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authorKees Cook <keescook@chromium.org>2022-02-16 23:15:03 +0300
committerKees Cook <keescook@chromium.org>2022-04-13 02:11:50 +0300
commitf387e86d3a74407bdd9c5815820ac9d060962840 (patch)
tree251f6d15a95c445aae3dde986114ade4781fff41 /drivers/misc/lkdtm
parent42db2594e4cd4a3c29aad87f80b1c00bf7751afe (diff)
downloadlinux-f387e86d3a74407bdd9c5815820ac9d060962840.tar.xz
lkdtm/usercopy: Expand size of "out of frame" object
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>
Diffstat (limited to 'drivers/misc/lkdtm')
-rw-r--r--drivers/misc/lkdtm/usercopy.c17
1 files changed, 14 insertions, 3 deletions
diff --git a/drivers/misc/lkdtm/usercopy.c b/drivers/misc/lkdtm/usercopy.c
index 9161ce7ed47a..3fead5efe523 100644
--- a/drivers/misc/lkdtm/usercopy.c
+++ b/drivers/misc/lkdtm/usercopy.c
@@ -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);