gup-memfd-stop-leaking-pinned-pages-in-low-memory-conditions.patch
kaslr-rename-physmem_end-and-physmem_end-to-direct_map_physmem_end.patch
