From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Howells Date: Mon, 24 May 2010 14:36:57 +0000 Subject: Re: [PATCH -mm 1/1] ptrace: PTRACE_GETFDPIC: fix the unsafe usage of child->mm Message-Id: <25539.1274711817@redhat.com> List-Id: References: <20100522165401.GB19573@redhat.com> <1266280229-18469-1-git-send-email-vapier@gentoo.org> <1274431345-22366-1-git-send-email-vapier@gentoo.org> <20100521162659.GA16193@redhat.com> <20100521183512.4477F40476@magilla.sf.frob.com> <20100522165320.GA19573@redhat.com> In-Reply-To: <20100522165401.GB19573@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Oleg Nesterov Cc: dhowells@redhat.com, Roland McGrath , Andrew Morton , Mike Frysinger , linux-sh@vger.kernel.org, Paul Mundt , uclinux-dist-devel@blackfin.uclinux.org, linux-kernel@vger.kernel.org Oleg Nesterov wrote: > Now that Mike Frysinger unified the FDPIC ptrace code, we can fix > the unsafe usage of child->mm in ptrace_request(PTRACE_GETFDPIC). > > We have the reference to task_struct, and ptrace_check_attach() > verified the tracee is stopped. But nothing can protect from > SIGKILL after that, we must not assume child->mm != NULL. > > Signed-off-by: Oleg Nesterov Acked-by: David Howells Does it make sense to move the call to get_task_mm() up to sys_ptrace() since several ptrace functions use it? The mm pointer could then be handed down the ptrace hierarchy. David