The patch titled
Subject: mm/gup.c: remove some BUG_ONs from get_gate_page()
has been added to the -mm tree. Its filename is
mm-gup-remove-some-bug_ons-from-get_gate_page.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-gup-remove-some-bug_ons-from-get_gate_page.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-gup-remove-some-bug_ons-from-get_gate_page.patch
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The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Andy Lutomirski <luto@xxxxxxxxxx>
Subject: mm/gup.c: remove some BUG_ONs from get_gate_page()
If we end up without a PGD or PUD entry backing the gate area, don't BUG
-- just fail gracefully.
It's not entirely implausible that this could happen some day on x86. It
doesn't right now even with an execute-only emulated vsyscall page because
the fixmap shares the PUD, but the core mm code shouldn't rely on that
particular detail to avoid OOPSing.
Link: http://lkml.kernel.org/r/a1d9f4efb75b9d464e59fd6af00104b21c58f6f7.1561610798.git.luto@xxxxxxxxxx
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Florian Weimer <fweimer@xxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/gup.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
--- a/mm/gup.c~mm-gup-remove-some-bug_ons-from-get_gate_page
+++ a/mm/gup.c
@@ -586,11 +586,14 @@ static int get_gate_page(struct mm_struc
pgd = pgd_offset_k(address);
else
pgd = pgd_offset_gate(mm, address);
- BUG_ON(pgd_none(*pgd));
+ if (pgd_none(*pgd))
+ return -EFAULT;
p4d = p4d_offset(pgd, address);
- BUG_ON(p4d_none(*p4d));
+ if (p4d_none(*p4d))
+ return -EFAULT;
pud = pud_offset(p4d, address);
- BUG_ON(pud_none(*pud));
+ if (pud_none(*pud))
+ return -EFAULT;
pmd = pmd_offset(pud, address);
if (!pmd_present(*pmd))
return -EFAULT;
_
Patches currently in -mm which might be from luto@xxxxxxxxxx are
mm-gup-remove-some-bug_ons-from-get_gate_page.patch
