lkml.org 
[lkml]   [2021]   [May]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] proc: Check /proc/$pid/attr/ writes against file opener
Date
Fix another "confused deputy" weakness[1]. Writes to /proc/$pid/attr/
files need to check the opener credentials, since these fds do not
transition state across execve(). Without this, it is possible to
trick another process (which may have different credentials) to write
to its own /proc/$pid/attr/ files, leading to unexpected and possibly
exploitable behaviors.

[1] https://www.kernel.org/doc/html/latest/security/credentials.html?highlight=confused#open-file-credentials

Fixes: 1da177e4c3f41 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
fs/proc/base.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 3851bfcdba56..58bbf334265b 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2703,6 +2703,10 @@ static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf,
void *page;
int rv;

+ /* A task may only write when it was the opener. */
+ if (file->f_cred != current_real_cred())
+ return -EPERM;
+
rcu_read_lock();
task = pid_task(proc_pid(inode), PIDTYPE_PID);
if (!task) {
--
2.25.1
\
 
 \ /
  Last update: 2021-05-25 21:38    [W:0.065 / U:0.992 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site