linux-kernel - [PATCH v2 0/2] FORTIFY_SOURCE: detect intra-object overflow in string functions

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Message-Id: <20200120045424.16147-1-dja@axtens.net>
Date:   Mon, 20 Jan 2020 15:54:22 +1100
From:   Daniel Axtens <dja@...ens.net>
To:     kernel-hardening@...ts.openwall.com, akpm@...ux-foundation.org,
        keescook@...omium.org
Cc:     linux-kernel@...r.kernel.org, Daniel Axtens <dja@...ens.net>
Subject: [PATCH v2 0/2] FORTIFY_SOURCE: detect intra-object overflow in string functions

When the fortify feature was first introduced in commit 6974f0c4555e
("include/linux/string.h: add the option of fortified string.h functions"),
Daniel Micay observed:

  * It should be possible to optionally use __builtin_object_size(x, 1) for
    some functions (C strings) to detect intra-object overflows (like
    glibc's _FORTIFY_SOURCE=2), but for now this takes the conservative
    approach to avoid likely compatibility issues.

This patch set:

 - converts a number of string functions to use __builtin_object_size(x, 1)

 - adds LKDTM tests for both types of fortified function.

This change passes an allyesconfig on powerpc and x86, and an x86 kernel
built with it survives running with syz-stress from syzkaller, so it seems
safe so far.

Daniel Axtens (2):
  string.h: detect intra-object overflow in fortified string functions
  lkdtm: tests for FORTIFY_SOURCE

 drivers/misc/lkdtm/bugs.c  | 51 ++++++++++++++++++++++++++++++++++++++
 drivers/misc/lkdtm/core.c  |  2 ++
 drivers/misc/lkdtm/lkdtm.h |  2 ++
 include/linux/string.h     | 27 ++++++++++++--------
 4 files changed, 71 insertions(+), 11 deletions(-)

-- 
2.20.1