From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH 04/28] libxl: fix libxl_string_list_length and its only caller Date: Thu, 26 Sep 2013 20:37:15 +0100 Message-ID: <52448CEB.9050109@citrix.com> References: <1379475484-25993-1-git-send-email-mattjd@gmail.com> <1379475484-25993-5-git-send-email-mattjd@gmail.com> <52448B0A.6030808@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <52448B0A.6030808@oracle.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Boris Ostrovsky Cc: Ian Campbell , Stefano Stabellini , Matthew Daley , Ian Jackson , xen-devel@lists.xen.org, David Vrabel List-Id: xen-devel@lists.xenproject.org On 26/09/13 20:29, Boris Ostrovsky wrote: > On 09/17/2013 11:37 PM, Matthew Daley wrote: >> The wrong amount of indirections were being taken in >> libxl_string_list_length, and its only caller was miscounting the amount >> of initial non-list arguments, seemingly since the initial commit >> (599c784). >> >> This has been seen and reported in the wild (##xen): >> < Trixboxer> Hi, any idea why would I get >> < Trixboxer> xl: libxl_bootloader.c:42: bootloader_arg: Assertion >> `bl->nargs < bl->argsspace' failed. >> < Trixboxer> 4.2.2-23.el6 >> >> Coverity-ID: 1054954 >> Signed-off-by: Matthew Daley >> --- >> tools/libxl/libxl.c | 2 +- >> tools/libxl/libxl_bootloader.c | 2 +- >> 2 files changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c >> index 0879f23..ca24ca3 100644 >> --- a/tools/libxl/libxl.c >> +++ b/tools/libxl/libxl.c >> @@ -202,7 +202,7 @@ int libxl_string_list_length(const >> libxl_string_list *psl) >> { >> if (!psl) return 0; > > This should be > if (!psl || !(*psl)) return 0; > > We segfault otherwise at the changed line below if no arguments are > passed to the bootloader (as is the case with pvgrub). > >> int i = 0; >> - while (*psl++) i++; >> + while ((*psl)[i]) i++; >> return i; >> } > > (I am surprised Coverity didn't flag this) > > -boris For this bug, Coveritys specific objection was that the caller passes a singleton pointer into this function, and this function uses it as an array. This is a side effect of using the wrong indirection. However, your spot of the crash is good, and needs fixing as well. ~Andrew