From: Heiko Carstens hca@linux.ibm.com
[ Upstream commit fd78c59446b8d050ecf3e0897c5a486c7de7c595 ]
The key member of the runtime instrumentation control block contains only the access key, not the complete storage key. Therefore the value must be shifted by four bits. Since existing user space does not necessarily query and set the access key correctly, just ignore the user space provided key and use the correct one. Note: this is only relevant for debugging purposes in case somebody compiles a kernel with a default storage access key set to a value not equal to zero.
Fixes: 262832bc5acd ("s390/ptrace: add runtime instrumention register get/set") Reported-by: Claudio Imbrenda imbrenda@linux.ibm.com Signed-off-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/kernel/ptrace.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c index 3cc15c0662983..2924f236d89c6 100644 --- a/arch/s390/kernel/ptrace.c +++ b/arch/s390/kernel/ptrace.c @@ -1310,7 +1310,6 @@ static bool is_ri_cb_valid(struct runtime_instr_cb *cb) cb->pc == 1 && cb->qc == 0 && cb->reserved2 == 0 && - cb->key == PAGE_DEFAULT_KEY && cb->reserved3 == 0 && cb->reserved4 == 0 && cb->reserved5 == 0 && @@ -1374,7 +1373,11 @@ static int s390_runtime_instr_set(struct task_struct *target, kfree(data); return -EINVAL; } - + /* + * Override access key in any case, since user space should + * not be able to set it, nor should it care about it. + */ + ri_cb.key = PAGE_DEFAULT_KEY >> 4; preempt_disable(); if (!target->thread.ri_cb) target->thread.ri_cb = data;