From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 11 Dec 2013 08:05:04 +0000 From: Al Viro Message-ID: <20131211080504.GT10323@ZenIV.linux.org.uk> References: <20131211075526.GR10323@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131211075526.GR10323@ZenIV.linux.org.uk> Sender: Al Viro Subject: Re: [B.A.T.M.A.N.] [PATCH -next 2/3] batman-adv: Use seq_overflow Reply-To: The list for a Better Approach To Mobile Ad-hoc Networking List-Id: The list for a Better Approach To Mobile Ad-hoc Networking List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Joe Perches Cc: Kees Cook , netdev@vger.kernel.org, b.a.t.m.a.n@lists.open-mesh.org, linux-kernel@vger.kernel.org, Antonio Quartulli , "David S. Miller" , Marek Lindner 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./ Conclusion is still the same - Don't Do That. Returning -1 on insufficiently large buffer is a bug, plain and simple. 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.