From: Guenter Roeck linux@roeck-us.net
commit 65d1e3ddeae117f6a224535e10a09145f0f96508 upstream.
Mainline crashes as follows when running nios2 images.
On node 0 totalpages: 65536 free_area_init_node: node 0, pgdat c8408fa0, node_mem_map c8726000 Normal zone: 512 pages used for memmap Normal zone: 0 pages reserved Normal zone: 65536 pages, LIFO batch:15 Unable to handle kernel NULL pointer dereference at virtual address 00000000 ea = c8003cb0, ra = c81cbf40, cause = 15 Kernel panic - not syncing: Oops
Problem is seen because get_cycles() is called before the timer it depends on is initialized. Returning 0 in that situation fixes the problem.
Fixes: 33d72f3822d7 ("init/main.c: extract early boot entropy from the ..") Cc: Laura Abbott labbott@redhat.com Cc: Kees Cook keescook@chromium.org Cc: Daniel Micay danielmicay@gmail.com Signed-off-by: Guenter Roeck linux@roeck-us.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/nios2/kernel/time.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/arch/nios2/kernel/time.c +++ b/arch/nios2/kernel/time.c @@ -107,7 +107,10 @@ static struct nios2_clocksource nios2_cs
cycles_t get_cycles(void) { - return nios2_timer_read(&nios2_cs.cs); + /* Only read timer if it has been initialized */ + if (nios2_cs.timer.base) + return nios2_timer_read(&nios2_cs.cs); + return 0; } EXPORT_SYMBOL(get_cycles);