s390/kasan: fix early pgm check handler execution

Currently if early_pgm_check_handler is called it ends up in pgm check
loop. The problem is that early_pgm_check_handler is instrumented by
KASAN but executed without DAT flag enabled which leads to addressing
exception when KASAN checks try to access shadow memory.

Fix that by executing early handlers with DAT flag on under KASAN as
expected.

Reported-and-tested-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c
index cd241ee66eff4feb6d39842ac9972136394e23c1..0782772318580f8bf908112d143ffc631f22e7f1 100644 (file)
--- a/arch/s390/kernel/early.c
+++ b/arch/s390/kernel/early.c
@@ -170,6 +170,8 @@ static noinline __init void setup_lowcore_early(void)
        psw_t psw;
 
        psw.mask = PSW_MASK_BASE | PSW_DEFAULT_KEY | PSW_MASK_EA | PSW_MASK_BA;
+       if (IS_ENABLED(CONFIG_KASAN))
+               psw.mask |= PSW_MASK_DAT;
        psw.addr = (unsigned long) s390_base_ext_handler;
        S390_lowcore.external_new_psw = psw;
        psw.addr = (unsigned long) s390_base_pgm_handler;