From mboxrd@z Thu Jan 1 00:00:00 1970 From: "J. Bruce Fields" Subject: Re: [PATCH] procfs: don't need a PATH_MAX allocation to hold a string representation of an int Date: Fri, 7 Sep 2012 15:44:16 -0400 Message-ID: <20120907194416.GB4633@fieldses.org> References: <1347021293-19052-1-git-send-email-jlayton@redhat.com> <20120907084814.07a59c98@corrin.poochiereds.net> <5049EF5B.3020607@draigBrady.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Jeff Layton , viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: =?utf-8?Q?P=C3=A1draig?= Brady Return-path: Content-Disposition: inline In-Reply-To: <5049EF5B.3020607@draigBrady.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Fri, Sep 07, 2012 at 01:58:03PM +0100, P=C3=A1draig 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 den= try *dentry, struct nameidata *nd) > >> pid_t tgid =3D task_tgid_nr_ns(current, ns); > >> char *name =3D ERR_PTR(-ENOENT); > >> if (tgid) { > >>- name =3D __getname(); > >>+ /* 10 for max length of an int in decimal + NULL terminator */ > >>+ name =3D 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 t= o > >express "strlen of max representation of an int in decimal" ? It'd be nice to have something--I've run across similar mistakes recently. >=20 > See INT_BUFSIZE_BOUND() in: > http://git.sv.gnu.org/gitweb/?p=3Dgnulib.git;a=3Dblob;f=3Dlib/intprop= s.h;hb=3DHEAD My lame attempt follows. It's simpler than P=C3=A1draig'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 =20 I've seen a couple examples recently where we've gotten this wrong. Maybe something like this would help? =20 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); =20 +/* + * 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 ar= gs); int bstr_printf(char *buf, size_t size, const char *fmt, const u32 *bi= n_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 =3D *ppos; size_t len; =20