Re: [PATCH] cutils: fix memory leak in get_relocated_path()

From: Stefano Garzarella <sgarzare@redhat.com>
To: "Philippe Mathieu-Daudé" <philmd@redhat.com>
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
	"Alex Bennée" <alex.bennee@linaro.org>,
	qemu-devel@nongnu.org
Subject: Re: [PATCH] cutils: fix memory leak in get_relocated_path()
Date: Tue, 13 Apr 2021 13:47:42 +0200	[thread overview]
Message-ID: <20210413114742.i7bu2sc2w6ityjic@steredhat> (raw)
In-Reply-To: <22828e2d-2c8e-c753-31e5-7588f9064b10@redhat.com>

On Tue, Apr 13, 2021 at 12:59:36PM +0200, Philippe Mathieu-Daudé wrote:
>Is this fix aiming at 6.0 release?

The leak is minimal, but the fix is very simple.
So, I think it can go if someone has a pull request to send with other 
patches, but I'm not sure with which tree.

Thanks,
Stefano

>
>On 4/12/21 7:02 PM, Stefano Garzarella wrote:
>> get_relocated_path() allocates a GString object and returns the
>> character data (C string) to the caller without freeing the memory
>> allocated for that object as reported by valgrind:
>>
>>   24 bytes in 1 blocks are definitely lost in loss record 2,805 of 6,532
>>      at 0x4839809: malloc (vg_replace_malloc.c:307)
>>      by 0x55AABB8: g_malloc (in /usr/lib64/libglib-2.0.so.0.6600.8)
>>      by 0x55C2481: g_slice_alloc (in /usr/lib64/libglib-2.0.so.0.6600.8)
>>      by 0x55C4827: g_string_sized_new (in /usr/lib64/libglib-2.0.so.0.6600.8)
>>      by 0x55C4CEA: g_string_new (in /usr/lib64/libglib-2.0.so.0.6600.8)
>>      by 0x906314: get_relocated_path (cutils.c:1036)
>>      by 0x6E1F77: qemu_read_default_config_file (vl.c:2122)
>>      by 0x6E1F77: qemu_init (vl.c:2687)
>>      by 0x3E3AF8: main (main.c:49)
>>
>> Let's use g_string_free(gstring, false) to free only the GString object
>> and transfer the ownership of the character data to the caller.
>>
>> Fixes: f4f5ed2cbd ("cutils: introduce get_relocated_path")
>> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
>> ---
>>  util/cutils.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/util/cutils.c b/util/cutils.c
>> index ee908486da..c9b91e7535 100644
>> --- a/util/cutils.c
>> +++ b/util/cutils.c
>> @@ -1055,5 +1055,5 @@ char *get_relocated_path(const char *dir)
>>          assert(G_IS_DIR_SEPARATOR(dir[-1]));
>>          g_string_append(result, dir - 1);
>>      }
>> -    return result->str;
>> +    return g_string_free(result, false);
>>  }
>>
>