From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753185Ab2IJO2o (ORCPT ); Mon, 10 Sep 2012 10:28:44 -0400 Received: from fieldses.org ([174.143.236.118]:42322 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752935Ab2IJO2n (ORCPT ); Mon, 10 Sep 2012 10:28:43 -0400 Date: Mon, 10 Sep 2012 10:28:37 -0400 From: "J. Bruce Fields" To: Jeff Layton Cc: =?utf-8?Q?P=C3=A1draig?= Brady , viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] procfs: don't need a PATH_MAX allocation to hold a string representation of an int Message-ID: <20120910142837.GB30136@fieldses.org> References: <1347021293-19052-1-git-send-email-jlayton@redhat.com> <20120907084814.07a59c98@corrin.poochiereds.net> <5049EF5B.3020607@draigBrady.com> <20120907194416.GB4633@fieldses.org> <20120910092328.0251144c@corrin.poochiereds.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20120910092328.0251144c@corrin.poochiereds.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 10, 2012 at 09:23:28AM -0400, Jeff Layton wrote: > On Fri, 7 Sep 2012 15:44:16 -0400 > "J. Bruce Fields" wrote: > > > On Fri, Sep 07, 2012 at 01:58:03PM +0100, Pádraig Brady wrote: > > > On 09/07/2012 01:48 PM, Jeff Layton wrote: > > > >On Fri, 7 Sep 2012 08:34:53 -0400 > > > >Jeff Layton wrote: > > > > > > > >>Signed-off-by: Jeff Layton > > > >>--- > > > >> fs/proc/base.c | 5 +++-- > > > >> 1 file changed, 3 insertions(+), 2 deletions(-) > > > >> > > > >>diff --git a/fs/proc/base.c b/fs/proc/base.c > > > >>index 1b6c84c..58e801b 100644 > > > >>--- a/fs/proc/base.c > > > >>+++ b/fs/proc/base.c > > > >>@@ -2758,7 +2758,8 @@ static void *proc_self_follow_link(struct dentry *dentry, struct nameidata *nd) > > > >> pid_t tgid = task_tgid_nr_ns(current, ns); > > > >> char *name = ERR_PTR(-ENOENT); > > > >> if (tgid) { > > > >>- name = __getname(); > > > >>+ /* 10 for max length of an int in decimal + NULL terminator */ > > > >>+ name = kmalloc(11, GFP_KERNEL); > > > > > > > > ^^^^^ > > > >Bah...my mistake. This should be "12", since it's possible (though > > > >unlikely) that this value could be negative. Is there a better way to > > > >express "strlen of max representation of an int in decimal" ? > > > > It'd be nice to have something--I've run across similar mistakes > > recently. > > > > > > > > See INT_BUFSIZE_BOUND() in: > > > http://git.sv.gnu.org/gitweb/?p=gnulib.git;a=blob;f=lib/intprops.h;hb=HEAD > > > > My lame attempt follows. It's simpler than Pádraig's but possibly also > > stupider. > > > > --b. > > > > commit 15e8c46104e0c1dd6a76d09b55563b6f83b61667 > > Author: J. Bruce Fields > > Date: Wed Aug 15 17:41:47 2012 -0400 > > > > strings: helper for maximum decimal encoding of an unsigned integer > > > > I've seen a couple examples recently where we've gotten this wrong. > > Maybe something like this would help? > > > > Suggested-by: Jim Rees > > Signed-off-by: J. Bruce Fields > > > > diff --git a/include/linux/string.h b/include/linux/string.h > > index ffe0442..3674cf5 100644 > > --- a/include/linux/string.h > > +++ b/include/linux/string.h > > @@ -126,6 +126,12 @@ extern void argv_free(char **argv); > > extern bool sysfs_streq(const char *s1, const char *s2); > > extern int strtobool(const char *s, bool *res); > > > > +/* > > + * length of the decimal representation of an unsigned integer. Just an > > + * approximation, but it's right for types of size 1 to 26 bytes: > > + */ > > +#define base10len(i) (sizeof(i) * 24 / 10 + 1) > > + > > #ifdef CONFIG_BINARY_PRINTF > > int vbin_printf(u32 *bin_buf, size_t size, const char *fmt, va_list args); > > int bstr_printf(char *buf, size_t size, const char *fmt, const u32 *bin_buf); > > diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c > > index 2afd2a8..1dcd2b3 100644 > > --- a/net/sunrpc/cache.c > > +++ b/net/sunrpc/cache.c > > @@ -1409,7 +1409,7 @@ static ssize_t read_flush(struct file *file, char __user *buf, > > size_t count, loff_t *ppos, > > struct cache_detail *cd) > > { > > - char tbuf[20]; > > + char tbuf[base10len(unsigned long) + 2]; > > unsigned long p = *ppos; > > size_t len; > > > > Thanks Bruce and Pádraig... > > Bruce, are you planning to push that patch for 3.7? If so, I'll base > mine on top of yours... I assumed string.h is outside my baliwick--I'm not sure where it should go. Linus or Andrew? --b.