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Message-Id: <20180807012257.20157-2-jannh@google.com>
Date: Tue, 7 Aug 2018 03:22:57 +0200
From: Jann Horn <jannh@...gle.com>
To: Kees Cook <keescook@...omium.org>, Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
kernel-hardening@...ts.openwall.com, jannh@...gle.com
Cc: linux-kernel@...r.kernel.org, Andy Lutomirski <luto@...nel.org>, dvyukov@...gle.com
Subject: [RFC PATCH 2/2] 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. Test with "DIRECT" mode.
Signed-off-by: Jann Horn <jannh@...gle.com>
---
drivers/misc/lkdtm/core.c | 1 +
drivers/misc/lkdtm/lkdtm.h | 1 +
drivers/misc/lkdtm/usercopy.c | 13 +++++++++++++
3 files changed, 15 insertions(+)
diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
index 2154d1bfd18b..5a755590d3dc 100644
--- 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 9e513dcfd809..07db641d71d0 100644
--- 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 9725aed305bb..389475b25bb7 100644
--- a/drivers/misc/lkdtm/usercopy.c
+++ b/drivers/misc/lkdtm/usercopy.c
@@ -322,6 +322,19 @@ void lkdtm_USERCOPY_KERNEL(void)
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. */
--
2.18.0.597.ga71716f1ad-goog
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