proc: restrict access to /proc/PID/io

[ upstream commit 1d1221f375c94ef961ba8574ac4f85c8870ddd51 ]

/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.

Said to be CVE-2011-2495

Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index d073b90f5dc6ea3f07f140576988a624b8d95426..c410e23ecd794aad1c63e23dfbe52238d2b477ee 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2514,6 +2514,9 @@ 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;
 
@@ -2636,7 +2639,7 @@ 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
 };
 
@@ -2972,7 +2975,7 @@ 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
 };