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

[Vasiliy Kulikov]

/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>
---
 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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