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Message-Id: <1520400451-11475-2-git-send-email-me@tobin.cc>
Date: Wed, 7 Mar 2018 16:27:30 +1100
From: "Tobin C. Harding" <me@...in.cc>
To: Kernel Hardening <kernel-hardening@...ts.openwall.com>,
Tycho Andersen <tycho@...ho.ws>
Cc: "Tobin C. Harding" <me@...in.cc>,
Kees Cook <keescook@...omium.org>,
Oleg Drokin <oleg.drokin@...el.com>,
Andreas Dilger <andreas.dilger@...el.com>,
James Simmons <jsimmons@...radead.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH 1/2] vla: define new safe vla macros
We would like to get rid of VLAs all together but in the mean time we
can make their usage safer.
Define a macro to use for declaring a VLA. Macro includes requested
'size' and 'max' allowed. Macro allocates storage for an array
equivalent to
int array[min(size, max)];
We also define a macro to check whether maximum size was reached.
Signed-off-by: Tobin C. Harding <me@...in.cc>
---
include/linux/vla.h | 15 +++++++++++++++
1 file changed, 15 insertions(+)
create mode 100644 include/linux/vla.h
diff --git a/include/linux/vla.h b/include/linux/vla.h
new file mode 100644
index 000000000000..ca0510d5e416
--- /dev/null
+++ b/include/linux/vla.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_VLA_H
+#define _LINUX_VLA_H
+
+#define VLA_DEFAULT_MAX 256
+
+/* evaluates 'size' and 'max' twice */
+#define VLA_SAFE(type, vla, size, max) type vla[(size) < (max) ? (size) : (max)]
+
+#define VLA_WARN_OVERSIZE(vla, size) \
+do { \
+ WARN(sizeof(vla) < size, "vla maximum exceeded\n"); \
+} while (0)
+
+#endif /* _LINUX_VLA_H */
--
2.7.4
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