[PATCH v3] checkpatch: Check for 0-length and 1-element arrays

From: Kees Cook
Date: Fri May 26 2023 - 22:10:33 EST


Fake flexible arrays have been deprecated since last millennium. Proper
C99 flexible arrays must be used throughout the kernel so
CONFIG_FORTIFY_SOURCE and CONFIG_UBSAN_BOUNDS can provide proper array
bounds checking.

Cc: Andy Whitcroft <apw@xxxxxxxxxxxxx>
Cc: Dwaipayan Ray <dwaipayanray1@xxxxxxxxx>
Cc: Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx>
Cc: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
Fixed-by: Joe Perches <joe@xxxxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230517204530.never.151-kees@xxxxxxxxxx
---
v3:
- Switch to ERROR from WARN
- drop needless struct/union/enum prefix (joe)
- fix $fixed regs (joe)
v2: https://lore.kernel.org/lkml/20230526173921.gonna.349-kees@xxxxxxxxxx
v1: https://lore.kernel.org/lkml/20230517204530.never.151-kees@xxxxxxxxxx
---
scripts/checkpatch.pl | 15 +++++++++++++++
1 file changed, 15 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 30b0b4fdb3bf..5307c85b93d8 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -7430,6 +7430,21 @@ sub process {
}
}

+# check for array definition/declarations that should use flexible arrays instead
+ if ($sline =~ /^[\+ ]\s*}\s*;\s*$/ &&
+ $prevline =~ /^\+\s*(?:\}|$Type)\s*$Ident\s*\[\s*(0|1)\s*\]\s*;\s*$/) {
+ if ($1 == '0') {
+ if (ERROR("ZERO_LENGTH_ARRAY",
+ "Use C99 flexible arrays instead of zero-length arrays - see https://github.com/KSPP/linux/issues/78\n"; . $hereprev) &&
+ $fix) {
+ $fixed[$fixlinenr - 1] =~ s/\[\s*0\s*\]/[]/;
+ }
+ } else {
+ ERROR("ONE_ELEMENT_ARRAY",
+ "Use C99 flexible arrays instead of one-element arrays - see https://github.com/KSPP/linux/issues/79\n"; . $hereprev);
+ }
+ }
+
# nested likely/unlikely calls
if ($line =~ /\b(?:(?:un)?likely)\s*\(\s*!?\s*(IS_ERR(?:_OR_NULL|_VALUE)?|WARN)/) {
WARN("LIKELY_MISUSE",
--
2.34.1