From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f41.google.com (mail-wm1-f41.google.com [209.85.128.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CF8982FD67F for ; Fri, 31 Oct 2025 16:54:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.41 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761929662; cv=none; b=erArFoyRE+B+9RW7jfiIHTfJnMwE6e5nAdfZEqsJRr3oIPyMcp3WImh571EnKYIuqodb6bV3FlU5GqCdxMINUOYMMfU+6V+8h88sHEdX9Hn1FulSJwp5Cql5NSmg5BR69SFUUQDpKfs558gRApQNHF8VDwekkWk0txPg+4fRqhA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761929662; c=relaxed/simple; bh=ic8R7PeSfgqiLUOO7h3/ggxGPF9WW8qd3pCh4Pyv/o0=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=cGa8n6HHDOZsjsnt5pp3giMaG9xH1H80BesLRqwCv0Tf+5z8Yb2rL5zonKLeoOPz6os0hzj2S0OUPd6Fq8MqQADx9av33je3nezKqMQGVzqQNCfHUvNpuyxFaruzTsD8wP+n4hjMqqtjZFlEnF67wGW/voSQl8SQhKGwzkHs+o0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=JYHWdcgP; arc=none smtp.client-ip=209.85.128.41 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="JYHWdcgP" Received: by mail-wm1-f41.google.com with SMTP id 5b1f17b1804b1-46e6a689bd0so24072595e9.1 for ; Fri, 31 Oct 2025 09:54:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1761929659; x=1762534459; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=q/vCylrs+0tr4q3q6ZAFpBo+ranVb22GkyacwbW2xw4=; b=JYHWdcgPCmH2iRM6bEUrof+ZjoGWLoyy8Xof68kJKJTfCwJC5XeqDeLxeAXk7zl4Dt MbNzxIUPE9WoZiXB8w/geNbQz+GI5E8B6DEcl3F4ZmDKOvMul+FUIRfu3QESHRR+8jFb w7orhtRA/6gziMhT/Yh/0i5/4ePQONjaGDw7ZvwM5l+wjUHDcljqr/AEgYVsxqIvCJ3N HsG9XpX3NdAgrxLYUBjPl92U6oK5Aw+YG50Q1l06DKmMNEzfkBF3Zo0y0P67I561pMVy 3zvvs9ouP5+LKKtpohlirUyIw5xvMwK7KH9o31IiamV9w1OuQtqP51Y5RxoK78LcRvEN WGOA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1761929659; x=1762534459; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=q/vCylrs+0tr4q3q6ZAFpBo+ranVb22GkyacwbW2xw4=; b=CWsWCP51fcsF4ebGjar7AZXf3wNgQhSe1RER8DiUJwSbiE4f4c2h96m3UEbtN1t+ta ie8qyq/q5CCnkSsckFHdubqfZNJ7C3Y+dQGSlW4TZtB1kZIUZn/GdV0kmfn+C0tqMp39 IrroQf7WDdpjpU2QT8I+xTVDUFW52OxI2vtd8kzGvNDvNIENHC1YCl5L1d8lL6BKyRdd S6T9wPoJCXy5TYQw8pvSZM2Bx/+tgLzmYr8X6V7hQaE+//dOulHtv7V6hUSEOCvNjdy/ CbpUFDrikTYwj5E5qqYtYvOwBSnsoVaYOLT073Q7tJ9X107jrmisHo/Nw+cv9qMSD/7m YWqQ== X-Forwarded-Encrypted: i=1; AJvYcCVvDew14Q4ZkJWcMkrahxWwsKg3SzHPpWBefFaWPAnPUrIMu+50c0JIJkNcewsEUtHZV3RORIodvTtMSa8=@vger.kernel.org X-Gm-Message-State: AOJu0Yye53fquziytAEHPMByC/b5T/zxtocFIHggDO/qPC+KIWFcjf/f cmTvkpCLIrFkigMQTTJ1xFgBujg7FEHWkgS/Bw49rAwYQV4qhUNYYxVy X-Gm-Gg: ASbGncvk38UEy/JVsrABvAO2EfmG4IEpyK5Chwjo+0XEKIa62uFTWwD0AbiJYynQH4D kU7VxKjXyUtbsBG87qhaUA5CvA6hdEbydl9uxd+vSo+RSa4yCliYBHkKaBpGIy+FfOk/pT8mMxl PrjxmI3emkNw1VWCoNeLhLHDEn/DRX7gRsNVpo1zbXDuJDXIGHC1zZqPk+CLE2LTEqlOK8tUZY9 dAdWQqpFL9+3vNdakvze2z1Av1qfjs+ObDSSmsdiBorW0G+vqV1zX/MAOzcEv0J/MnrB7tVDtAE oHM3FlsWRgMLeJRz+ITsn29AitRn/GXApO7h9DF4fkIkhmC7HGhwV393gs9/fCDj/rI1Kv7NeXu GmQJmQpir8EU63EjlfgrWlndMPfVD35Menmq0+jL/iqggGEV2z3NURbIHwTnWbZyNzdgQJ4v6On 3KSu4g7FF7I77lboK+DMe+8N3aN7ecnXeeheURv8cPmQ== X-Google-Smtp-Source: AGHT+IHSI+zsuHw2dropePAurzOFarCziEZZIfwNC9vETGbIZ+nr86tqW6LFJQrkhJOWJLe3kxpBzw== X-Received: by 2002:a05:600c:699a:b0:477:1326:7b4b with SMTP id 5b1f17b1804b1-47730872322mr45079395e9.19.1761929658835; Fri, 31 Oct 2025 09:54:18 -0700 (PDT) Received: from pumpkin (82-69-66-36.dsl.in-addr.zen.co.uk. [82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-429c13e03d0sm4564270f8f.26.2025.10.31.09.54.