mmap 0-th page

mmap 0-th page

[michal.hrachovec]

Good afternoon,

I am trying to allocate the 0-th page with mmap function in my code.
I am always getting this error with this error-code: mmap error ffffffff
Then I was searching the internet for this topic and I have found the 
same topic at stackoverflow web pages.

Here I am sending the link:
https://stackoverflow.com/questions/63790813/allocating-address-zero-on-linux-with-mmap-fails

I was setting value of |/proc/sys/vm/mmap_min_add to zero and using the 
root privileges along the link.
And I am having the same problem still.

Can you help, please.

Thank you for the reply.

Michal Hrachovec

|

Re: mmap 0-th page

[Greg KH]

On Fri, Jul 26, 2024 at 12:36:29PM +0200, michal.hrachovec@volny.cz wrote:
> Good afternoon,
> 
> I am trying to allocate the 0-th page with mmap function in my code.
> I am always getting this error with this error-code: mmap error ffffffff
> Then I was searching the internet for this topic and I have found the same
> topic at stackoverflow web pages.
> 
> Here I am sending the link:
> https://stackoverflow.com/questions/63790813/allocating-address-zero-on-linux-with-mmap-fails
> 
> I was setting value of |/proc/sys/vm/mmap_min_add to zero and using the root
> privileges along the link.
> And I am having the same problem still.
> 
> Can you help, please.

The stable and regressions mailing list is not the proper place for
this type of question, sorry.

If this is a regression from a previous kernel version, it might be the
place but you don't specify any kernel version information here.

best of luck!

greg k-h

Re: mmap 0-th page

[Jiri Slaby]

On 26. 07. 24, 12:36, michal.hrachovec@volny.cz wrote:
> I am trying to allocate the 0-th page with mmap function in my code.
> I am always getting this error with this error-code: mmap error ffffffff
> Then I was searching the internet for this topic and I have found the 
> same topic at stackoverflow web pages.


         char *zero = mmap(NULL, 4096, PROT_READ | PROT_WRITE, 
MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
         *(char *)(NULL) = 'A';
         printf("%c\n", *zero);

still yields 'A' here with 6.10.2 w/ vm.mmap_min_addr=0.

-- 
js
suse labs

Re: mmap 0-th page

[Jiri Slaby]

On 31. 07. 24, 9:39, Jiri Slaby wrote:
> On 26. 07. 24, 12:36, michal.hrachovec@volny.cz wrote:
>> I am trying to allocate the 0-th page with mmap function in my code.
>> I am always getting this error with this error-code: mmap error ffffffff
>> Then I was searching the internet for this topic and I have found the 
>> same topic at stackoverflow web pages.
> 
> 
>          char *zero = mmap(NULL, 4096, PROT_READ | PROT_WRITE, 
> MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
>          *(char *)(NULL) = 'A';
>          printf("%c\n", *zero);
> 
> still yields 'A' here with 6.10.2 w/ vm.mmap_min_addr=0.
Yeah and mind LSMs...

-- 
-- 
js
suse labs