From 6d13de1489b6bf539695f96d945de3860e6d5e17 Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@chromium.org>
Date: Wed, 4 Dec 2019 16:52:40 -0800
Subject: [PATCH] uaccess: disallow > INT_MAX copy sizes
Git-commit: 6d13de1489b6bf539695f96d945de3860e6d5e17
Patch-mainline: v5.5-rc1
References: git-fixes

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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

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

diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index 659a4400517b..e93e249a4e9b 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -147,6 +147,8 @@ check_copy_size(const void *addr, size_t bytes, bool is_source)
 			__bad_copy_to();
 		return false;
 	}
+	if (WARN_ON_ONCE(bytes > INT_MAX))
+		return false;
 	check_object_size(addr, bytes, is_source);
 	return true;
 }
-- 
2.16.4