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[v7] Documentation/checkpatch: Prefer stracpy/strscpy over strcpy/strlcpy/strncpy.

Message ID 20190728160608.3119-1-nitin.r.gote@intel.com
State New, archived
Headers show
Series [v7] Documentation/checkpatch: Prefer stracpy/strscpy over strcpy/strlcpy/strncpy. | expand

Commit Message

NitinGote July 28, 2019, 4:06 p.m. UTC
From: Nitin Gote <nitin.r.gote@intel.com>

Added check in checkpatch.pl to deprecate strcpy(), strlcpy() and
strncpy() in favor of stracpy() or strscpy().

Updated Documentation/process/deprecated.rst for stracpy() and strscpy().

Signed-off-by: Nitin Gote <nitin.r.gote@intel.com>
 Change log:
 - Favored both stracpy() or strscpy(), as stracpy() preferred when the
   destination is char array (rather than string pointer).

 - Used stracpy() instead of strscpy().

 - Change the subject line as per review comment.
 - v5 is Reviewed-by: Kees Cook <keescook@chromium.org>

 - Removed "c:func:" from deprecated.rst as per review comment.

 - Avoided use of $check in implementation.
 - Incorporated trivial comments.

 - 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(-)

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diff --git a/Documentation/process/deprecated.rst b/Documentation/process/deprecated.rst
index 49e0f64a3427..b4c82589d301 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() or strscpy().

 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() or strscpy(). 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() or strscpy().

 Variable Length Arrays (VLAs)
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 342c7c781ba5..0e14a1ae6502 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 or strscpy",
+	"strlcpy"		=> "stracpy or strscpy",
+	"strncpy"		=> "stracpy or strscpy - 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/ &&