Re: [dpdk-dev] [PATCH] librte_cmdline: FreeBSD Fix oveflow when size of command result structure is greater than BUFSIZ

[Thomas Monjalon <thomas.monjalon@6wind.com>]

Hi Alan,

2014-10-20 15:26, Carew, Alan:
> A comment on my own patch.
> 
> Making the size of result_buf consistent across each OS and keeping it as large
> as the Linux BUFSIZ(8192) doesn't really address the core issue.
> 
> In the event that a user of librte_cmdline creates a custom context with a
> result structure > 8192 bytes then this problem will occur again, though 
> somewhat unlikely, as the minimum number of the largest type would be 64 x 
> cmdline_fixed_string_t types within a result structure, at its current size.
> 
> There is no checking of overflow, I would be tempted to add a runtime check in
> cmdline_parse()/match_inst(), however I would be more comfortable with a build
> time check for this type of problem.
> 
> Due to the opaque handling of user defined contexts there is no obvious way to
> do this at build time.
> 
> Thoughts?

librte_cmdline derivates from libcmdline written by Olivier Matz: 
	http://git.droids-corp.org/?p=libcmdline.git
Maybe there are some fixes to take here, and probably Olivier will have
some good insights.


> > -----Original Message-----
> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Alan Carew
> > Sent: Monday, October 20, 2014 4:23 PM
> > To: dev@dpdk.org
> > Subject: [dpdk-dev] [PATCH] librte_cmdline: FreeBSD Fix oveflow when size of
> > command result structure is greater than BUFSIZ
> > 
> > When using test-pmd with flow director in FreeBSD, the application will
> > segfault/Bus error while parsing the command-line. This is due to how
> > each commands result structure is represented during parsing, where the offsets
> > for each tokens value is stored in a character array(char result_buf[BUFSIZ])
> > in cmdline_parse()(./lib/librte_cmdline/cmdline_parse.c).
> > 
> > The overflow occurs where BUFSIZ is less than the size of a commands result
> > structure, in this case "struct cmd_pkt_filter_result"
> > (app/test-pmd/cmdline.c) is 1088 bytes and BUFSIZ on FreeBSD is 1024 bytes as
> > opposed to 8192 bytes on Linux.
> > 
> > This patch removes the OS dependency on BUFSIZ and defines and uses a
> > library #define CMDLINE_PARSE_RESULT_BUFSIZE 8192
> > 
> > The problem can be reproduced by running test-pmd on FreeBSD:
> > ./testpmd -c 0x3 -n 4 -- -i --portmask=0x3 --pkt-filter-mode=perfect
> > And adding a filter:
> > add_perfect_filter 0 udp src 192.168.0.0 1024 dst 192.168.0.0 1024 flexbytes
> > 0x800 vlan 0 queue 0 soft 0x17
> > 
> > Signed-off-by: Alan Carew <alan.carew@intel.com>
> > ---
> >  lib/librte_cmdline/cmdline_parse.c | 2 +-
> >  lib/librte_cmdline/cmdline_parse.h | 3 +++
> >  2 files changed, 4 insertions(+), 1 deletion(-)
[...]
> > --- a/lib/librte_cmdline/cmdline_parse.c
> > +++ b/lib/librte_cmdline/cmdline_parse.c
> > @@ -219,7 +219,7 @@ cmdline_parse(struct cmdline *cl, const char * buf)
> >  	unsigned int inst_num=0;
> >  	cmdline_parse_inst_t *inst;
> >  	const char *curbuf;
> > -	char result_buf[BUFSIZ];
> > +	char result_buf[CMDLINE_PARSE_RESULT_BUFSIZE];
[...]
> > --- a/lib/librte_cmdline/cmdline_parse.h
> > +++ b/lib/librte_cmdline/cmdline_parse.h
> > @@ -80,6 +80,9 @@ extern "C" {
> >  #define CMDLINE_PARSE_COMPLETE_AGAIN    1
> >  #define CMDLINE_PARSE_COMPLETED_BUFFER  2
> > 
> > +/* maximum buffer size for parsed result */
> > +#define CMDLINE_PARSE_RESULT_BUFSIZE 8192
> > +