linux-kernel - vm: weird behaviour when munmapping

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 17 Nov 2006 11:31:24 +0000 (GMT)
From:	moreau francis <francis_moreau2000@...oo.fr>
To:	linux-kernel@...r.kernel.org
Subject: vm: weird behaviour when munmapping

Hmm, I'm probably missing something but I don't see what. Please be
nice even if the question is really stupid ;)

I'm looking at mmap.c code and to understand it I decided to implement
a dumb char device that implement its own foo_mmap() method. In this
method it defined its own vma ops:

    static void foo_vma_open(struct vm_area_struct *vma)
    static void foo_vma_close(struct vm_area_struct *vma)

A dumb application mmap the device in order to make foo_mmap() install
the vma ops.

    mmap(NULL, 16384, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);

mmap returned 0x2aaae000 for example. Until now, foo_vma_open() and
foo_vma_close() are not called.

Now I want to unmap the first part of the previous mapping to see how
vma ops are called. So I did:

    munmap(0x2aaae000, 1024);

and here's what happen:

    foo_vma_open(vma) is called with:
        vma->vm_start = 0x2aaae000
        vma->vm_end = 0x2aaaf000

    foo_vma_close(vma) is called with:
        vma->vm_start = 0x2aaae000
        vma->vm_end = 0x2aaaf000

However I would have expected:

    foo_vma_open(vma) is called with:
        vma->vm_start = 0x2aaaf000
        vma->vm_end = 0x2aaab2000

    foo_vma_close(vma) is called with:
        vma->vm_start = 0x2aaae000
        vma->vm_end = 0x2aaaf000

Can anybody tell me why I get this behaviour ?

thanks

Francis

___________________________________________________________________________ 
Découvrez une nouvelle façon d'obtenir des réponses à toutes vos questions ! 
Profitez des connaissances, des opinions et des expériences des internautes sur Yahoo! Questions/Réponses 
http://fr.answers.yahoo.com
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/