From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joe Perches Subject: Re: [PATCH -next 2/3] batman-adv: Use seq_overflow Date: Wed, 11 Dec 2013 00:26:17 -0800 Message-ID: <1386750377.8168.37.camel@joe-AO722> References: <20131211075526.GR10323@ZenIV.linux.org.uk> <20131211080504.GT10323@ZenIV.linux.org.uk> Reply-To: The list for a Better Approach To Mobile Ad-hoc Networking Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Cc: Kees Cook , netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, b.a.t.m.a.n-ZwoEplunGu2X36UT3dwllkB+6BGkLq7r@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Antonio Quartulli , "David S. Miller" , Marek Lindner To: Al Viro Return-path: In-Reply-To: <20131211080504.GT10323-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: b.a.t.m.a.n-bounces-ZwoEplunGu2X36UT3dwllkB+6BGkLq7r@public.gmane.org Sender: "B.A.T.M.A.N" List-Id: netdev.vger.kernel.org On Wed, 2013-12-11 at 08:05 +0000, Al Viro wrote: > On Wed, Dec 11, 2013 at 07:55:26AM +0000, Al Viro wrote: > > > This sucker should return 0. Insufficiently large buffer will be handled > > by caller, TYVM, if you give that caller a chance to do so. Returning 1 > > from ->show() is a bug in almost all cases, and definitely so in this one. > > > > Just in case somebody decides that above is worth copying: It Is Not. > > Original code is buggy, plain and simple. This one trades the older > > bug ("fail with -EINVAL whenever the buffer is too small") with just as buggy > > "silently skip an entry entirely whenever the buffer is too small". > > > > Don't Do That. > > Pardon - Joe has made seq_overflow return -1 instead of true. Correction > to the above, then - s/This trades.*\./This is just as buggy./ Yeah, I started to use true/false, 0/1, but thought I needed to match what seq_printf/seq_vprintf does. > Conclusion is still the same - Don't Do That. Returning -1 on insufficiently > large buffer is a bug, plain and simple. int seq_vprintf(struct seq_file *m, const char *f, va_list args) { int len; if (m->count < m->size) { len = vsnprintf(m->buf + m->count, m->size - m->count, f, args); if (m->count + len < m->size) { m->count += len; return 0; } } seq_set_overflow(m); return -1; } EXPORT_SYMBOL(seq_vprintf); int seq_printf(struct seq_file *m, const char *f, ...) { int ret; va_list args; va_start(args, f); ret = seq_vprintf(m, f, args); va_end(args); return ret; } EXPORT_SYMBOL(seq_printf); > And this patch series is completely misguided - it doesn't fix any bugs > *and* it provides a misleading example for everyone. See the reaction > right in this thread, proposing to spread the same bug to currently > working iterators. Anyway, changing seq_overflow is easy enough You prefer this? bool seq_overflow(struct seq_file *seq) { return m->count == m->size; }