From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.7 required=3.0 tests=DATE_IN_FUTURE_06_12, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8771CCA90AF for ; Tue, 12 May 2020 18:01:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4381B20673 for ; Tue, 12 May 2020 18:01:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730628AbgELSBg (ORCPT ); Tue, 12 May 2020 14:01:36 -0400 Received: from ex13-edg-ou-002.vmware.com ([208.91.0.190]:56132 "EHLO EX13-EDG-OU-002.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725938AbgELSBg (ORCPT ); Tue, 12 May 2020 14:01:36 -0400 Received: from sc9-mailhost3.vmware.com (10.113.161.73) by EX13-EDG-OU-002.vmware.com (10.113.208.156) with Microsoft SMTP Server id 15.0.1156.6; Tue, 12 May 2020 11:00:53 -0700 Received: from localhost.localdomain (ashwinh-vm-1.vmware.com [10.110.19.225]) by sc9-mailhost3.vmware.com (Postfix) with ESMTP id 9B7624051F; Tue, 12 May 2020 11:00:52 -0700 (PDT) From: ashwin-h To: , , CC: , , , , , , , Linus Torvalds , Ashwin H Subject: [PATCH v4.19.x] make 'user_access_begin()' do 'access_ok()' Date: Wed, 13 May 2020 07:19:21 +0530 Message-ID: X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 Content-Type: text/plain Received-SPF: None (EX13-EDG-OU-002.vmware.com: ashwinh@vmware.com does not designate permitted sender hosts) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Linus Torvalds commit 594cc251fdd0d231d342d88b2fdff4bc42fb0690 upstream. Originally, the rule used to be that you'd have to do access_ok() separately, and then user_access_begin() before actually doing the direct (optimized) user access. But experience has shown that people then decide not to do access_ok() at all, and instead rely on it being implied by other operations or similar. Which makes it very hard to verify that the access has actually been range-checked. If you use the unsafe direct user accesses, hardware features (either SMAP - Supervisor Mode Access Protection - on x86, or PAN - Privileged Access Never - on ARM) do force you to use user_access_begin(). But nothing really forces the range check. By putting the range check into user_access_begin(), we actually force people to do the right thing (tm), and the range check vill be visible near the actual accesses. We have way too long a history of people trying to avoid them. Signed-off-by: Linus Torvalds Signed-off-by: Ashwin H --- arch/x86/include/asm/uaccess.h | 11 ++++++++++- drivers/gpu/drm/i915/i915_gem_execbuffer.c | 15 +++++++++++++-- include/linux/uaccess.h | 2 +- kernel/compat.c | 6 ++---- kernel/exit.c | 6 ++---- lib/strncpy_from_user.c | 9 +++++---- lib/strnlen_user.c | 9 +++++---- 7 files changed, 38 insertions(+), 20 deletions(-) diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 9718303..82cd874 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -711,7 +711,16 @@ extern struct movsl_mask { * checking before using them, but you have to surround them with the * user_access_begin/end() pair. */ -#define user_access_begin() __uaccess_begin() +static __must_check inline bool user_access_begin(const bool type, + const void __user *ptr, + size_t len) +{ + if (unlikely(!access_ok(type, ptr, len))) + return 0; + __uaccess_begin(); + return 1; +} +#define user_access_begin(t, a, b) user_access_begin(t, a, b) #define user_access_end() __uaccess_end() #define unsafe_put_user(x, ptr, err_label) \ diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c index f08c547..7110e8f 100644 --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c @@ -1604,7 +1604,9 @@ static int eb_copy_relocations(const struct i915_execbuffer *eb) * happened we would make the mistake of assuming that the * relocations were valid. */ - user_access_begin(); + if (!user_access_begin(VERIFY_WRITE, urelocs, size)) + goto end_user; + for (copied = 0; copied < nreloc; copied++) unsafe_put_user(-1, &urelocs[copied].presumed_offset, @@ -2649,7 +2651,16 @@ i915_gem_execbuffer2_ioctl(struct drm_device *dev, void *data, unsigned int i; /* Copy the new buffer offsets back to the user's exec list. */ - user_access_begin(); + /* + * Note: count * sizeof(*user_exec_list) does not overflow, + * because we checked 'count' in check_buffer_count(). + * + * And this range already got effectively checked earlier + * when we did the "copy_from_user()" above. + */ + if (!user_access_begin(VERIFY_WRITE, user_exec_list, count * sizeof(*user_exec_list))) + goto end_user; + for (i = 0; i < args->buffer_count; i++) { if (!