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SubjectRe: [Security] [PATCH] xtensa: prevent arbitrary read in ptrace
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Sorry for the top post and any email mangling (mobile).

I only used EIO to mirror the existing behavior in ptrace_getxregs(). EFAULT seems better.

-Dan

------Original Message------
From: Andrew Morton
To: Dan Rosenberg
Cc: chris@zankel.net
Cc: security@kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Oleg Nesterov
Subject: Re: [Security] [PATCH] xtensa: prevent arbitrary read in ptrace
Sent: Jul 8, 2011 2:27 PM
On Thu, 07 Jul 2011 20:03:54 -0400
Dan Rosenberg <drosenberg@vsecurity.com> wrote:

> Prevent an arbitrary kernel read. Check the user pointer with
> access_ok() before copying data in.
>
> Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
> Cc: stable@kernel.org
> ---
> 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?

> +
> #if XTENSA_HAVE_COPROCESSORS
> /* Flush all coprocessors before we overwrite them. */
> coprocessor_flush_all(ti);
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