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Fri, 13 Jul 2018 00:45:02 -0700 (PDT) Date: Fri, 13 Jul 2018 13:14:55 +0530 From: Himanshu Jha To: Dominique Martinet Cc: Michal Marek , Nicolas Palix , linux-kernel@vger.kernel.org, cocci@systeme.lip6.fr, Ville =?iso-8859-1?Q?Syrj=E4l=E4?= Subject: Re: [Cocci] [PATCH 01/18] coccinelle: change strncpy+truncation to strlcpy Message-ID: <20180713074455.GA6859@himanshu-Vostro-3559> References: <1531444483-17338-1-git-send-email-asmadeus@codewreck.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1531444483-17338-1-git-send-email-asmadeus@codewreck.org> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 13, 2018 at 03:14:43AM +0200, Dominique Martinet wrote: > Besides being simpler, using strlcpy instead of strncpy+truncation > fixes part of the following class of new gcc warnings: > > drivers/gpu/drm/i915/intel_tv.c: In function ‘intel_tv_get_modes’: > drivers/gpu/drm/i915/intel_tv.c:1358:3: error: ‘strncpy’ specified bound 32 equals > destination size [-Werror=stringop-truncation] > strncpy(mode_ptr->name, input->name, DRM_DISPLAY_MODE_LEN); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > cc1: all warnings being treated as errors > > Note that this is not a proper fix for this warning (and not all of the > occurences give the warning either - the strings are not always static). > The warning was intended to have developers check the return code of > strncpy and act in case of truncation (print a warning, abort the > function or something similar if the original string was not nul > terminated); the change to strlcpy only works because gcc does not > handle the function the same way. > > Suggested-by: Ville Syrjälä > Signed-off-by: Dominique Martinet > --- > > Running this fixes 30 occurences of the problem in 17 different > components of the kernel, and while the produced patches are fairly > straight-forward I'm not sure who I should expect to pick this up as > it is sent as a series. > I expect each maintainer will pick their share of the patchs if they > agree with it and the rest will just be dropped? Masahiro Yamada takes coccinelle patches, so please cc him or your patch would be lost. > .../coccinelle/misc/strncpy_truncation.cocci | 41 +++++++++++++++++++ > 1 file changed, 41 insertions(+) > create mode 100644 scripts/coccinelle/misc/strncpy_truncation.cocci > > diff --git a/scripts/coccinelle/misc/strncpy_truncation.cocci b/scripts/coccinelle/misc/strncpy_truncation.cocci > new file mode 100644 > index 000000000000..28b5c2a290ac > --- /dev/null > +++ b/scripts/coccinelle/misc/strncpy_truncation.cocci > @@ -0,0 +1,41 @@ > +/// Use strlcpy rather than strncpy(dest,..,sz) + dest[sz-1] = '\0' > +/// > +// Confidence: High > +// Comments: > +// Options: --no-includes --include-headers > + > +virtual patch > +virtual context You might consider adding context rule or remove this line perhaps ? > +virtual report > +virtual org > + > +@r@ > +expression dest, src, sz; > +position p; > +@@ > + > +strncpy@p(dest, src, sz); > +dest[sz - 1] = '\0'; > + > +@script:python depends on org@ > +p << r.p; > +@@ > + > +cocci.print_main("strncpy followed by truncation can be strlcpy",p) > + > +@script:python depends on report@ > +p << r.p; > +@@ > + > +msg = "SUGGESTION: strncpy followed by truncation can be strlcpy" > +coccilib.report.print_report(p[0],msg) > + > +@ok depends on patch@ > +expression r.dest, r.src, r.sz; > +position r.p; > +@@ > + > +-strncpy@p( > ++strlcpy( > + dest, src, sz); > +-dest[sz - 1] = '\0'; The above rule produces an output that I think is not correct: -------------------------------------------------------------- diff = diff -u -p a//ti/wl1251/acx.c b//ti/wl1251/acx.c --- a//ti/wl1251/acx.c +++ b//ti/wl1251/acx.c @@ -150,14 +150,7 @@ int wl1251_acx_fw_version(struct wl1251 } /* be careful with the buffer sizes */ - strncpy(buf, rev->fw_version, min(len, sizeof(rev->fw_version))); - - /* - * if the firmware version string is exactly - * sizeof(rev->fw_version) long or fw_len is less than - * sizeof(rev->fw_version) it won't be null terminated - */ - buf[min(len, sizeof(rev->fw_version)) - 1] = '\0'; + strlcpy(buf, rev->fw_version, min(len, sizeof(rev->fw_version))); ----------------------------------------------------------------- I think the comment is useful and should not be removed. Also, consider changing Confidence level appropriately. Thanks. -- Himanshu Jha Undergraduate Student Department of Electronics & Communication Guru Tegh Bahadur Institute of Technology