From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8A2D23D3D04; Fri, 24 Apr 2026 13:35:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777037732; cv=none; b=XhpevDIGVCgDV0wytRTUABCUhlS5a4y0IJuZ8ajGUT8iUy6vHaKJ+4YRjGHQ3+Cf29kgkx0qGZ3yNssy9knZMFL7HXOFzSUyyLN67//Fptj7uCi70isipgrZkpcGyW/byhLisbccnqrXwyqAZ+gMNzSSv1Ebja3HT5gE/5ehD5s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777037732; c=relaxed/simple; bh=H6sObuc8FxlRFqTOhDxEaZs0dJ92BAEP0F9ccpRvprI=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=p59WGwvQt4OD9jMcy4eMbZiitVWKEi7vMR6gFFyRLIAUB3FXBjoo/NvT7QP5pUcc8zrf9uTnxMBs8GIKhXT3ieaZhe/ICcTu55GKCUDep4+XfZzPp/71+6gWl71uek8tKUBa9N4blxhMXACzLdqU8jJvpC4EJDF2l18I/Aumeyc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=Sln3Pkmv; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="Sln3Pkmv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 05694C2BCB2; Fri, 24 Apr 2026 13:35:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1777037732; bh=H6sObuc8FxlRFqTOhDxEaZs0dJ92BAEP0F9ccpRvprI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Sln3PkmvyTZ5SOEYxrpV8ThqFzY2JbyL1G/on6R2lUmdrkJQoTo7FJc9EITQOUa+U U+qJXmh+ac8KW5pGC/EuXxkDEXh2GxehatRjy0V+AXtqVfa0H/bffWLUkGrq5sArJH LdFyf709VMrA5rz9x0WoDXhcKaCSXeTqKOPyn3QQ= Date: Fri, 24 Apr 2026 06:35:31 -0700 From: Andrew Morton To: "Shengzhuo Wei" Cc: "John Stultz" , "Yao Zi" , , , John Stultz Subject: Re: [PATCH] proc: fix comm_write return value when truncated or error Message-Id: <20260424063531.d1508a3c79c4b7808ed04420@linux-foundation.org> In-Reply-To: <20260424-fix_proc_write_return-v1-1-7a793c2aad32@cherr.cc> References: <20260424-fix_proc_write_return-v1-1-7a793c2aad32@cherr.cc> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 24 Apr 2026 04:06:21 +0800 "Shengzhuo Wei" wrote: > When count exceeds TASK_COMM_LEN-1, comm_write() copies at most > TASK_COMM_LEN-1 bytes but returns the original count. This violates > write(2) semantics, which require returning the number of bytes > actually written. > > The count parameter is size_t and should not be repurposed to carry a > negative error code on the same_thread_group() failure path. > > Introduce a local len for the truncated length and a separate ssize_t > ret for the return value. AI review asks a good question: https://sashiko.dev/#/patchset/20260424-fix_proc_write_return-v1-1-7a793c2aad32@cherr.cc