Re: [Security] [PATCH] xtensa: prevent arbitrary read in ptrace

[Chris Zankel]

Hi,

I'll try to run a build this weekend and will look if that code builds 
at all.

Thanks,
-Chris


On 7/8/11 11:42 AM, Oleg Nesterov wrote:
> On 07/08, Andrew Morton wrote:
> > On Thu, 07 Jul 2011 20:03:54 -0400
> > Dan Rosenberg<drosenberg@xxxxxxxxxxxxx>  wrote:
> >
> > > Prevent an arbitrary kernel read. Check the user pointer with
> > > access_ok() before copying data in.
> > >
> > > Signed-off-by: Dan Rosenberg<drosenberg@xxxxxxxxxxxxx>
> > > Cc: stable@xxxxxxxxxx
> > > ---
> > >   arch/xtensa/kernel/ptrace.c |    3 +++
> > >   1 files changed, 3 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/arch/xtensa/kernel/ptrace.c b/arch/xtensa/kernel/ptrace.c
> > > index c72c947..ddce75e 100644
> > > --- a/arch/xtensa/kernel/ptrace.c
> > > +++ b/arch/xtensa/kernel/ptrace.c
> > > @@ -147,6 +147,9 @@ int ptrace_setxregs(struct task_struct *child, void __user *uregs)
> > >   	elf_xtregs_t *xtregs = uregs;
> > >   	int ret = 0;
> > >
> > > +	if (!access_ok(VERIFY_READ, uregs, sizeof(elf_xtregs_t)))
> > > +		return -EIO;
> >
> > This should be -EFAULT, methinks?
>
> Also, it seems that ptrace_setxregs/ptrace_getxregs could be static?
>
> The patch looks "obviously correct" but I don't understand this code.
>
> Hmm. We don't read/write the XTENSA_HAVE_COPROCESSORS data, but use
> sizeof(elf_xtregs_t) anyway. This looks a bit strange but I guess
> this doesn't matter.
>
> Oleg.

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