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[204.195.123.141]) by smtp.gmail.com with ESMTPSA id ks21-20020a056a004b9500b006dac91d55f7sm10314445pfb.136.2024.01.22.16.43.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Jan 2024 16:43:37 -0800 (PST) Date: Mon, 22 Jan 2024 16:43:36 -0800 From: Stephen Hemminger To: Pedro Tammela Cc: netdev@vger.kernel.org Subject: Re: [PATCH iproute2 1/2] color: use empty format string instead of NULL in vfprintf Message-ID: <20240122164336.12119994@hermes.local> In-Reply-To: <20240122210546.3423784-2-pctammela@mojatatu.com> References: <20240122210546.3423784-1-pctammela@mojatatu.com> <20240122210546.3423784-2-pctammela@mojatatu.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 22 Jan 2024 18:05:45 -0300 Pedro Tammela wrote: > NULL is passed in the format string when nothing is to be printed. > This is commonly done in the print_bool function when a flag is false. > Glibc seems to handle this case nicely but for musl it will cause a > segmentation fault. > > The following is an example of one crash in musl based systems/containers: > tc qdisc add dev dummy0 handle 1: root choke limit 1000 bandwidth 10000 > tc qdisc replace dev dummy0 handle 1: root choke limit 1000 bandwidth 10000 min 100 > tc qdisc show dev dummy0 > > Signed-off-by: Pedro Tammela > --- > lib/color.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Wouldn't it be simpler to just add a short circuit check. This would fix the color case as well. diff --git a/lib/color.c b/lib/color.c index 59976847295c..cd0f9f7509b5 100644 --- a/lib/color.c +++ b/lib/color.c @@ -140,6 +140,9 @@ int color_fprintf(FILE *fp, enum color_attr attr, const char *fmt, ...) int ret = 0; va_list args; + if (fmt == NULL) + return 0; + va_start(args, fmt); if (!color_is_enabled || attr == COLOR_NONE) {