Commit bef45902 authored by Jann Horn's avatar Jann Horn Committed by Thomas Gleixner
Browse files

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: default avatarJann Horn <jannh@google.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarKees 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
parent 9da3f2b7

drivers/misc/lkdtm/core.c

+1 −0
Original line number Original line Diff line number Diff line
@@ -183,6 +183,7 @@ static const struct crashtype crashtypes[] = { 
	CRASHTYPE(USERCOPY_STACK_FRAME_FROM),

	CRASHTYPE(USERCOPY_STACK_FRAME_FROM),

	CRASHTYPE(USERCOPY_STACK_BEYOND),

	CRASHTYPE(USERCOPY_STACK_BEYOND),

	CRASHTYPE(USERCOPY_KERNEL),

	CRASHTYPE(USERCOPY_KERNEL),

	CRASHTYPE(USERCOPY_KERNEL_DS),

};

};

drivers/misc/lkdtm/lkdtm.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -82,5 +82,6 @@ void lkdtm_USERCOPY_STACK_FRAME_TO(void); 
void lkdtm_USERCOPY_STACK_FRAME_FROM(void);

void lkdtm_USERCOPY_STACK_FRAME_FROM(void);

void lkdtm_USERCOPY_STACK_BEYOND(void);

void lkdtm_USERCOPY_STACK_BEYOND(void);

void lkdtm_USERCOPY_KERNEL(void);

void lkdtm_USERCOPY_KERNEL(void);

void lkdtm_USERCOPY_KERNEL_DS(void);





#endif
 
#endif

drivers/misc/lkdtm/usercopy.c

+13 −0
Original line number Original line Diff line number Diff line
@@ -322,6 +322,19 @@ free_user: 
	vm_munmap(user_addr, PAGE_SIZE);

	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)

void __init lkdtm_usercopy_init(void)

{

{

	/* Prepare cache that lacks SLAB_USERCOPY flag. */

	/* Prepare cache that lacks SLAB_USERCOPY flag. */

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