On 10/13/2014 06:47 PM, Alexander Graf wrote:
> On 13.10.14 16:36, Chen Gang wrote:
>> strncat() will append additional '\0' to destination buffer, so need
>> additional 1 byte for it, or may cause memory overflow, just like other
>> area within QEMU have done.
>>
>> Signed-off-by: Chen Gang <gang.chen.5i5j@xxxxxxxxx>
>
> I agree with this patch. However, the code is pretty ugly - I'm sure it
> must've been me who wrote it :).
>
> Could you please instead rewrite it to use g_strdup_printf() rather than
> strncat()s? That way we resolve all string pitfalls automatically - and
> this code is not the fast path, so doing an extra memory allocation is ok.
I'd just use snprintf() like this:
diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
index 9c23c6b..5eaa36c 100644
--- a/target-ppc/kvm.c
+++ b/target-ppc/kvm.c
@@ -1794,8 +1794,7 @@ static uint64_t kvmppc_read_int_cpu_dt(const char *propname)
return -1;
}
- strncat(buf, "/", sizeof(buf) - strlen(buf));
- strncat(buf, propname, sizeof(buf) - strlen(buf));
+ snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf), "/%s", propname);
f = fopen(buf, "rb");
if (!f) {
the buffer is of size PATH_MAX, and we're looking at /proc filesystem where
names should be rather short so we're extremly unlikely to hit this prob in
practice, there's no need to dynamically allocate a buffer for this stuff.
(Or alternatively there's asprintf(), but still I think it is overkill).
I can apply the above if everyone agrees.
Thanks,
/mjt
>> target-ppc/kvm.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
>> index 9c23c6b..66e7ce5 100644
>> --- a/target-ppc/kvm.c
>> +++ b/target-ppc/kvm.c
>> @@ -1794,8 +1794,8 @@ static uint64_t kvmppc_read_int_cpu_dt(const char *propname)
>> return -1;
>> }
>>
>> - strncat(buf, "/", sizeof(buf) - strlen(buf));
>> - strncat(buf, propname, sizeof(buf) - strlen(buf));
>> + strncat(buf, "/", sizeof(buf) - strlen(buf) - 1);
>> + strncat(buf, propname, sizeof(buf) - strlen(buf) - 1);
>>
>> f = fopen(buf, "rb");
>> if (!f) {
>>
>
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