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

[address@hidden]

Am 09.09.2021 um 08:05 schrieb 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.

I'm not sure I understand this. Have you observed memory corruption or
why did you raise this? Just from reading the code?

Regards,
Simon

>
> 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...
>
> CAUTION:  This email originated from outside your organization. Exercise 
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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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