On Mon, 2014-01-27 at 16:39 -0800, Kees Cook wrote:
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
[]
> @@ -1735,14 +1735,10 @@ int vsnprintf(char *buf, size_t size, const char
> *fmt, va_list args)
> case FORMAT_TYPE_NRCHARS: {
> /*
> * Since %n poses a greater security risk than
> - * utility, ignore %n and skip its argument.
> + * utility, it should not be implemented. Instead,
> + * when encountering %n, ignore the arguments.
> */
> - void *skip_arg;
> -
> - WARN_ONCE(1, "Please remove ignored %%n in '%s'\n",
> - old_fmt);
> -
> - skip_arg = va_arg(args, void *);
> + WARN_ONCE(1, "Ignored %%n in '%s'\n", old_fmt);
> break;
> }
I don't think this is better either.
Why not tell people to fix the code?
checkpatch isn't run on quite a lot of patches.
anyway, here's a possible checkpatch test too.
---
scripts/checkpatch.pl | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 1dbd6d1..95c3264 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -4069,6 +4069,15 @@ sub process {
}
}
+# check for unsupported uses of %n in what appear to be formats
+ if ($sline =~ /\b$logFunctions\s*\(.*"/) {
+ my $fmt = get_quoted_string($line, $rawline);
+ if ($fmt ne "" && $fmt =~ /[^\%]\%n/) {
+ WARN("PRINTF_CONTROL_N",
+ "printf style use of \%n is not
supported\n" . $herecurr);
+ }
+ }
+
# Check for misused memsets
if ($^V && $^V ge 5.10.0 &&
defined $stat &&
--
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