fs/proc/kcore.c: Add bounce buffer for ktext data
We hit hardened usercopy feature check for kernel text access by reading
kcore file:
usercopy: kernel memory exposure attempt detected from ffffffff8179a01f (<kernel text>) (4065 bytes)
kernel BUG at mm/usercopy.c:75!
Bypassing this check for kcore by adding bounce buffer for ktext data.
Reported-by: Steve Best <sbest@redhat.com>
Fixes: f5509cc18daa ("mm: Hardened usercopy")
Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index bd3ac9d..5c89a07 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -509,7 +509,12 @@
if (kern_addr_valid(start)) {
unsigned long n;
- n = copy_to_user(buffer, (char *)start, tsz);
+ /*
+ * Using bounce buffer to bypass the
+ * hardened user copy kernel text checks.
+ */
+ memcpy(buf, (char *) start, tsz);
+ n = copy_to_user(buffer, buf, tsz);
/*
* We cannot distinguish between fault on source
* and fault on destination. When this happens
