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UPSTREAM: fs/proc/kcore.c: Add bounce buffer for ktext data

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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>

Bug: 31374226
Change-Id: Ic93e6041b67d804a994518bf4950811f828b406e
(cherry picked from commit df04abfd181acc276ba6762c8206891ae10ae00d)
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
This commit is contained in:
Jiri Olsa 2016-09-08 09:57:08 +02:00 • committed by Amit Pundir
parent ac8c3e0150
commit 816619eef3
1 changed files with 6 additions and 1 deletions
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7
fs/proc/kcore.c
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@ -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