New subject: [Bug 574654] qemu fails with "mmap: permission denied"

28 Jan 2010

      http://bugzilla.novell.com/show_bug.cgi?id=574654

http://bugzilla.novell.com/show_bug.cgi?id=574654#c0

           Summary: qemu fails with "mmap: permission denied"
    Classification: openSUSE
           Product: openSUSE 11.2
           Version: Final
          Platform: i686
        OS/Version: openSUSE 11.2
            Status: NEW
          Severity: Normal
          Priority: P5 - None
         Component: Kernel
        AssignedTo: kernel-maintainers@forge.provo.novell.com
        ReportedBy: wolfgang@rosenauer.org
         QAContact: qa@suse.de
          Found By: ---
           Blocker: ---

(This is default openSUSE 11.2 with latest update kernel)

I'm using a scratchbox environment with an ARM target using qemu.
When I try to compile a bigger project (mozilla: it runs its own JS interpreter
during build) it fails because of that qemu issue.

Searching for issues on the net revealed that qemu should be run with
mmap_min_addr set to 4096. openSUSE sets 65536 as CONFIG_DEFAULT_MMAP_MIN_ADDR.
So one would expect that it can be fixed by setting the mmap_min_addr sysctl
and apparently it also gets used (the value in sysctl changes as expected).
The error just doesn't go away though.

So I've recompiled the kernel with 
CONFIG_DEFAULT_MMAP_MIN_ADDR=4096
CONFIG_LSM_MMAP_MIN_ADDR=4096
and with that kernel everything is working fine.

Disclaimer: I don't have much experience in kernel hacking but I've tried to
follow the code but fail to see why that happens.
I found:
dac_mmap_min_addr - is the default value and this can be changed by sysctl
mmap_min_addr - is the maximum of dac_mmap_min_addr and
CONFIG_LSM_MMAP_MIN_ADDR

cap_file_mmap() is comparing against dac_mmap_min_addr and therefore shouldn't
be the issue as setting sysctl didn't work.

apparmor_file_mmap() checks against mmap_min_addr but I don't run apparmor
actively on these processes.

selinux_file_mmap() checks against CONFIG_LSM_MMAP_MIN_ADDR but I don't do
anything with selinux

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[Bug 574654] New: qemu fails with "mmap: permission denied"

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