iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

lkdtm/usercopy: Expand size of "out of frame" object

Browse Source 
[ Upstream commit f387e86d3a74407bdd9c5815820ac9d060962840 ]

To be sufficiently out of range for the usercopy test to see the lifetime
mismatch, expand the size of the "bad" buffer, which will let it be
beyond current_stack_pointer regardless of stack growth direction.
Paired with the recent addition of stack depth checking under
CONFIG_HARDENED_USERCOPY=y, this will correctly start tripping again.

Reported-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Link: https://lore.kernel.org/lkml/762faf1b-0443-5ddf-4430-44a20cf2ec4d@collabora.com/
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Kees Cook 2022-02-16 12:15:03 -08:00 committed by Greg Kroah-Hartman
parent 7821d743ab
commit 61ca1b97ad
1 changed files with 14 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
drivers/misc/lkdtm/usercopy.c
View File

@ -30,12 +30,12 @@ static const unsigned char test_text[] = "This is a test.\n";
*/
static noinline unsigned char *trick_compiler(unsigned char *stack)
{
return stack + 0;
return stack + unconst;
}
static noinline unsigned char *do_usercopy_stack_callee(int value)
{
unsigned char buf[32];
unsigned char buf[128];
int i;
/* Exercise stack to avoid everything living in registers. */
@ -43,7 +43,12 @@ static noinline unsigned char *do_usercopy_stack_callee(int value)
buf[i] = value & 0xff;
}
return trick_compiler(buf);
/*
* Put the target buffer in the middle of stack allocation
* so that we don't step on future stack users regardless
* of stack growth direction.
*/
return trick_compiler(&buf[(128/2)-32]);
}
static noinline void do_usercopy_stack(bool to_user, bool bad_frame)
@ -66,6 +71,12 @@ static noinline void do_usercopy_stack(bool to_user, bool bad_frame)
bad_stack -= sizeof(unsigned long);
}
#ifdef ARCH_HAS_CURRENT_STACK_POINTER
pr_info("stack : %px\n", (void *)current_stack_pointer);
#endif
pr_info("good_stack: %px-%px\n", good_stack, good_stack + sizeof(good_stack));
pr_info("bad_stack : %px-%px\n", bad_stack, bad_stack + sizeof(good_stack));
user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_ANONYMOUS | MAP_PRIVATE, 0);