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Subject[PATCH v5] checkpatch: Check for 0-length and 1-element arrays
Date
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@canonical.com>
Cc: Dwaipayan Ray <dwaipayanray1@gmail.com>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Fixed-by: Joe Perches <joe@perches.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20230517204530.never.151-kees@kernel.org
---
v5: - add __packed to outer struct regex too (joe)
v4: https://lore.kernel.org/lkml/20230531004929.you.436-kees@kernel.org
v3: https://lore.kernel.org/r/20230527020929.give.261-kees@kernel.org
v2: https://lore.kernel.org/lkml/20230526173921.gonna.349-kees@kernel.org
v1: https://lore.kernel.org/lkml/20230517204530.never.151-kees@kernel.org
---
scripts/checkpatch.pl | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 30b0b4fdb3bf..7bfa4d39d17f 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -7430,6 +7430,16 @@ sub process {
}
}

+# check for array definition/declarations that should use flexible arrays instead
+ if ($sline =~ /^[\+ ]\s*\}(?:\s*__packed)?\s*;\s*$/ &&
+ $prevline =~ /^\+\s*(?:\}(?:\s*__packed\s*)?|$Type)\s*$Ident\s*\[\s*(0|1)\s*\]\s*;\s*$/) {
+ if (ERROR("FLEXIBLE_ARRAY",
+ "Use C99 flexible arrays - see https://docs.kernel.org/process/deprecated.html#zero-length-and-one-element-arrays\n" . $hereprev) &&
+ $1 == '0' && $fix) {
+ $fixed[$fixlinenr - 1] =~ s/\[\s*0\s*\]/[]/;
+ }
+ }
+
# nested likely/unlikely calls
if ($line =~ /\b(?:(?:un)?likely)\s*\(\s*!?\s*(IS_ERR(?:_OR_NULL|_VALUE)?|WARN)/) {
WARN("LIKELY_MISUSE",
--
2.34.1
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