[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20190729190806.462204986@linuxfoundation.org>
Date: Mon, 29 Jul 2019 21:22:30 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Andy Lutomirski <luto@...nel.org>,
Kees Cook <keescook@...omium.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Florian Weimer <fweimer@...hat.com>,
Jann Horn <jannh@...gle.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.2 154/215] mm/gup.c: remove some BUG_ONs from get_gate_page()
[ Upstream commit b5d1c39f34d1c9bca0c4b9ae2e339fbbe264a9c7 ]
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@...nel.org>
Reviewed-by: Kees Cook <keescook@...omium.org>
Reviewed-by: Andrew Morton <akpm@...ux-foundation.org>
Cc: Florian Weimer <fweimer@...hat.com>
Cc: Jann Horn <jannh@...gle.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
mm/gup.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c
index 22855ff0b448..d2c14fc4b5d4 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -585,11 +585,14 @@ 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;
--
2.20.1
Powered by blists - more mailing lists