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[24.9.64.241]) by smtp.gmail.com with ESMTPSA id b8sm3866751iow.44.2021.01.25.18.38.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 25 Jan 2021 18:38:54 -0800 (PST) Subject: Re: [PATCH v4 11/17] selftests/resctrl: Enable gcc checks to detect buffer overflows To: Fenghua Yu , Shuah Khan , Tony Luck , Reinette Chatre , David Binderman , Babu Moger , James Morse , Ravi V Shankar , Shuah Khan Cc: linux-kernel References: <20201130202010.178373-1-fenghua.yu@intel.com> <20201130202010.178373-12-fenghua.yu@intel.com> From: Shuah Khan Message-ID: <11b8d4ef-c1ef-f00a-bf02-ea23e79065d6@linuxfoundation.org> Date: Mon, 25 Jan 2021 19:38:54 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <20201130202010.178373-12-fenghua.yu@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/30/20 1:20 PM, Fenghua Yu wrote: > David reported a buffer overflow error in the check_results() function of > the cmt unit test and he suggested enabling _FORTIFY_SOURCE gcc compiler > option to automatically detect any such errors. > > Feature Test Macros man page describes_FORTIFY_SOURCE as below > > "Defining this macro causes some lightweight checks to be performed to > detect some buffer overflow errors when employing various string and memory > manipulation functions (for example, memcpy, memset, stpcpy, strcpy, > strncpy, strcat, strncat, sprintf, snprintf, vsprintf, vsnprintf, gets, and > wide character variants thereof). For some functions, argument consistency > is checked; for example, a check is made that open has been supplied with a > mode argument when the specified flags include O_CREAT. Not all problems > are detected, just some common cases. > > If _FORTIFY_SOURCE is set to 1, with compiler optimization level 1 (gcc > -O1) and above, checks that shouldn't change the behavior of conforming > programs are performed. > > With _FORTIFY_SOURCE set to 2, some more checking is added, but some > conforming programs might fail. > > Some of the checks can be performed at compile time (via macros logic > implemented in header files), and result in compiler warnings; other checks > take place at run time, and result in a run-time error if the check fails. > > Use of this macro requires compiler support, available with gcc since > version 4.0." > > Fix the buffer overflow error in the check_results() function of the cmt > unit test and enable _FORTIFY_SOURCE gcc check to catch any future buffer > overflow errors. > > Reported-by: David Binderman > Suggested-by: David Binderman > Signed-off-by: Fenghua Yu > --- > tools/testing/selftests/resctrl/Makefile | 2 +- > tools/testing/selftests/resctrl/cmt_test.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/tools/testing/selftests/resctrl/Makefile b/tools/testing/selftests/resctrl/Makefile > index d585cc1948cc..6bcee2ec91a9 100644 > --- a/tools/testing/selftests/resctrl/Makefile > +++ b/tools/testing/selftests/resctrl/Makefile > @@ -1,5 +1,5 @@ > CC = $(CROSS_COMPILE)gcc > -CFLAGS = -g -Wall > +CFLAGS = -g -Wall -O2 -D_FORTIFY_SOURCE=2 > SRCS=$(wildcard *.c) > OBJS=$(SRCS:.c=.o) > > diff --git a/tools/testing/selftests/resctrl/cmt_test.c b/tools/testing/selftests/resctrl/cmt_test.c > index 188b73b5a2cc..ac1a33d9ce12 100644 > --- a/tools/testing/selftests/resctrl/cmt_test.c > +++ b/tools/testing/selftests/resctrl/cmt_test.c > @@ -81,7 +81,7 @@ static int check_results(struct resctrl_val_param *param, int no_of_bits) > return errno; > } > > - while (fgets(temp, 1024, fp)) { > + while (fgets(temp, sizeof(temp), fp)) { > char *token = strtok(temp, ":\t"); > int fields = 0; > > This should be fixed first before the other changes. thanks, -- Shuah