linux-kernel - Re: [PATCH -mm 2/4] ptrace: compat_ptrace

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Message-ID: <20080313144221.GA10328@c2.user-mode-linux.org>
Date:	Thu, 13 Mar 2008 10:42:21 -0400
From:	Jeff Dike <jdike@...toit.com>
To:	Roland McGrath <roland@...hat.com>
Cc:	Paul Mackerras <paulus@...ba.org>,
	Anton Blanchard <anton@...ba.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -mm 2/4] ptrace: compat_ptrace_request siginfo

On Thu, Mar 13, 2008 at 01:32:43AM -0700, Roland McGrath wrote:
> On powerpc, this fixes a longstanding regression of 32-bit ptrace
> calls on 64-bit kernels vs native calls (64-bit calls or 32-bit
> kernels).  This can be seen in a 32-bit call using PTRACE_GETSIGINFO
> to examine e.g. siginfo_t.si_addr from a signal that sets it.
> (This was broken as of 2.6.24 and, I presume, many or all prior versions.)

BTW, this also fixes a long-standing bug in x86_64 ptrace32_siginfo:

	ret = sys_ptrace(request, pid, addr, (unsigned long)si);
	if (ret)
		return ret;
	if (request == PTRACE_GETSIGINFO) {
		if (copy_from_user(&ssi, si, sizeof(siginfo_t)))
			return -EFAULT;
		ret = copy_siginfo_to_user32(si32, &ssi);
	}

si comes back with the upper bits of si_code missing, courtesy of
copy_siginfo_to_user:

	err |= __put_user((short)from->si_code, &to->si_code);

causing copy_siginfo_to_user32 to not copy any fields of the union
past the first word because the upper 16 bits are used to figure out
what needs copying.

			Jeff

-- 
Work email - jdike at linux dot intel dot com
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