linux-kernel - [PATCH] checkpatch: Added warnings in favor of strscpy().

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Message-Id: <1562219683-15474-1-git-send-email-nitin.r.gote@intel.com>
Date:   Thu,  4 Jul 2019 11:24:43 +0530
From:   Nitin Gote <nitin.r.gote@...el.com>
To:     akpm@...ux-foundation.org
Cc:     corbet@....net, apw@...onical.com, joe@...ches.com,
        keescook@...omium.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com,
        Nitin Gote <nitin.r.gote@...el.com>
Subject: [PATCH] checkpatch: Added warnings in favor of strscpy().

Added warnings in checkpatch.pl script to :

1. Deprecate strcpy() in favor of strscpy().
2. Deprecate strlcpy() in favor of strscpy().
3. Deprecate strncpy() in favor of strscpy() or strscpy_pad().

Updated strncpy() section in Documentation/process/deprecated.rst
to cover strscpy_pad() case.

Signed-off-by: Nitin Gote <nitin.r.gote@...el.com>
---
 This patch is already reviewed by mailing list
 kernel-hardening@...ts.openwall.com. Refer below link
 <https://www.openwall.com/lists/kernel-hardening/2019/07/03/4>
Acked-by: Kees Cook <keescook@...omium.org>

 Documentation/process/deprecated.rst | 6 +++---
 scripts/checkpatch.pl                | 5 +++++
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/Documentation/process/deprecated.rst b/Documentation/process/deprecated.rst
index 49e0f64..f564de3 100644
--- a/Documentation/process/deprecated.rst
+++ b/Documentation/process/deprecated.rst
@@ -93,9 +93,9 @@ will be NUL terminated. This can lead to various linear read overflows
 and other misbehavior due to the missing termination. It also NUL-pads the
 destination buffer if the source contents are shorter than the destination
 buffer size, which may be a needless performance penalty for callers using
-only NUL-terminated strings. The safe replacement is :c:func:`strscpy`.
-(Users of :c:func:`strscpy` still needing NUL-padding will need an
-explicit :c:func:`memset` added.)
+only NUL-terminated strings. In this case, the safe replacement is
+:c:func:`strscpy`. If, however, the destination buffer still needs
+NUL-padding, the safe replacement is :c:func:`strscpy_pad`.
 
 If a caller is using non-NUL-terminated strings, :c:func:`strncpy()` can
 still be used, but destinations should be marked with the `__nonstring
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 342c7c7..3d80967 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -595,6 +595,11 @@ our %deprecated_apis = (
 	"rcu_barrier_sched"			=> "rcu_barrier",
 	"get_state_synchronize_sched"		=> "get_state_synchronize_rcu",
 	"cond_synchronize_sched"		=> "cond_synchronize_rcu",
+	"strcpy"				=> "strscpy",
+	"strlcpy"				=> "strscpy",
+	"strncpy"				=> "strscpy, strscpy_pad or for
+	non-NUL-terminated strings, strncpy() can still be used, but
+	destinations should be marked with the __nonstring",
 );
 
 #Create a search pattern for all these strings to speed up a loop below
-- 
2.7.4