From 1771c6e1a567ea0ba2cccc0a4ffe68a1419fd8ef Mon Sep 17 00:00:00 2001 From: Andrey Ryabinin Date: Fri, 20 May 2016 16:59:31 -0700 Subject: x86/kasan: instrument user memory access API Exchange between user and kernel memory is coded in assembly language. Which means that such accesses won't be spotted by KASAN as a compiler instruments only C code. Add explicit KASAN checks to user memory access API to ensure that userspace writes to (or reads from) a valid kernel memory. Note: Unlike others strncpy_from_user() is written mostly in C and KASAN sees memory accesses in it. However, it makes sense to add explicit check for all @count bytes that *potentially* could be written to the kernel. [aryabinin@virtuozzo.com: move kasan check under the condition] Link: http://lkml.kernel.org/r/1462869209-21096-1-git-send-email-aryabinin@virtuozzo.com Link: http://lkml.kernel.org/r/1462538722-1574-4-git-send-email-aryabinin@virtuozzo.com Signed-off-by: Andrey Ryabinin Cc: Alexander Potapenko Cc: Dmitry Vyukov Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: Thomas Gleixner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/strncpy_from_user.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'lib') diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c index 33840324138c..33f655ef48cd 100644 --- a/lib/strncpy_from_user.c +++ b/lib/strncpy_from_user.c @@ -1,5 +1,6 @@ #include #include +#include #include #include #include @@ -109,6 +110,7 @@ long strncpy_from_user(char *dst, const char __user *src, long count) unsigned long max = max_addr - src_addr; long retval; + kasan_check_write(dst, count); user_access_begin(); retval = do_strncpy_from_user(dst, src, count, max); user_access_end(); -- cgit v1.2.3