forked from rubenslte/android_kernel_samsung_msm8226
Jann Horn
31ccd3538f
commit 54ffccbf053b5b6ca4f6e45094b942fab92a25fc upstream.
tiocspgrp() takes two tty_struct pointers: One to the tty that userspace
passed to ioctl() (`tty`) and one to the TTY being changed (`real_tty`).
These pointers are different when ioctl() is called with a master fd.
To properly lock real_tty->pgrp, we must take real_tty->ctrl_lock.
This bug makes it possible for racing ioctl(TIOCSPGRP, ...) calls on
both sides of a PTY pair to corrupt the refcount of `struct pid`,
leading to use-after-free errors.
Fixes: 47f86834bb ("redo locking of tty->pgrp")
CC: stable@kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Change-Id: Ib41dbafa06012374b219c7236968733373189ffd
CVE-2020-29661
Signed-off-by: Kevin F. Haggerty <haggertk@lineageos.org>