On Mon, Jun 03, 2019 at 06:55:05PM +0200, Andrey Konovalov wrote:
This patch is a part of a series that extends arm64 kernel ABI to allow to pass tagged user pointers (with the top byte set to something else other than 0x00) as syscall arguments.
strncpy_from_user and strnlen_user accept user addresses as arguments, and do not go through the same path as copy_from_user and others, so here we need to handle the case of tagged user addresses separately.
Untag user pointers passed to these functions.
Note, that this patch only temporarily untags the pointers to perform validity checks, but then uses them as is to perform user memory accesses.
Reviewed-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Andrey Konovalov andreyknvl@google.com
Acked-by: Kees Cook keescook@chromium.org
-Kees
lib/strncpy_from_user.c | 3 ++- lib/strnlen_user.c | 3 ++- 2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c index 023ba9f3b99f..dccb95af6003 100644 --- a/lib/strncpy_from_user.c +++ b/lib/strncpy_from_user.c @@ -6,6 +6,7 @@ #include <linux/uaccess.h> #include <linux/kernel.h> #include <linux/errno.h> +#include <linux/mm.h> #include <asm/byteorder.h> #include <asm/word-at-a-time.h> @@ -108,7 +109,7 @@ long strncpy_from_user(char *dst, const char __user *src, long count) return 0; max_addr = user_addr_max();
- src_addr = (unsigned long)src;
- src_addr = (unsigned long)untagged_addr(src); if (likely(src_addr < max_addr)) { unsigned long max = max_addr - src_addr; long retval;
diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c index 7f2db3fe311f..28ff554a1be8 100644 --- a/lib/strnlen_user.c +++ b/lib/strnlen_user.c @@ -2,6 +2,7 @@ #include <linux/kernel.h> #include <linux/export.h> #include <linux/uaccess.h> +#include <linux/mm.h> #include <asm/word-at-a-time.h> @@ -109,7 +110,7 @@ long strnlen_user(const char __user *str, long count) return 0; max_addr = user_addr_max();
- src_addr = (unsigned long)str;
- src_addr = (unsigned long)untagged_addr(str); if (likely(src_addr < max_addr)) { unsigned long max = max_addr - src_addr; long retval;
-- 2.22.0.rc1.311.g5d7573a151-goog