The patch titled
Subject: lib/test_vmalloc.c: avoid garbage in page array
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
lib-test_vmallocc-avoid-garbage-in-page-array.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/lib-test_vmallocc-avoid-garbage-in-page-array.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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 via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Subject: lib/test_vmalloc.c: avoid garbage in page array
Date: Wed, 24 May 2023 09:24:24 +0100
It turns out that alloc_pages_bulk_array() does not treat the page_array
parameter as an output parameter, but rather reads the array and skips any
entries that have already been allocated.
This is somewhat unexpected and breaks this test, as we allocate the pages
array uninitialised on the assumption it will be overwritten.
As a result, the test was referencing uninitialised data and causing the
PFN to not be valid and thus a WARN_ON() followed by a null pointer deref
and panic.
In addition, this is an array of pointers not of struct page objects, so we
need only allocate an array with elements of pointer size.
We solve both problems by simply using kcalloc() and referencing
sizeof(struct page *) rather than sizeof(struct page).
Link: https://lkml.kernel.org/r/20230524082424.10022-1-lstoakes@xxxxxxxxx
Fixes: 869cb29a61a1 ("lib/test_vmalloc.c: add vm_map_ram()/vm_unmap_ram() test case")
Signed-off-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Cc: Baoquan He <bhe@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/test_vmalloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/lib/test_vmalloc.c~lib-test_vmallocc-avoid-garbage-in-page-array
+++ a/lib/test_vmalloc.c
@@ -369,7 +369,7 @@ vm_map_ram_test(void)
int i;
map_nr_pages = nr_pages > 0 ? nr_pages:1;
- pages = kmalloc(map_nr_pages * sizeof(struct page), GFP_KERNEL);
+ pages = kcalloc(map_nr_pages, sizeof(struct page *), GFP_KERNEL);
if (!pages)
return -1;
_
Patches currently in -mm which might be from lstoakes@xxxxxxxxx are
lib-test_vmallocc-avoid-garbage-in-page-array.patch
mm-mmap-separate-writenotify-and-dirty-tracking-logic.patch
mm-gup-disallow-foll_longterm-gup-nonfast-writing-to-file-backed-mappings.patch
mm-gup-disallow-foll_longterm-gup-fast-writing-to-file-backed-mappings.patch
mm-gup-add-missing-gup_must_unshare-check-to-gup_huge_pgd.patch
mm-gup-remove-unused-vmas-parameter-from-get_user_pages.patch
mm-gup-remove-unused-vmas-parameter-from-pin_user_pages_remote.patch
mm-gup-remove-vmas-parameter-from-get_user_pages_remote.patch
io_uring-rsrc-delegate-vma-file-backed-check-to-gup.patch
mm-gup-remove-vmas-parameter-from-pin_user_pages.patch
mm-gup-remove-vmas-array-from-internal-gup-functions.patch
mm-mmap-refactor-mlock_future_check.patch
