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lkdtm/usercopy: Moves the KERNEL_DS test to non-canonical 

The prior implementation of the KERNEL_DS fault checking would work on
any unmapped kernel address, but this was narrowed to the non-canonical
range instead. This adjusts the LKDTM test to match.

Fixes: 00c42373d3 ("x86-64: add warning for non-canonical user access address dereferences")
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook 2019-04-06 08:52:11 -07:00
parent 8c2ffd9174
commit 2bf8496f6e
1 changed files with 6 additions and 4 deletions
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10
drivers/misc/lkdtm/usercopy.c
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@ -324,14 +324,16 @@ free_user:
void lkdtm_USERCOPY_KERNEL_DS(void)
{
char __user *user_ptr = (char __user *)ERR_PTR(-EINVAL);
char __user *user_ptr =
(char __user *)(0xFUL << (sizeof(unsigned long) * 8 - 4));
mm_segment_t old_fs = get_fs();
char buf[10] = {0};
pr_info("attempting copy_to_user on unmapped kernel address\n");
pr_info("attempting copy_to_user() to noncanonical address: %px\n",
user_ptr);
set_fs(KERNEL_DS);
if (copy_to_user(user_ptr, buf, sizeof(buf)))
pr_info("copy_to_user un unmapped kernel address failed\n");
if (copy_to_user(user_ptr, buf, sizeof(buf)) == 0)
pr_err("copy_to_user() to noncanonical address succeeded!?\n");
set_fs(old_fs);
}