procfs: make /proc/*/{stack,syscall,personality} 0400

These procfs files contain sensitive information and currently their
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,personality} files.

This reduces the scope of ASLR leaking and bypasses by protecting already
running processes.

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 6 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index b9760628e1fd..a08c92289357 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2588,7 +2588,7 @@ static const struct pid_entry tgid_base_stuff[] = {
         REG("environ",    S_IRUSR, proc_environ_operations),
         INF("auxv",       S_IRUSR, proc_pid_auxv),
         ONE("status",     S_IRUGO, proc_pid_status),
-        ONE("personality", S_IRUGO, proc_pid_personality),
+        ONE("personality", S_IRUSR, proc_pid_personality),
         INF("limits",     S_IRUGO, proc_pid_limits),
 #ifdef CONFIG_SCHED_DEBUG
         REG("sched",      S_IRUGO|S_IWUSR, proc_pid_sched_operations),
@@ -2598,7 +2598,7 @@ 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),
@@ -2626,7 +2626,7 @@ 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),
@@ -2927,14 +2927,14 @@ static const struct pid_entry tid_base_stuff[] = {
         REG("environ",   S_IRUSR, proc_environ_operations),
         INF("auxv",      S_IRUSR, proc_pid_auxv),
         ONE("status",    S_IRUGO, proc_pid_status),
-        ONE("personality", S_IRUGO, proc_pid_personality),
+        ONE("personality", S_IRUSR, proc_pid_personality),
         INF("limits",    S_IRUGO, proc_pid_limits),
 #ifdef CONFIG_SCHED_DEBUG
         REG("sched",     S_IRUGO|S_IWUSR, proc_pid_sched_operations),
 #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),
@@ -2964,7 +2964,7 @@ 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),