Re: Regression in 2.6.25-rc3: s2ram segfaults before suspending

Pavel Machek
2008-03-03T14:45:41Z

Hi!

> > > Klaus S. Madsen wrote:
> > >> open("/dev/mem", O_RDWR) = 5
> > >> mmap2(NULL, 1282, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_SHARED|MAP_FIXED, 5, 0) = 0
> > >> mmap2(0xa0000, 393216, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_FIXED, 5, 0xa0) = 0xa0000
> > > ^^^^^^^^^^^^^^^^^^^^
> > >> close(5) = 0
> > >> ioperm(0, 0x400, 0x1) = 0
> > >> iopl(0x3) = 0
> > >> access("/sys/bus/pci", R_OK) = 0
> > >> write(1, "Calling get_mode\n", 17) = 17
> > >> vm86(0x1, 0xb7f14ccc, 0xb7f14830, 0xc000, 0x18b6 <unfinished ...>
> > >> --- SIGSEGV (Segmentation fault) @ 0 (0) ---
> > >> +++ killed by SIGSEGV (core dumped) +++
> > >
> > > This is the VGA BIOS being mapped, it's mapped PROT_READ|PROT_WRITE, but
> > > no PROT_EXEC; if the kernel is NX-capable it *should* segfault trying to
> > > execute out of this area, which is exactly what will happen when vm86
> > > executes INT 10h.
> > >
> > > If we can find that mmap() in the s2ram source code and add PROT_EXEC
> > > to it, it would be interesting.
> >
> > Klaus, could you send your .config as well? Lets make sure that NX is
> > even relevant in this context.
> Allright. The mmap in question is in the x86-common.c file in libx86,
> and adding PROT_EXEC to it solves the problem.

Ok, sw should probably fix that in s2ram... can you mail a patch to
me, and suspend-devel?

> I have attached my .config.
>
> The only thing I don't understand is why this is suddenly a problem with
> 2.6.25, and not with 2.6.24? Is there a bug in 2.6.24 and previously
> that allows real-mode execution of non-executable pages?

It is strange indeed... Should it be traced as an regression?
Pavel
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