[v2] lib/cfgfile: replace strcat with strlcat

Message ID 1552049150-5046-1-git-send-email-tallurix.chaitanya.babu@intel.com
State Accepted, archived
Delegated to: Thomas Monjalon
Headers show
Series
  • [v2] lib/cfgfile: replace strcat with strlcat
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Context Check Description
ci/intel-Performance-Testing success Performance Testing PASS
ci/mellanox-Performance-Testing success Performance Testing PASS
ci/Intel-compilation success Compilation OK
ci/checkpatch success coding style OK

Commit Message

Chaitanya Babu Talluri March 8, 2019, 12:45 p.m.
Replace strcat with strlcat to avoid buffer overflow.

Fixes: a6a47ac9c2 ("cfgfile: rework load function")
Cc: stable@dpdk.org

Signed-off-by: Chaitanya Babu Talluri <tallurix.chaitanya.babu@intel.com>
---
v2: Instead of strcat, used strlcat.
---
 lib/librte_cfgfile/rte_cfgfile.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Comments

Bruce Richardson March 8, 2019, 2:02 p.m. | #1
On Fri, Mar 08, 2019 at 12:45:50PM +0000, Chaitanya Babu Talluri wrote:
> Replace strcat with strlcat to avoid buffer overflow.
> 
> Fixes: a6a47ac9c2 ("cfgfile: rework load function")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Chaitanya Babu Talluri <tallurix.chaitanya.babu@intel.com>
> ---
> v2: Instead of strcat, used strlcat.
> ---
>  lib/librte_cfgfile/rte_cfgfile.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/librte_cfgfile/rte_cfgfile.c b/lib/librte_cfgfile/rte_cfgfile.c
> index 7d8c941ea..3296bb6f8 100644
> --- a/lib/librte_cfgfile/rte_cfgfile.c
> +++ b/lib/librte_cfgfile/rte_cfgfile.c
> @@ -8,6 +8,7 @@
>  #include <ctype.h>
>  #include <errno.h>
>  #include <rte_common.h>
> +#include <rte_string_fns.h>
>  
>  #include "rte_cfgfile.h"
>  
> @@ -224,10 +225,11 @@ rte_cfgfile_load_with_params(const char *filename, int flags,
>  			_strip(split[1], strlen(split[1]));
>  			char *end = memchr(split[1], '\\', strlen(split[1]));
>  
> +			size_t split_len = strlen(split[1]) + 1;
>  			while (end != NULL) {
>  				if (*(end+1) == params->comment_character) {
>  					*end = '\0';
> -					strcat(split[1], end+1);
> +					strlcat(split[1], end+1, split_len);

I don't think this will do what you want. Remember that strlcat takes the
total length of the buffer, which means that if split_len is set to the
current length (as you do before the while statement), then passing that
as the length parameter will cause strlcat to do nothing, since it sees the
buffer as already full.

/Bruce
Ferruh Yigit March 8, 2019, 5:30 p.m. | #2
On 3/8/2019 2:02 PM, Bruce Richardson wrote:
> On Fri, Mar 08, 2019 at 12:45:50PM +0000, Chaitanya Babu Talluri wrote:
>> Replace strcat with strlcat to avoid buffer overflow.
>>
>> Fixes: a6a47ac9c2 ("cfgfile: rework load function")
>> Cc: stable@dpdk.org
>>
>> Signed-off-by: Chaitanya Babu Talluri <tallurix.chaitanya.babu@intel.com>
>> ---
>> v2: Instead of strcat, used strlcat.
>> ---
>>  lib/librte_cfgfile/rte_cfgfile.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/lib/librte_cfgfile/rte_cfgfile.c b/lib/librte_cfgfile/rte_cfgfile.c
>> index 7d8c941ea..3296bb6f8 100644
>> --- a/lib/librte_cfgfile/rte_cfgfile.c
>> +++ b/lib/librte_cfgfile/rte_cfgfile.c
>> @@ -8,6 +8,7 @@
>>  #include <ctype.h>
>>  #include <errno.h>
>>  #include <rte_common.h>
>> +#include <rte_string_fns.h>
>>  
>>  #include "rte_cfgfile.h"
>>  
>> @@ -224,10 +225,11 @@ rte_cfgfile_load_with_params(const char *filename, int flags,
>>  			_strip(split[1], strlen(split[1]));
>>  			char *end = memchr(split[1], '\\', strlen(split[1]));
>>  
>> +			size_t split_len = strlen(split[1]) + 1;
>>  			while (end != NULL) {
>>  				if (*(end+1) == params->comment_character) {
>>  					*end = '\0';
>> -					strcat(split[1], end+1);
>> +					strlcat(split[1], end+1, split_len);
> 
> I don't think this will do what you want. Remember that strlcat takes the
> total length of the buffer, which means that if split_len is set to the
> current length (as you do before the while statement), then passing that
> as the length parameter will cause strlcat to do nothing, since it sees the
> buffer as already full.

