s390/runtime instrumention: fix possible memory corruption
authorHeiko Carstens <heiko.carstens@de.ibm.com>
Mon, 11 Sep 2017 09:24:22 +0000 (11:24 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 30 Nov 2017 08:40:38 +0000 (08:40 +0000)
commit27576413d9484cd9df933e3e4c802cb0cfb9c915
tree62e6adce80ae1d1dd148426a833433d06af11b93
parent21caac65d29b7d985a7cd1672ad1dd316b227974
s390/runtime instrumention: fix possible memory corruption

commit d6e646ad7cfa7034d280459b2b2546288f247144 upstream.

For PREEMPT enabled kernels the runtime instrumentation (RI) code
contains a possible use-after-free bug. If a task that makes use of RI
exits, it will execute do_exit() while still enabled for preemption.

That function will call exit_thread_runtime_instr() via
exit_thread(). If exit_thread_runtime_instr() gets preempted after the
RI control block of the task has been freed but before the pointer to
it is set to NULL, then save_ri_cb(), called from switch_to(), will
write to already freed memory.

Avoid this and simply disable preemption while freeing the control
block and setting the pointer to NULL.

Fixes: e4b8b3f33fca ("s390: add support for runtime instrumentation")
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
arch/s390/kernel/runtime_instr.c