[patch 55/86] uaccess: disallow > INT_MAX copy sizes

Andrew Morton
2019-12-05T00:52:43Z

From: Kees Cook <keescook@chromium.org>
Subject: uaccess: disallow > INT_MAX copy sizes

As we've done with VFS, string operations, etc, reject usercopy sizes
larger than INT_MAX, which would be nice to have for catching bugs related
to size calculation overflows[1].

This adds 10 bytes to x86_64 defconfig text and 1980 bytes to the data
section:

text data bss dec hex filename
19691167 5134320 1646664 26472151 193eed7 vmlinux.before
19691177 5136300 1646664 26474141 193f69d vmlinux.after

[1] https://marc.info/?l=linux-s390&m=156631939010493&w=2

Link: http://lkml.kernel.org/r/201908251612.F9902D7A@keescook
Signed-off-by: Kees Cook <keescook@chromium.org>
Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

include/linux/thread_info.h | 2 ++
1 file changed, 2 insertions(+)

--- a/include/linux/thread_info.h~uaccess-disallow-int_max-copy-sizes
+++ a/include/linux/thread_info.h
@@ -147,6 +147,8 @@ check_copy_size(const void *addr, size_t
__bad_copy_to();
return false;
}
+ if (WARN_ON_ONCE(bytes > INT_MAX))
+ return false;
check_object_size(addr, bytes, is_source);
return true;
}
_