This is a note to let you know that I've just added the patch titled
s390/runtime instrumention: fix possible memory corruption
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
s390-runtime-instrumention-fix-possible-memory-corruption.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From d6e646ad7cfa7034d280459b2b2546288f247144 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Date: Mon, 11 Sep 2017 11:24:22 +0200
Subject: s390/runtime instrumention: fix possible memory corruption
From: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/s390/kernel/runtime_instr.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/s390/kernel/runtime_instr.c
+++ b/arch/s390/kernel/runtime_instr.c
@@ -47,11 +47,13 @@ void exit_thread_runtime_instr(void)
{
struct task_struct *task = current;
+ preempt_disable();
if (!task->thread.ri_cb)
return;
disable_runtime_instr();
kfree(task->thread.ri_cb);
task->thread.ri_cb = NULL;
+ preempt_enable();
}
SYSCALL_DEFINE1(s390_runtime_instr, int, command)
@@ -62,9 +64,7 @@ SYSCALL_DEFINE1(s390_runtime_instr, int,
return -EOPNOTSUPP;
if (command == S390_RUNTIME_INSTR_STOP) {
- preempt_disable();
exit_thread_runtime_instr();
- preempt_enable();
return 0;
}
Patches currently in stable-queue which might be from heiko.carstens@xxxxxxxxxx are
queue-4.4/s390-disassembler-add-missing-end-marker-for-e7-table.patch
queue-4.4/s390-fix-transactional-execution-control-register-handling.patch
queue-4.4/s390-runtime-instrumention-fix-possible-memory-corruption.patch