From: Andy Lutomirski <luto@kernel.org>
To: LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>
Cc: x86@kernel.org, Kees Cook <keescook@chromium.org>,
Florian Weimer <fweimer@redhat.com>, Jann Horn <jannh@google.com>,
Andy Lutomirski <luto@kernel.org>
Subject: [PATCH] mm/gup: Remove some BUG_ONs from get_gate_page()
Date: Wed, 26 Jun 2019 21:47:30 -0700 [thread overview]
Message-ID: <a1d9f4efb75b9d464e59fd6af00104b21c58f6f7.1561610798.git.luto@kernel.org> (raw)
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.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
mm/gup.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c
index ddde097cf9e4..9883b598fd6f 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;
--
2.21.0
next reply other threads:[~2019-06-27 4:47 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-27 4:47 Andy Lutomirski [this message]
2019-06-27 15:53 ` [PATCH] mm/gup: Remove some BUG_ONs from get_gate_page() Kees Cook
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=a1d9f4efb75b9d464e59fd6af00104b21c58f6f7.1561610798.git.luto@kernel.org \
--to=luto@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=fweimer@redhat.com \
--cc=jannh@google.com \
--cc=keescook@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).