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authorAndy Lutomirski <luto@kernel.org>2019-07-11 20:57:43 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-07-12 11:05:45 -0700
commitb5d1c39f34d1c9bca0c4b9ae2e339fbbe264a9c7 (patch)
treea3f85255181b5ad7416dc978c3c74bc88e6088a1 /mm/gup.c
parentaa712399c1e8245c375a5c44760de684ec2ebefb (diff)
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@kernel.org Signed-off-by: Andy Lutomirski <luto@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Florian Weimer <fweimer@redhat.com> Cc: Jann Horn <jannh@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/gup.c')
-rw-r--r--mm/gup.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/mm/gup.c b/mm/gup.c
index f411bab037f5..bb4ad57d20e3 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -586,11 +586,14 @@ static int get_gate_page(struct mm_struct *mm, unsigned long address,
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;