LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Jiri Olsa <jolsa@redhat.com>
To: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>, Ben Gainey <ben.gainey@arm.com>,
	Stephane Eranian <eranian@google.com>,
	lkml <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: [PATCHv2] perf jvmti: Fix gcc string overflow warning
Date: Fri, 31 May 2019 15:13:21 +0200
Message-ID: <20190531131321.GB1281@krava> (raw)
In-Reply-To: <20190531120530.GB17152@kernel.org>

On Fri, May 31, 2019 at 09:05:30AM -0300, Arnaldo Carvalho de Melo wrote:

SNIP

> The kernel folks moved beyond that and in lib/string.c we have:
> 
> /**
>  * strscpy - Copy a C-string into a sized buffer
>  * @dest: Where to copy the string to
>  * @src: Where to copy the string from
>  * @count: Size of destination buffer
>  *
>  * Copy the string, or as much of it as fits, into the dest buffer.  The
>  * behavior is undefined if the string buffers overlap.  The destination
>  * buffer is always NUL terminated, unless it's zero-sized.
>  *
>  * Preferred to strlcpy() since the API doesn't require reading memory
>  * from the src string beyond the specified "count" bytes, and since
>  * the return value is easier to error-check than strlcpy()'s.
>  * In addition, the implementation is robust to the string changing out
>  * from underneath it, unlike the current strlcpy() implementation.
>  *
>  * Preferred to strncpy() since it always returns a valid string, and
>  * doesn't unnecessarily force the tail of the destination buffer to be
>  * zeroed.  If zeroing is desired please use strscpy_pad().
>  *
>  * Return: The number of characters copied (not including the trailing
>  *         %NUL) or -E2BIG if the destination buffer wasn't big enough.
>  */
> ssize_t strscpy(char *dest, const char *src, size_t count)
> 
> 
> 
> I think for these needs flipping that 'n' into a 'l' is good enough.

ok, I forgot there's strlcpy.. v2 attached

thanks,
jirka


---
We are getting fake gcc warning when we compile with gcc9 (9.1.1):

     CC       jvmti/libjvmti.o
   In file included from /usr/include/string.h:494,
                    from jvmti/libjvmti.c:5:
   In function ‘strncpy’,
       inlined from ‘copy_class_filename.constprop’ at jvmti/libjvmti.c:166:3:
   /usr/include/bits/string_fortified.h:106:10: error: ‘__builtin_strncpy’ specified bound depends on the length of the source argument [-Werror=stringop-overflow=]
     106 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest));
         |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   jvmti/libjvmti.c: In function ‘copy_class_filename.constprop’:
   jvmti/libjvmti.c:165:26: note: length computed here
     165 |   size_t file_name_len = strlen(file_name);
         |                          ^~~~~~~~~~~~~~~~~
   cc1: all warnings being treated as errors

As per Arnaldo's suggestion using strlcpy, which does
the same thing and keeps gcc silent.

Cc: Ben Gainey <ben.gainey@arm.com>
Cc: Stephane Eranian <eranian@google.com>
Suggested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: http://lkml.kernel.org/n/tip-sve3b63c550wr907e6ui6gx5@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 tools/perf/jvmti/libjvmti.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/jvmti/libjvmti.c b/tools/perf/jvmti/libjvmti.c
index aea7b1fe85aa..c441a34cb1c0 100644
--- a/tools/perf/jvmti/libjvmti.c
+++ b/tools/perf/jvmti/libjvmti.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/compiler.h>
+#include <linux/string.h>
 #include <sys/types.h>
 #include <stdio.h>
 #include <string.h>
@@ -162,8 +163,7 @@ copy_class_filename(const char * class_sign, const char * file_name, char * resu
 		result[i] = '\0';
 	} else {
 		/* fallback case */
-		size_t file_name_len = strlen(file_name);
-		strncpy(result, file_name, file_name_len < max_length ? file_name_len : max_length);
+		strlcpy(result, file_name, max_length);
 	}
 }
 
-- 
2.21.0


  reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-31  8:03 [PATCH] " Jiri Olsa
2019-05-31 12:05 ` Arnaldo Carvalho de Melo
2019-05-31 13:13   ` Jiri Olsa [this message]
2019-06-05 12:53     ` [PATCHv2] " Arnaldo Carvalho de Melo
2019-06-17 19:15     ` [tip:perf/core] perf jvmti: Address gcc string overflow warning for strncpy() tip-bot for Jiri Olsa
2019-07-09 11:33     ` tip-bot for Jiri Olsa

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190531131321.GB1281@krava \
    --to=jolsa@redhat.com \
    --cc=a.p.zijlstra@chello.nl \
    --cc=acme@kernel.org \
    --cc=alexander.shishkin@linux.intel.com \
    --cc=ben.gainey@arm.com \
    --cc=eranian@google.com \
    --cc=jolsa@kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@kernel.org \
    --cc=namhyung@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
	git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git