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

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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
This commit is contained in:
Jann Horn 2018-08-28 22:14:21 +02:00 committed by Thomas Gleixner
parent 9da3f2b740
commit bef459026b
3 changed files with 15 additions and 0 deletions
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1
drivers/misc/lkdtm/core.c
View file

@ -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),
};

1
drivers/misc/lkdtm/lkdtm.h
View file

@ -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

13
drivers/misc/lkdtm/usercopy.c
View file

@ -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. */