The logic doesn't lengthen the 'split[1]' content, indeed it reduces the initial
size although it uses string concatenation, that is why it should be OK to use
'split_len' here.

What code does is, it finds specific char in 'split' buffer and removes it by
shifting remaining chars one byte to the left. So it shouldn't pass the initial
size of the buffer.

There is a overlapping strings concern, which 'strcat' & 'strlcat' don't
support, but I guess it is OK here since we are sure that strings are separated
by a NULL, so where a char read and written should be different although overall
dst and src buffers overlap.
Ferruh Yigit March 27, 2019, 11:37 a.m. | #3
On 3/26/2019 10:04 AM, Chaitanya Babu, TalluriX wrote:
> Hi 
> 
>> -----Original Message-----
>> From: Yigit, Ferruh
>> Sent: Friday, March 8, 2019 11:01 PM
>> To: Richardson, Bruce <bruce.richardson@intel.com>; Chaitanya Babu, TalluriX
>> <tallurix.chaitanya.babu@intel.com>
>> Cc: dev@dpdk.org; Pattan, Reshma <reshma.pattan@intel.com>;
>> Parthasarathy, JananeeX M <jananeex.m.parthasarathy@intel.com>;
>> Dumitrescu, Cristian <cristian.dumitrescu@intel.com>; stable@dpdk.org
>> Subject: Re: [PATCH v2] lib/cfgfile: replace strcat with strlcat
>>
>> On 3/8/2019 2:02 PM, Bruce Richardson wrote:
>>> On Fri, Mar 08, 2019 at 12:45:50PM +0000, Chaitanya Babu Talluri wrote:
>>>> Replace strcat with strlcat to avoid buffer overflow.
>>>>
>>>> Fixes: a6a47ac9c2 ("cfgfile: rework load function")
>>>> Cc: stable@dpdk.org
>>>>
>>>> Signed-off-by: Chaitanya Babu Talluri
>>>> <tallurix.chaitanya.babu@intel.com>
>>>> ---
>>>> v2: Instead of strcat, used strlcat.
>>>> ---
>>>>  lib/librte_cfgfile/rte_cfgfile.c | 4 +++-
>>>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/lib/librte_cfgfile/rte_cfgfile.c
>>>> b/lib/librte_cfgfile/rte_cfgfile.c
>>>> index 7d8c941ea..3296bb6f8 100644
>>>> --- a/lib/librte_cfgfile/rte_cfgfile.c
>>>> +++ b/lib/librte_cfgfile/rte_cfgfile.c
>>>> @@ -8,6 +8,7 @@
>>>>  #include <ctype.h>
>>>>  #include <errno.h>
>>>>  #include <rte_common.h>
>>>> +#include <rte_string_fns.h>
>>>>
>>>>  #include "rte_cfgfile.h"
>>>>
>>>> @@ -224,10 +225,11 @@ rte_cfgfile_load_with_params(const char
>> *filename, int flags,
>>>>  			_strip(split[1], strlen(split[1]));
>>>>  			char *end = memchr(split[1], '\\', strlen(split[1]));
>>>>
>>>> +			size_t split_len = strlen(split[1]) + 1;
>>>>  			while (end != NULL) {
>>>>  				if (*(end+1) == params->comment_character)
>> {
>>>>  					*end = '\0';
>>>> -					strcat(split[1], end+1);
>>>> +					strlcat(split[1], end+1, split_len);
>>>
>>> I don't think this will do what you want. Remember that strlcat takes
>>> the total length of the buffer, which means that if split_len is set
>>> to the current length (as you do before the while statement), then
>>> passing that as the length parameter will cause strlcat to do nothing,
>>> since it sees the buffer as already full.
>>
>> The logic doesn't lengthen the 'split[1]' content, indeed it reduces the initial
>> size although it uses string concatenation, that is why it should be OK to use
>> 'split_len' here.
>>
>> What code does is, it finds specific char in 'split' buffer and removes it by
>> shifting remaining chars one byte to the left. So it shouldn't pass the initial size
>> of the buffer.
>>
>> There is a overlapping strings concern, which 'strcat' & 'strlcat' don't support,
>> but I guess it is OK here since we are sure that strings are separated by a
>> NULL, so where a char read and written should be different although overall
>> dst and src buffers overlap.
> 
> Yes, although the same string is manipulated the split string (*end = '\0') is separated with NULL.
> Strlcat works fine here and expected concatenation  is happening.
> If there are no further comments request for ACK please.

Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>
Thomas Monjalon April 5, 2019, 12:53 p.m. | #4
27/03/2019 12:37, Ferruh Yigit:
> On 3/26/2019 10:04 AM, Chaitanya Babu, TalluriX wrote:
> > From: Yigit, Ferruh
> >> On 3/8/2019 2:02 PM, Bruce Richardson wrote:
> >>> On Fri, Mar 08, 2019 at 12:45:50PM +0000, Chaitanya Babu Talluri wrote:
> >>>> Replace strcat with strlcat to avoid buffer overflow.
> >>>>
> >>>> Fixes: a6a47ac9c2 ("cfgfile: rework load function")
> >>>> Cc: stable@dpdk.org
> >>>>
> >>>> Signed-off-by: Chaitanya Babu Talluri
> >>>> <tallurix.chaitanya.babu@intel.com>
> >>>> ---
> >>>> @@ -224,10 +225,11 @@ rte_cfgfile_load_with_params(const char
> >> *filename, int flags,
> >>>>  			_strip(split[1], strlen(split[1]));
> >>>>  			char *end = memchr(split[1], '\\', strlen(split[1]));
> >>>>
> >>>> +			size_t split_len = strlen(split[1]) + 1;
> >>>>  			while (end != NULL) {
> >>>>  				if (*(end+1) == params->comment_character)
> >> {
> >>>>  					*end = '\0';
> >>>> -					strcat(split[1], end+1);
> >>>> +					strlcat(split[1], end+1, split_len);
> >>>
> >>> I don't think this will do what you want. Remember that strlcat takes
> >>> the total length of the buffer, which means that if split_len is set
> >>> to the current length (as you do before the while statement), then
> >>> passing that as the length parameter will cause strlcat to do nothing,
> >>> since it sees the buffer as already full.
> >>
> >> The logic doesn't lengthen the 'split[1]' content, indeed it reduces the initial
> >> size although it uses string concatenation, that is why it should be OK to use
> >> 'split_len' here.
> >>
> >> What code does is, it finds specific char in 'split' buffer and removes it by
> >> shifting remaining chars one byte to the left. So it shouldn't pass the initial size
> >> of the buffer.
> >>
> >> There is a overlapping strings concern, which 'strcat' & 'strlcat' don't support,
> >> but I guess it is OK here since we are sure that strings are separated by a
> >> NULL, so where a char read and written should be different although overall
> >> dst and src buffers overlap.
> > 
> > Yes, although the same string is manipulated the split string (*end = '\0') is separated with NULL.
> > Strlcat works fine here and expected concatenation  is happening.
> > If there are no further comments request for ACK please.
> 
> Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>

Applied, thanks

Patch

diff --git a/lib/librte_cfgfile/rte_cfgfile.c b/lib/librte_cfgfile/rte_cfgfile.c
index 7d8c941ea..3296bb6f8 100644
--- a/lib/librte_cfgfile/rte_cfgfile.c
+++ b/lib/librte_cfgfile/rte_cfgfile.c
@@ -8,6 +8,7 @@ 
 #include <ctype.h>
 #include <errno.h>
 #include <rte_common.h>
+#include <rte_string_fns.h>
 
 #include "rte_cfgfile.h"
 
@@ -224,10 +225,11 @@  rte_cfgfile_load_with_params(const char *filename, int flags,
 			_strip(split[1], strlen(split[1]));
 			char *end = memchr(split[1], '\\', strlen(split[1]));
 
+			size_t split_len = strlen(split[1]) + 1;
 			while (end != NULL) {
 				if (*(end+1) == params->comment_character) {
 					*end = '\0';
-					strcat(split[1], end+1);
+					strlcat(split[1], end+1, split_len);
 				} else
 					end++;
 				end = memchr(end, '\\', strlen(end));