From df04abfd181acc276ba6762c8206891ae10ae00d Mon Sep 17 00:00:00 2001
From: Jiri Olsa <jolsa@kernel.org>
Date: Thu, 8 Sep 2016 09:57:08 +0200
Subject: 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>
---
fs/proc/kcore.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
(limited to 'fs')
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 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
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
--
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