28 Feb
2012
28 Feb
'12
8:14 p.m.
Hi, I'm realizing that a doble freeing occurs in regex module when it
fails to start due to module params errors. But I'm sure it didn't
occur in Kamailio 1.5. My question is the following:
static int *number;
number = shm_malloc(sizeof(int));
shm_free(number);
Should now number be NULL? I confirm that it's NOT, so I get a double
freeing since the function free_shared_memory() is executed twice and
I check "if (number)" before doing "shm_free(number)".
So is it a change in 3.X? should I write:
shm_free(number);
number = NULL;
?
Thanks a lot.
--
Iñaki Baz Castillo
<ibc(a)aliax.net>
28 Feb
28 Feb
8:22 p.m.
Hello,
On 2/28/12 8:14 PM, Iñaki Baz Castillo wrote:
Hi, I'm realizing that a doble freeing occurs in
regex module when it
fails to start due to module params errors. But I'm sure it didn't
occur in Kamailio 1.5. My question is the following:
static int *number;
number = shm_malloc(sizeof(int));
shm_free(number);
Should now number be NULL? I confirm that it's NOT, so I get a double
freeing since the function free_shared_memory() is executed twice and
I check "if (number)" before doing "shm_free(number)".
So is it a change in 3.X? should I write:
shm_free(number);
number = NULL;
?
the pointer is not set to NULL, it never was, no matter the version and
name, since ser was started. Not even with system malloc, free does not
set it to null. One reason is that the pointer is given as parameter by
value, so the variable holding it cannot be changed. Well, in K,
shm_free() is a macro (define) and can be coded to set it to null, but
it is a risk if the parameter is an expression (e.g., computing the
pointer from: a start of a structure + offset).
To be able and safe to set it to null in a function, the parameter must
be a pointer to the pointer, like:
static int *number;
number = shm_malloc(sizeof(int));
my_shm_free(&number);
Cheers,
Daniel
--
Daniel-Constantin Mierla -- http://www.asipto.com
http://linkedin.com/in/miconda -- http://twitter.com/miconda
8:23 p.m.
2012/2/28 Daniel-Constantin Mierla <miconda(a)gmail.com>om>:
the pointer is not set to NULL, it never was, no
matter the version and
name, since ser was started. Not even with system malloc, free does not set
it to null. One reason is that the pointer is given as parameter by value,
so the variable holding it cannot be changed. Well, in K, shm_free() is a
macro (define) and can be coded to set it to null, but it is a risk if the
parameter is an expression (e.g., computing the pointer from: a start of a
structure + offset).
To be able and safe to set it to null in a function, the parameter must be a
pointer to the pointer, like:
static int *number;
number = shm_malloc(sizeof(int));
my_shm_free(&number);
Thanks a lot. Then there was a bug I will fix right now. Indeed
setting it to NULL does fix the problem.
--
Iñaki Baz Castillo
<ibc(a)aliax.net>
8:24 p.m.
You pass the value of a pointer, not the address of a pointer and
therefore it cannot be set to NULL.
You need to check if the shm_malloc is successful and before calling
shm_free, you should check the value of the pointer.
Also, it is always good to set the pointer to NULL after a shm_free to
avoid dangling pointers.
Regards,
Ovidiu Sas
On Tue, Feb 28, 2012 at 2:14 PM, Iñaki Baz Castillo <ibc(a)aliax.net> wrote:
Hi, I'm realizing that a doble freeing occurs in
regex module when it
fails to start due to module params errors. But I'm sure it didn't
occur in Kamailio 1.5. My question is the following:
static int *number;
number = shm_malloc(sizeof(int));
shm_free(number);
Should now number be NULL? I confirm that it's NOT, so I get a double
freeing since the function free_shared_memory() is executed twice and
I check "if (number)" before doing "shm_free(number)".
So is it a change in 3.X? should I write:
shm_free(number);
number = NULL;
?
Thanks a lot.
--
Iñaki Baz Castillo
<ibc(a)aliax.net>
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http://www.voipembedded.com
8:28 p.m.
2012/2/28 Ovidiu Sas <osas(a)voipembedded.com>om>:
You pass the value of a pointer, not the address of a
pointer and
therefore it cannot be set to NULL.
You need to check if the shm_malloc is successful and before calling
shm_free, you should check the value of the pointer.
Also, it is always good to set the pointer to NULL after a shm_free to
avoid dangling pointers.
Understood. That is exactly how it is now (will commit it right now).
Thanks a lot.
--
Iñaki Baz Castillo
<ibc(a)aliax.net>
11:20 a.m.
2012/2/29 Victor Seva <linuxmaniac(a)torreviejawireless.org>rg>:
2012/2/28 Iñaki Baz Castillo <ibc(a)aliax.net>et>:
[snip]
The commit fixes a specific bug:
In case regex module is provided with an invalid / non-existing pcres
file ("file" parameter) then a double freeing will occur when starting
kamailio (the daemon would fail anyway due to the bad config, but
without the fix it creates a coredump).
I will add it to 3.2 branch.
Thanks.
--
Iñaki Baz Castillo
<ibc(a)aliax.net>
Understood. That is exactly how it is now (will
commit it right now).
is this fix relevant for 3.2 branch too? Please merge the commit if it is.
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participants (4)
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Daniel-Constantin Mierla -
Iñaki Baz Castillo -
Ovidiu Sas -
Victor Seva