From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ryan Mallon Subject: Re: [PATCH][REPOST] Check maxlen on strnlen_user usage Date: Thu, 08 Sep 2011 10:20:45 +1000 Message-ID: <4E680A5D.7050903@gmail.com> References: <4E68042A.1050406@gmail.com> <20110907170621.389b1314.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Mark Salter , Alexander Viro , linux-fsdevel@vger.kernel.org, "linux-kernel@vger.kernel.org" , "trivial@kernel.org" To: Andrew Morton Return-path: Received: from mail-gy0-f174.google.com ([209.85.160.174]:52289 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756373Ab1IHAUw (ORCPT ); Wed, 7 Sep 2011 20:20:52 -0400 In-Reply-To: <20110907170621.389b1314.akpm@linux-foundation.org> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On 08/09/11 10:06, Andrew Morton wrote: > On Thu, 08 Sep 2011 09:54:18 +1000 > Ryan Mallon wrote: > >> strnlen_user returns the length of the string including the nul >> terminator. In the case where maxlen is reached strnlen_user returns >> maxlen + 1. Most callsites already check for this condition. Fix the >> call to strnlen_user in fs/exec.c to check for the maxlen case. >> >> diff --git a/fs/exec.c b/fs/exec.c >> index 25dcbe5..e19588c 100644 >> --- a/fs/exec.c >> +++ b/fs/exec.c >> @@ -481,7 +481,7 @@ static int copy_strings(int argc, struct >> user_arg_ptr argv, >> goto out; >> >> len = strnlen_user(str, MAX_ARG_STRLEN); >> - if (!len) >> + if (!len || len> MAX_ARG_STRLEN) >> goto out; >> >> ret = -E2BIG; > The following call to vald_arg_len() already does this? > > This change will cause copy_strings() to incorrectly return -EFAULT, > rather than -E2BIG. Hmm, missed that. How about the patch below instead which passes the correct length to strnlen_user? > Your email client is wordwrapping and space-stuffing the patches, btw. I'll try again. Hopefully it works this time. --- Replace valid_arg_len function in fs/exec.c with max_arg_len function and pass the correct length to strnlen_user. Signed-off-by: Ryan Mallon --- diff --git a/fs/exec.c b/fs/exec.c index e19588c..12d2f7f 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -296,9 +296,9 @@ err: return err; } -static bool valid_arg_len(struct linux_binprm *bprm, long len) +static long max_arg_len(struct linux_binprm *bprm) { - return len<= MAX_ARG_STRLEN; + return MAX_ARG_STRLEN; } #else @@ -354,9 +354,9 @@ static int __bprm_mm_init(struct linux_binprm *bprm) return 0; } -static bool valid_arg_len(struct linux_binprm *bprm, long len) +static long max_arg_len(struct linux_binprm *bprm) { - return len<= bprm->p; + return bprm->p; } #endif /* CONFIG_MMU */ @@ -474,18 +474,19 @@ static int copy_strings(int argc, struct user_arg_ptr argv, const char __user *str; int len; unsigned long pos; + long max_len = max_arg_len(bprm); ret = -EFAULT; str = get_user_arg_ptr(argv, argc); if (IS_ERR(str)) goto out; - len = strnlen_user(str, MAX_ARG_STRLEN); - if (!len || len> MAX_ARG_STRLEN) + len = strnlen_user(str, max_len); + if (!len) goto out; ret = -E2BIG; - if (!valid_arg_len(bprm, len)) + if (len> max_len) goto out; /* We're going to work our way backwords. */