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| author | Heiko Carstens <heiko.carstens@de.ibm.com> | 2017-09-11 12:24:22 +0300 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2017-09-28 08:29:39 +0300 |
| commit | fa1edf3f63c05ca8eacafcd7048ed91e5360f1a8 (patch) | |
| tree | dbbc2aeb26cff7505785b136cc947f7a2b2eb529 /arch/s390/kernel/guarded_storage.c | |
| parent | 8d9047f8b967ce6181fd824ae922978e1b055cc0 (diff) | |
| download | linux-fa1edf3f63c05ca8eacafcd7048ed91e5360f1a8.tar.xz | |
s390/guarded storage: fix possible memory corruption
For PREEMPT enabled kernels the guarded storage (GS) code contains a
possible use-after-free bug. If a task that makes use of GS 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_gs() gets preempted after the GS control block of the
task has been freed but before the pointer to it is set to NULL, then
save_gs_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: 916cda1aa1b4 ("s390: add a system call for guarded storage")
Cc: <stable@vger.kernel.org> # v4.12+
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>
Diffstat (limited to 'arch/s390/kernel/guarded_storage.c')
| -rw-r--r-- | arch/s390/kernel/guarded_storage.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/s390/kernel/guarded_storage.c b/arch/s390/kernel/guarded_storage.c index 6f064745c3b1..4920cf6ffa00 100644 --- a/arch/s390/kernel/guarded_storage.c +++ b/arch/s390/kernel/guarded_storage.c @@ -13,9 +13,11 @@ void exit_thread_gs(void) { + preempt_disable(); kfree(current->thread.gs_cb); kfree(current->thread.gs_bc_cb); current->thread.gs_cb = current->thread.gs_bc_cb = NULL; + preempt_enable(); } static int gs_enable(void) |