(exec2_list[i].offset & UPDATE)) continue; diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h index efe79c1..d55b68b 100644 --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h @@ -267,7 +267,7 @@ extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count); probe_kernel_read(&retval, addr, sizeof(retval)) #ifndef user_access_begin -#define user_access_begin() do { } while (0) +#define user_access_begin(type, ptr, len) access_ok(type, ptr, len) #define user_access_end() do { } while (0) #define unsafe_get_user(x, ptr, err) do { if (unlikely(__get_user(x, ptr))) goto err; } while (0) #define unsafe_put_user(x, ptr, err) do { if (unlikely(__put_user(x, ptr))) goto err; } while (0) diff --git a/kernel/compat.c b/kernel/compat.c index 8e40efc..e4548a9 100644 --- a/kernel/compat.c +++ b/kernel/compat.c @@ -354,10 +354,9 @@ long compat_get_bitmap(unsigned long *mask, const compat_ulong_t __user *umask, bitmap_size = ALIGN(bitmap_size, BITS_PER_COMPAT_LONG); nr_compat_longs = BITS_TO_COMPAT_LONGS(bitmap_size); - if (!access_ok(VERIFY_READ, umask, bitmap_size / 8)) + if (!user_access_begin(VERIFY_READ, umask, bitmap_size / 8)) return -EFAULT; - user_access_begin(); while (nr_compat_longs > 1) { compat_ulong_t l1, l2; unsafe_get_user(l1, umask++, Efault); @@ -384,10 +383,9 @@ long compat_put_bitmap(compat_ulong_t __user *umask, unsigned long *mask, bitmap_size = ALIGN(bitmap_size, BITS_PER_COMPAT_LONG); nr_compat_longs = BITS_TO_COMPAT_LONGS(bitmap_size); - if (!access_ok(VERIFY_WRITE, umask, bitmap_size / 8)) + if (!user_access_begin(VERIFY_WRITE, umask, bitmap_size / 8)) return -EFAULT; - user_access_begin(); while (nr_compat_longs > 1) { unsigned long m = *mask++; unsafe_put_user((compat_ulong_t)m, umask++, Efault); diff --git a/kernel/exit.c b/kernel/exit.c index 54c3269..894fca5 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -1617,10 +1617,9 @@ SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *, if (!infop) return err; - if (!access_ok(VERIFY_WRITE, infop, sizeof(*infop))) + if (!user_access_begin(VERIFY_WRITE, infop, sizeof(*infop))) return -EFAULT; - user_access_begin(); unsafe_put_user(signo, &infop->si_signo, Efault); unsafe_put_user(0, &infop->si_errno, Efault); unsafe_put_user(info.cause, &infop->si_code, Efault); @@ -1745,10 +1744,9 @@ COMPAT_SYSCALL_DEFINE5(waitid, if (!infop) return err; - if (!access_ok(VERIFY_WRITE, infop, sizeof(*infop))) + if (!user_access_begin(VERIFY_WRITE, infop, sizeof(*infop))) return -EFAULT; - user_access_begin(); unsafe_put_user(signo, &infop->si_signo, Efault); unsafe_put_user(0, &infop->si_errno, Efault); unsafe_put_user(info.cause, &infop->si_code, Efault); diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c index e304b54..b8570a1 100644 --- a/lib/strncpy_from_user.c +++ b/lib/strncpy_from_user.c @@ -115,10 +115,11 @@ long strncpy_from_user(char *dst, const char __user *src, long count) kasan_check_write(dst, count); check_object_size(dst, count, false); - user_access_begin(); - retval = do_strncpy_from_user(dst, src, count, max); - user_access_end(); - return retval; + if (user_access_begin(VERIFY_READ, src, max)) { + retval = do_strncpy_from_user(dst, src, count, max); + user_access_end(); + return retval; + } } return -EFAULT; } diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c index 184f80f..f5fa5b2 100644 --- a/lib/strnlen_user.c +++ b/lib/strnlen_user.c @@ -114,10 +114,11 @@ long strnlen_user(const char __user *str, long count) unsigned long max = max_addr - src_addr; long retval; - user_access_begin(); - retval = do_strnlen_user(str, count, max); - user_access_end(); - return retval; + if (user_access_begin(VERIFY_READ, str, max)) { + retval = do_strnlen_user(str, count, max); + user_access_end(); + return retval; + } } return 0; } -- 2.7.4