linux-kernel - [PATCH 1/2] proc: restrict access to /proc/PID/io

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Message-Id: <1308917318-4749-1-git-send-email-segoon@openwall.com>
Date:	Fri, 24 Jun 2011 16:08:38 +0400
From:	Vasiliy Kulikov <segoon@...nwall.com>
To:	linux-kernel@...r.kernel.org
Cc:	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	David Rientjes <rientjes@...gle.com>,
	Stephen Wilson <wilsons@...rt.ca>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	security@...nel.org, Eric Paris <eparis@...hat.com>,
	Solar Designer <solar@...nwall.com>
Subject: [PATCH 1/2] proc: restrict access to /proc/PID/io

/proc/PID/io may be used for gathering private information.  E.g. for
openssh and vsftpd daemons wchars/rchars may be used to learn the
precise password length.  Restrict it to processes being able to ptrace
the target process.

ptrace_may_access() is needed to prevent keeping open file descriptor of
"io" file, executing setuid binary and gathering io information of the
setuid'ed process.

Signed-off-by: Vasiliy Kulikov <segoon@...nwall.com>
---
 fs/proc/base.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 14def99..5ae25d1 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2712,6 +2712,9 @@ static int do_io_accounting(struct task_struct *task, char *buffer, int whole)
 	struct task_io_accounting acct = task->ioac;
 	unsigned long flags;
 
+	if (!ptrace_may_access(task, PTRACE_MODE_READ))
+		return -EACCES;
+
 	if (whole && lock_task_sighand(task, &flags)) {
 		struct task_struct *t = task;
 
@@ -2843,7 +2846,7 @@ static const struct pid_entry tgid_base_stuff[] = {
 	REG("coredump_filter", S_IRUGO|S_IWUSR, proc_coredump_filter_operations),
 #endif
 #ifdef CONFIG_TASK_IO_ACCOUNTING
-	INF("io",	S_IRUGO, proc_tgid_io_accounting),
+	INF("io",	S_IRUSR, proc_tgid_io_accounting),
 #endif
 #ifdef CONFIG_HARDWALL
 	INF("hardwall",   S_IRUGO, proc_pid_hardwall),
@@ -3185,7 +3188,7 @@ static const struct pid_entry tid_base_stuff[] = {
 	REG("make-it-fail", S_IRUGO|S_IWUSR, proc_fault_inject_operations),
 #endif
 #ifdef CONFIG_TASK_IO_ACCOUNTING
-	INF("io",	S_IRUGO, proc_tid_io_accounting),
+	INF("io",	S_IRUSR, proc_tid_io_accounting),
 #endif
 #ifdef CONFIG_HARDWALL
 	INF("hardwall",   S_IRUGO, proc_pid_hardwall),
-- 
1.7.0.4

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