[hardy CVE 1/1] proc: restrict access to /proc/PID/io

[Andy Whitcroft]

From: Vasiliy Kulikov <segoon at openwall.com>

/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 at openwall.com>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>

(backported from commit 1d1221f375c94ef961ba8574ac4f85c8870ddd51)
CVE-2011-2495
BugLink: http://bugs.launchpad.net/bugs/866025
Signed-off-by: Andy Whitcroft <apw at canonical.com>
---
 fs/proc/base.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index a68a4ba..7b9485b 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2256,6 +2256,9 @@ static int proc_base_fill_cache(struct file *filp, void *dirent,
 #ifdef CONFIG_TASK_IO_ACCOUNTING
 static int proc_pid_io_accounting(struct task_struct *task, char *buffer)
 {
+	if (!ptrace_may_attach(task))
+		return -EACCES;
+
 	return sprintf(buffer,
 #ifdef CONFIG_TASK_XACCT
 			"rchar: %llu\n"
@@ -2342,7 +2345,7 @@ static const struct pid_entry tgid_base_stuff[] = {
 	REG("coredump_filter", S_IRUGO|S_IWUSR, coredump_filter),
 #endif
 #ifdef CONFIG_TASK_IO_ACCOUNTING
-	INF("io",	S_IRUGO, pid_io_accounting),
+	INF("io",	S_IRUSR, pid_io_accounting),
 #endif
 };
 
-- 
1.7.4.1