Linux-mm Archive on lore.kernel.org
 help / color / Atom feed
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
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


             reply index

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 ` 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

Linux-mm Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-mm/0 linux-mm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-mm linux-mm/ https://lore.kernel.org/linux-mm \
		linux-mm@kvack.org
	public-inbox-index linux-mm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kvack.linux-mm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git