linux-kernel - [stable backport PATCH] usercopy: Adjust tests to deal with SMAP/PAN

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20170526204040.1953914-1-arnd@arndb.de>
Date:   Fri, 26 May 2017 22:40:33 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     stable@...r.kernel.org, Kees Cook <keescook@...omium.org>,
        Arnd Bergmann <arnd@...db.de>
Cc:     linux-arm-kernel@...ts.infradead.org, mark.rutland@....com,
        gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org
Subject: [stable backport PATCH] usercopy: Adjust tests to deal with SMAP/PAN

From: Kees Cook <keescook@...omium.org>

Commit f5f893c57e37ca730808cb2eee3820abd05e7507 upstream.

Under SMAP/PAN/etc, we cannot write directly to userspace memory, so
this rearranges the test bytes to get written through copy_to_user().
Additionally drops the bad copy_from_user() test that would trigger a
memcpy() against userspace on failure.

[arnd: the test module was added in 3.14, and this backported patch
       should apply cleanly on all version from 3.14 to 4.10.
       The original patch was in 4.11 on top of a context change.
       I saw the bug triggered with kselftest on a 4.4.y stable kernel]

Signed-off-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 lib/test_user_copy.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/lib/test_user_copy.c b/lib/test_user_copy.c
index 0ecef3e4690e..b16891d01112 100644
--- a/lib/test_user_copy.c
+++ b/lib/test_user_copy.c
@@ -58,7 +58,9 @@ static int __init test_user_copy_init(void)
 	usermem = (char __user *)user_addr;
 	bad_usermem = (char *)user_addr;
 
-	/* Legitimate usage: none of these should fail. */
+	/*
+	 * Legitimate usage: none of these copies should fail.
+	 */
 	ret |= test(copy_from_user(kmem, usermem, PAGE_SIZE),
 		    "legitimate copy_from_user failed");
 	ret |= test(copy_to_user(usermem, kmem, PAGE_SIZE),
@@ -68,19 +70,34 @@ static int __init test_user_copy_init(void)
 	ret |= test(put_user(value, (unsigned long __user *)usermem),
 		    "legitimate put_user failed");
 
-	/* Invalid usage: none of these should succeed. */
+	/*
+	 * Invalid usage: none of these copies should succeed.
+	 */
+
+	/* Reject kernel-to-kernel copies through copy_from_user(). */
 	ret |= test(!copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),
 				    PAGE_SIZE),
 		    "illegal all-kernel copy_from_user passed");
+
+#if 0
+	/*
+	 * When running with SMAP/PAN/etc, this will Oops the kernel
+	 * due to the zeroing of userspace memory on failure. This needs
+	 * to be tested in LKDTM instead, since this test module does not
+	 * expect to explode.
+	 */
 	ret |= test(!copy_from_user(bad_usermem, (char __user *)kmem,
 				    PAGE_SIZE),
 		    "illegal reversed copy_from_user passed");
+#endif
 	ret |= test(!copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,
 				  PAGE_SIZE),
 		    "illegal all-kernel copy_to_user passed");
 	ret |= test(!copy_to_user((char __user *)kmem, bad_usermem,
 				  PAGE_SIZE),
 		    "illegal reversed copy_to_user passed");
+
+	value = 0x5a;
 	ret |= test(!get_user(value, (unsigned long __user *)kmem),
 		    "illegal get_user passed");
 	ret |= test(!put_user(value, (unsigned long __user *)kmem),
-- 
2.9.0