[PATCH v2 4/9] procfs: make /proc/*/{stack,syscall} 0400

[Djalal Harouni <tixxdz@opendz.org>]

The /proc/*/{stack,syscall} contain sensitive information and currently
its mode is 0444. Change this to 0400 so the VFS will be able to block
unprivileged processes from getting file descriptors on arbitrary
privileged /proc/*/{stack,syscall} files.

This will also avoid doing extra unnecessary ptrace checks.

Cc: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
---
 fs/proc/base.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 8d21316..54e926a 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2682,7 +2682,7 @@ static const struct pid_entry tgid_base_stuff[] = {
 #endif
 	REG("comm",      S_IRUGO|S_IWUSR, proc_pid_set_comm_operations),
 #ifdef CONFIG_HAVE_ARCH_TRACEHOOK
-	INF("syscall",    S_IRUGO, proc_pid_syscall),
+	INF("syscall",    S_IRUSR, proc_pid_syscall),
 #endif
 	INF("cmdline",    S_IRUGO, proc_pid_cmdline),
 	ONE("stat",       S_IRUGO, proc_tgid_stat),
@@ -2710,7 +2710,7 @@ static const struct pid_entry tgid_base_stuff[] = {
 	INF("wchan",      S_IRUGO, proc_pid_wchan),
 #endif
 #ifdef CONFIG_STACKTRACE
-	ONE("stack",      S_IRUGO, proc_pid_stack),
+	ONE("stack",      S_IRUSR, proc_pid_stack),
 #endif
 #ifdef CONFIG_SCHEDSTATS
 	INF("schedstat",  S_IRUGO, proc_pid_schedstat),
@@ -3018,7 +3018,7 @@ static const struct pid_entry tid_base_stuff[] = {
 #endif
 	REG("comm",      S_IRUGO|S_IWUSR, proc_pid_set_comm_operations),
 #ifdef CONFIG_HAVE_ARCH_TRACEHOOK
-	INF("syscall",   S_IRUGO, proc_pid_syscall),
+	INF("syscall",   S_IRUSR, proc_pid_syscall),
 #endif
 	INF("cmdline",   S_IRUGO, proc_pid_cmdline),
 	ONE("stat",      S_IRUGO, proc_tid_stat),
@@ -3048,7 +3048,7 @@ static const struct pid_entry tid_base_stuff[] = {
 	INF("wchan",     S_IRUGO, proc_pid_wchan),
 #endif
 #ifdef CONFIG_STACKTRACE
-	ONE("stack",      S_IRUGO, proc_pid_stack),
+	ONE("stack",      S_IRUSR, proc_pid_stack),
 #endif
 #ifdef CONFIG_SCHEDSTATS
 	INF("schedstat", S_IRUGO, proc_pid_schedstat),
-- 
1.7.11.7