Commit bfb819ea authored by Kees Cook's avatar Kees Cook Committed by Linus Torvalds
Browse files

proc: Check /proc/$pid/attr/ writes against file opener

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: 1da177e4

 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ad9f25d3
......@@ -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) {
......
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