[34-longterm 144/179] proc: restrict access to /proc/PID/io

From: Paul Gortmaker
Date: Mon May 14 2012 - 22:34:56 EST

From: Vasiliy Kulikov <segoon@xxxxxxxxxxxx>

This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.

commit 1d1221f375c94ef961ba8574ac4f85c8870ddd51 upstream.

/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@xxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
fs/proc/base.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 268f00d..08741b0 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2518,6 +2518,9 @@ 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;

@@ -2640,7 +2643,7 @@ static const struct pid_entry tgid_base_stuff[] = {
REG("coredump_filter", S_IRUGO|S_IWUSR, proc_coredump_filter_operations),
- INF("io", S_IRUGO, proc_tgid_io_accounting),
+ INF("io", S_IRUSR, proc_tgid_io_accounting),

@@ -2976,7 +2979,7 @@ static const struct pid_entry tid_base_stuff[] = {
REG("make-it-fail", S_IRUGO|S_IWUSR, proc_fault_inject_operations),
- INF("io", S_IRUGO, proc_tid_io_accounting),
+ INF("io", S_IRUSR, proc_tid_io_accounting),


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