Re: [lwip-devel] [EXTERNAL] [bug #61126] ram_end write outside heap...

[Dag Midling Larsen]

Hi

Now I have read the lines [373, 381] in mem.c and understand what you mean.
So I could agree that it's not a bug, but it's an implementation which invites 
for unstable code for the users.
Problem is that (many) users normally don't read .c files/implementation unless 
there is a problem or issue.

An example of how an issue sneaks in:
St, a microcontroller provider has this lots of example projects. E.g. this:
STM32Cube\Repository\STM32Cube_FW_H7_V1.8.0\Projects\NUCLEO-H743ZI\Applications\LwIP\LwIP_HTTP_Server_Netconn_RTOS
This example project lwipopts.h has these lines:
-----
/* MEM_SIZE: the size of the heap memory. If the application will send
a lot of data that needs to be copied, this should be set high. */
#define MEM_SIZE                (10*1024)

/* Relocate the LwIP RAM heap pointer */
#define LWIP_RAM_HEAP_POINTER    (0x30044000)
-----

Now lwip mem.c implementation writes outside the memory range indicated above.
Which is a big, big surprise.

In my opinion it would be better to spend a few bytes of the memory range 
specified by the user for the mem-struct's.

Regards,
Dag




-----Original Message-----
From: Simon Goldschmidt <INVALID.NOREPLY@gnu.org> 
Sent: Wednesday, September 8, 2021 7:31 PM
To: Simon Goldschmidt <goldsimon@gmx.de>; Dag Midling Larsen 
<DLarsen@shearwatergeo.com>; lwip-devel@nongnu.org; lwip-members@nongnu.org
Subject: [EXTERNAL] [bug #61126] ram_end write outside heap...

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Update of bug #61126 (project lwip):

                  Status:                    None => Invalid                
             Assigned to:                    None => goldsimon              
             Open/Closed:                    Open => Closed                 

    _______________________________________________________

Follow-up Comment #1:

Why do you think so? 'ram_heap' is allocated like this:

uint8_t ram_heap[MEM_SIZE_ALIGNED + (2U * SIZEOF_STRUCT_MEM)];

so writing to a struct mem * which is calculated by 
'ram_heap[MEM_SIZE_ALIGNED]' should surely work, no?

I'll close this as invalid, but you can still respond here if you think 
otherwise. Or if I'm missing something.

    _______________________________________________________

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