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Commit 31367466 authored by Otto Ebeling's avatar Otto Ebeling Committed by Linus Torvalds
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Unify migrate_pages and move_pages access checks 

Commit 197e7e52 ("Sanitize 'move_pages()' permission checks") fixed
a security issue I reported in the move_pages syscall, and made it so
that you can't act on set-uid processes unless you have the
CAP_SYS_PTRACE capability.

Unify the access check logic of migrate_pages to match the new behavior
of move_pages.  We discussed this a bit in the security@ list and
thought it'd be good for consistency even though there's no evident
security impact.  The NUMA node access checks are left intact and
require CAP_SYS_NICE as before.

Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1710011830320.6333@lakka.kapsi.fi


Signed-off-by: default avatarOtto Ebeling <otto.ebeling@iki.fi>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7f0b5fb9

mm/mempolicy.c

+4 −9
Original line number Diff line number Diff line
@@ -85,6 +85,7 @@ 
#include <linux/interrupt.h>

#include <linux/init.h>

#include <linux/compat.h>

#include <linux/ptrace.h>

#include <linux/swap.h>

#include <linux/seq_file.h>

#include <linux/proc_fs.h>
@@ -1365,7 +1366,6 @@ SYSCALL_DEFINE4(migrate_pages, pid_t, pid, unsigned long, maxnode, 
		const unsigned long __user *, old_nodes,

		const unsigned long __user *, new_nodes)

{

	const struct cred *cred = current_cred(), *tcred;

	struct mm_struct *mm = NULL;

	struct task_struct *task;

	nodemask_t task_nodes;
@@ -1401,15 +1401,10 @@ SYSCALL_DEFINE4(migrate_pages, pid_t, pid, unsigned long, maxnode, 
	err = -EINVAL;



	/*

	 * Check if this process has the right to modify the specified

	 * process. The right exists if the process has administrative

	 * capabilities, superuser privileges or the same

	 * userid as the target process.

	 */

	tcred = __task_cred(task);

	if (!uid_eq(cred->euid, tcred->suid) && !uid_eq(cred->euid, tcred->uid) &&

	    !uid_eq(cred->uid,  tcred->suid) && !uid_eq(cred->uid,  tcred->uid) &&

	    !capable(CAP_SYS_NICE)) {

	 * Check if this process has the right to modify the specified process.

	 * Use the regular "ptrace_may_access()" checks.

	 */

	if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {

		rcu_read_unlock();

		err = -EPERM;

		goto out_put;