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 31 Oct 2025 09:54:18 -0700 (PDT) Date: Fri, 31 Oct 2025 16:54:17 +0000 From: David Laight To: Thorsten Blum Cc: Paul Moore , James Morris , "Serge E. Hallyn" , linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] device_cgroup: Replace strcpy/sprintf in set_majmin Message-ID: <20251031165417.4490941a@pumpkin> In-Reply-To: References: <20251031110647.102728-2-thorsten.blum@linux.dev> <20251031125916.3b0c8b22@pumpkin> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) 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=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 31 Oct 2025 16:23:02 +0100 Thorsten Blum wrote: > On 31. Oct 2025, at 13:59, David Laight wrote: > > Even if ex->major can be ~0 there are much cleaner ways of writing this code. > > Thanks for pointing this out. Looking at the bigger picture makes it > clear that most of the code can actually be removed. What do you think > of this change? That is sort of what I was thinking about, but it doesn't quite work. > > Thanks, > Thorsten > > diff --git a/security/device_cgroup.c b/security/device_cgroup.c > index a41f558f6fdd..cb845b1fad6b 100644 > --- a/security/device_cgroup.c > +++ b/security/device_cgroup.c > @@ -244,7 +244,6 @@ static void devcgroup_css_free(struct cgroup_subsys_state *css) > #define DEVCG_DENY 2 > #define DEVCG_LIST 3 > > -#define MAJMINLEN 13 > #define ACCLEN 4 > > static void set_access(char *acc, short access) > @@ -270,19 +269,11 @@ static char type_to_char(short type) > return 'X'; > } > > -static void set_majmin(char *str, unsigned m) > -{ > - if (m == ~0) > - strscpy(str, "*", MAJMINLEN); > - else > - snprintf(str, MAJMINLEN, "%u", m); > -} > - > static int devcgroup_seq_show(struct seq_file *m, void *v) > { > struct dev_cgroup *devcgroup = css_to_devcgroup(seq_css(m)); > struct dev_exception_item *ex; > - char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN]; > + char acc[ACCLEN]; > > rcu_read_lock(); > /* > @@ -293,17 +284,12 @@ static int devcgroup_seq_show(struct seq_file *m, void *v) > */ > if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { > set_access(acc, DEVCG_ACC_MASK); > - set_majmin(maj, ~0); > - set_majmin(min, ~0); > - seq_printf(m, "%c %s:%s %s\n", type_to_char(DEVCG_DEV_ALL), > - maj, min, acc); > + seq_printf(m, "%c *:* %s\n", type_to_char(DEVCG_DEV_ALL), acc); type_to_char(DEVCG_DEV_ALL) is 'a' and this is the only place it happens, also acc is "rwm". So that could be: seq_puts(m, "a *:* rwm\n"); > } else { > list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) { > set_access(acc, ex->access); > - set_majmin(maj, ex->major); > - set_majmin(min, ex->minor); > - seq_printf(m, "%c %s:%s %s\n", type_to_char(ex->type), > - maj, min, acc); > + seq_printf(m, "%c %u:%u %s\n", type_to_char(ex->type), > + ex->major, ex->minor, acc); It looks like both ex->major and ex->minor can be ~0. (I'm not sure it makes any sense to have major == ~0 and minor != ~0). However this should be ok: seq_putc(m, type_to_char(ex->type); if (ex->major == ~0) seq_puts(m, " *:"); else seq_printf(m, " %u:", ex->major); if (ex->minor == ~0) seq_puts(m, "* "); else seq_printf(m, "%u ", ex->minor); if (ex->access & DEVCG_ACC_READ) seq_putc(m, 'r'); if (ex->access & DEVCG_ACC_WRITE) seq_putc(m, 'w'); if (ex->access & DEV_ACC_MKNOD) seq_putc(m. 'm'); seq_putc(m, '\n'); A less intrusive change would be to pass 'm' the the set_xxx() functions and add the separators between the calls. David > } > } > rcu_read_unlock(); >