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Date: Thu, 25 Jul 2019 16:52:19 +0530
From: NitinGote <nitin.r.gote@...el.com>
To: joe@...ches.com,
keescook@...omium.org
Cc: corbet@....net,
akpm@...ux-foundation.org,
apw@...onical.com,
linux-doc@...r.kernel.org,
kernel-hardening@...ts.openwall.com,
Nitin Gote <nitin.r.gote@...el.com>
Subject: [PATCH v6] Documentation/checkpatch: Prefer stracpy over strcpy/strlcpy/strncpy.
From: Nitin Gote <nitin.r.gote@...el.com>
Added check in checkpatch.pl to deprecate strcpy(), strlcpy() and
strncpy() in favor of stracpy().
Updated Documentation/process/deprecated.rst for stracpy().
Signed-off-by: Nitin Gote <nitin.r.gote@...el.com>
---
Change log:
v5->v6
- Used stracpy() instead of strscpy().
v4->v5
- Change the subject line as per review comment.
- v5 is Reviewed-by: Kees Cook <keescook@...omium.org>
v3->v4
- Removed "c:func:" from deprecated.rst as per review comment.
v2->v3
- Avoided use of $check in implementation.
- Incorporated trivial comments.
v1->v2
- For string related apis, created different %deprecated_string_api
and these will get emitted at CHECK Level using command line option
-f/--file to avoid bad patched from novice script users.
Documentation/process/deprecated.rst | 10 +++++-----
scripts/checkpatch.pl | 24 ++++++++++++++++++++++++
2 files changed, 29 insertions(+), 5 deletions(-)
diff --git a/Documentation/process/deprecated.rst b/Documentation/process/deprecated.rst
index 49e0f64a3427..709662c71a1a 100644
--- a/Documentation/process/deprecated.rst
+++ b/Documentation/process/deprecated.rst
@@ -84,7 +84,7 @@ buffer. This could result in linear overflows beyond the
end of the buffer, leading to all kinds of misbehaviors. While
`CONFIG_FORTIFY_SOURCE=y` and various compiler flags help reduce the
risk of using this function, there is no good reason to add new uses of
-this function. The safe replacement is :c:func:`strscpy`.
+this function. The safe replacement is stracpy().
strncpy() on NUL-terminated strings
-----------------------------------
@@ -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
+stracpy(). If, however, the destination buffer still needs NUL-padding,
+the safe replacement is stracpy_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
@@ -107,7 +107,7 @@ strlcpy()
:c:func:`strlcpy` reads the entire source buffer first, possibly exceeding
the given limit of bytes to copy. This is inefficient and can lead to
linear read overflows if a source string is not NUL-terminated. The
-safe replacement is :c:func:`strscpy`.
+safe replacement is stracpy().
Variable Length Arrays (VLAs)
-----------------------------
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 342c7c781ba5..dddf5adf1aac 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -605,6 +605,20 @@ foreach my $entry (keys %deprecated_apis) {
}
$deprecated_apis_search = "(?:${deprecated_apis_search})";
+our %deprecated_string_apis = (
+ "strcpy" => "stracpy",
+ "strlcpy" => "stracpy",
+ "strncpy" => "stracpy - for non-NUL-terminated uses, strncpy dest should be __nonstring",
+);
+
+#Create a search pattern for all these strings apis to speed up a loop below
+our $deprecated_string_apis_search = "";
+foreach my $entry (keys %deprecated_string_apis) {
+ $deprecated_string_apis_search .= '|' if ($deprecated_string_apis_search ne "");
+ $deprecated_string_apis_search .= $entry;
+}
+$deprecated_string_apis_search = "(?:${deprecated_string_apis_search})";
+
our $mode_perms_world_writable = qr{
S_IWUGO |
S_IWOTH |
@@ -6446,6 +6460,16 @@ sub process {
"Deprecated use of '$deprecated_api', prefer '$new_api' instead\n" . $herecurr);
}
+# check for string deprecated apis
+ if ($line =~ /\b($deprecated_string_apis_search)\b\s*\(/) {
+ my $deprecated_string_api = $1;
+ my $new_api = $deprecated_string_apis{$deprecated_string_api};
+ my $msg_level = \&WARN;
+ $msg_level = \&CHK if ($file);
+ &{$msg_level}("DEPRECATED_API",
+ "Deprecated use of '$deprecated_string_api', prefer '$new_api' instead\n" . $herecurr);
+ }
+
# check for various structs that are normally const (ops, kgdb, device_tree)
# and avoid what seem like struct definitions 'struct foo {'
if ($line !~ /\bconst\b/ &&
--
2.17.1
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