lkdtm: Test copy_to_user() on bad kernel pointer under KERNEL_DS

Test whether the kernel WARN()s when, under KERNEL_DS, a bad kernel pointer
is used as "userspace" pointer. Should normally be used in "DIRECT" mode.

Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Kees Cook <keescook@chromium.org>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: kernel-hardening@lists.openwall.com
Cc: dvyukov@google.com
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Cc: Borislav Petkov <bp@alien8.de>
Link: https://lkml.kernel.org/r/20180828201421.157735-8-jannh@google.com

diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
index 2154d1bfd18b610b60f0fc8409cf7bf8919f2aad..5a755590d3dcefe85b0354c88bacc9dffd2e392d 100644 (file)
--- a/drivers/misc/lkdtm/core.c
+++ b/drivers/misc/lkdtm/core.c
@@ -183,6 +183,7 @@ static const struct crashtype crashtypes[] = {
        CRASHTYPE(USERCOPY_STACK_FRAME_FROM),
        CRASHTYPE(USERCOPY_STACK_BEYOND),
        CRASHTYPE(USERCOPY_KERNEL),
+       CRASHTYPE(USERCOPY_KERNEL_DS),
 };
 
 

diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
index 9e513dcfd8093613dd767765829158aa3addc810..07db641d71d023bd2eb710873114261170cce079 100644 (file)
--- a/drivers/misc/lkdtm/lkdtm.h
+++ b/drivers/misc/lkdtm/lkdtm.h
@@ -82,5 +82,6 @@ void lkdtm_USERCOPY_STACK_FRAME_TO(void);
 void lkdtm_USERCOPY_STACK_FRAME_FROM(void);
 void lkdtm_USERCOPY_STACK_BEYOND(void);
 void lkdtm_USERCOPY_KERNEL(void);
+void lkdtm_USERCOPY_KERNEL_DS(void);
 
 #endif

diff --git a/drivers/misc/lkdtm/usercopy.c b/drivers/misc/lkdtm/usercopy.c
index 9725aed305bbadad773c260dee8139f49fc093ca..389475b25bb7b61a3509a7db60e37543a2288c1d 100644 (file)
--- a/drivers/misc/lkdtm/usercopy.c
+++ b/drivers/misc/lkdtm/usercopy.c
@@ -322,6 +322,19 @@ free_user:
        vm_munmap(user_addr, PAGE_SIZE);
 }
 
+void lkdtm_USERCOPY_KERNEL_DS(void)
+{
+       char __user *user_ptr = (char __user *)ERR_PTR(-EINVAL);
+       mm_segment_t old_fs = get_fs();
+       char buf[10] = {0};
+
+       pr_info("attempting copy_to_user on unmapped kernel address\n");
+       set_fs(KERNEL_DS);
+       if (copy_to_user(user_ptr, buf, sizeof(buf)))
+               pr_info("copy_to_user un unmapped kernel address failed\n");
+       set_fs(old_fs);
+}
+
 void __init lkdtm_usercopy_init(void)
 {
        /* Prepare cache that lacks SLAB_USERCOPY flag. */