linux/drivers/virt
Mathias Krause f1ce3986ba nitro_enclaves: Fix stale file descriptors on failed usercopy
A failing usercopy of the slot uid will lead to a stale entry in the
file descriptor table as put_unused_fd() won't release it. This enables
userland to refer to a dangling 'file' object through that still valid
file descriptor, leading to all kinds of use-after-free exploitation
scenarios.

Exchanging put_unused_fd() for close_fd(), ksys_close() or alike won't
solve the underlying issue, as the file descriptor might have been
replaced in the meantime, e.g. via userland calling close() on it
(leading to a NULL pointer dereference in the error handling code as
'fget(enclave_fd)' will return a NULL pointer) or by dup2()'ing a
completely different file object to that very file descriptor, leading
to the same situation: a dangling file descriptor pointing to a freed
object -- just in this case to a file object of user's choosing.

Generally speaking, after the call to fd_install() the file descriptor
is live and userland is free to do whatever with it. We cannot rely on
it to still refer to our enclave object afterwards. In fact, by abusing
userfaultfd() userland can hit the condition without any racing and
abuse the error handling in the nitro code as it pleases.

To fix the above issues, defer the call to fd_install() until all
possible errors are handled. In this case it's just the usercopy, so do
it directly in ne_create_vm_ioctl() itself.

Signed-off-by: Mathias Krause <minipli@grsecurity.net>
Signed-off-by: Andra Paraschiv <andraprs@amazon.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20210429165941.27020-2-andraprs@amazon.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-04-29 19:06:49 +02:00
..
acrn virt: acrn: Fix document of acrn_msi_inject() 2021-03-24 08:26:30 +01:00
nitro_enclaves nitro_enclaves: Fix stale file descriptors on failed usercopy 2021-04-29 19:06:49 +02:00
vboxguest virt: vbox: Do not use wait_event_interruptible when called from kernel context 2021-01-27 14:37:02 +01:00
fsl_hypervisor.c drivers/virt/fsl_hypervisor: Fix error handling path 2020-09-07 14:57:31 +02:00
Kconfig virt: acrn: Introduce ACRN HSM basic driver 2021-02-09 10:58:18 +01:00
Makefile virt: acrn: Introduce ACRN HSM basic driver 2021-02-09 10:58:18 +01:00