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Fri, 24 Apr 2026 11:50:01 -0700 (PDT) Date: Fri, 24 Apr 2026 21:52:12 +0300 From: Alexey Dobriyan To: Shengzhuo Wei Cc: Andrew Morton , John Stultz , Yao Zi , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH] proc: fix comm_write return value when truncated or error Message-ID: <5587b10e-91a4-458b-a95b-025be31e1a84@p183> References: <20260424-fix_proc_write_return-v1-1-7a793c2aad32@cherr.cc> <20260424035028.a811dd6bc8248b640a9fd7c2@linux-foundation.org> <3f91ed95-b38e-4049-b69c-13335b13ae44@p183> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Sat, Apr 25, 2026 at 02:03:41AM +0800, Shengzhuo Wei wrote: > On 2026-04-24 16:28, Alexey Dobriyan wrote: > > > > Fixes: 4614a696bd1c ("procfs: allow threads to rename siblings via /proc/pid/tasks/tid/comm") > > > > > > December 2009. > > > > > > Hopefully no userspace is depending on the broken return value of a > > > write to /proc/pid/comm. > > > > > > Arguably we should leave the code as-is and add an apologetic comment > > > explaining the situation. > > > > First, there's a plain bug regardless: assigning -EINVAL to a size_t count and > returning it as ssize_t produces a bogus positive value on the error path. There is no bug, write() will return -EINVAL as it should. > Introducing a dedicated ssize_t ret fixes this without changing any > success-path behavior, the change is on a permission failure path, so it's hard > to imagine anyone depending on the broken behavior, but worth mentioning