Skip to content

Commit

Permalink
mm/debug_vm_pgtable: fix alignment for pmd/pud_advanced_tests()
Browse files Browse the repository at this point in the history
commit 04f7ce3 upstream.

In pmd/pud_advanced_tests(), the vaddr is aligned up to the next pmd/pud
entry, and so it does not match the given pmdp/pudp and (aligned down)
pfn any more.

For s390, this results in memory corruption, because the IDTE
instruction used e.g.  in xxx_get_and_clear() will take the vaddr for
some calculations, in combination with the given pmdp.  It will then end
up with a wrong table origin, ending on ...ff8, and some of those
wrongly set low-order bits will also select a wrong pagetable level for
the index addition.  IDTE could therefore invalidate (or 0x20) something
outside of the page tables, depending on the wrongly picked index, which
in turn depends on the random vaddr.

As result, we sometimes see "BUG task_struct (Not tainted): Padding
overwritten" on s390, where one 0x5a padding value got overwritten with
0x7a.

Fix this by aligning down, similar to how the pmd/pud_aligned pfns are
calculated.

Link: https://lkml.kernel.org/r/20210525130043.186290-2-gerald.schaefer@linux.ibm.com
Fixes: a5c3b9f ("mm/debug_vm_pgtable: add tests validating advanced arch page table helpers")
Signed-off-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: <stable@vger.kernel.org>	[5.9+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  • Loading branch information
gerald-schaefer authored and gregkh committed Jun 10, 2021
1 parent c8d5fae commit 5f2e1e8
Showing 1 changed file with 2 additions and 2 deletions.
4 changes: 2 additions & 2 deletions mm/debug_vm_pgtable.c
Expand Up @@ -163,7 +163,7 @@ static void __init pmd_advanced_tests(struct mm_struct *mm,

pr_debug("Validating PMD advanced\n");
/* Align the address wrt HPAGE_PMD_SIZE */
vaddr = (vaddr & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE;
vaddr &= HPAGE_PMD_MASK;

pgtable_trans_huge_deposit(mm, pmdp, pgtable);

Expand Down Expand Up @@ -285,7 +285,7 @@ static void __init pud_advanced_tests(struct mm_struct *mm,

pr_debug("Validating PUD advanced\n");
/* Align the address wrt HPAGE_PUD_SIZE */
vaddr = (vaddr & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE;
vaddr &= HPAGE_PUD_MASK;

set_pud_at(mm, vaddr, pudp, pud);
pudp_set_wrprotect(mm, vaddr, pudp);
Expand Down

0 comments on commit 5f2e1e8

Please sign in to comment.