On Tue, 25 May 2021 at 04:46, Jisheng Zhang Jisheng.Zhang@synaptics.com wrote:

When we added KFENCE support for arm64, we intended that it would force the entire linear map to be mapped at page granularity, but we only enforced this in arch_add_memory() and not in map_mem(), so memory mapped at boot time can be mapped at a larger granularity.

When booting a kernel with KFENCE=y and RODATA_FULL=n, this results in the following WARNING at boot:

[ 0.000000] ------------[ cut here ]------------ [ 0.000000] WARNING: CPU: 0 PID: 0 at mm/memory.c:2462 apply_to_pmd_range+0xec/0x190 [ 0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.13.0-rc1+ #10 [ 0.000000] Hardware name: linux,dummy-virt (DT) [ 0.000000] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO BTYPE=--) [ 0.000000] pc : apply_to_pmd_range+0xec/0x190 [ 0.000000] lr : __apply_to_page_range+0x94/0x170 [ 0.000000] sp : ffffffc010573e20 [ 0.000000] x29: ffffffc010573e20 x28: ffffff801f400000 x27: ffffff801f401000 [ 0.000000] x26: 0000000000000001 x25: ffffff801f400fff x24: ffffffc010573f28 [ 0.000000] x23: ffffffc01002b710 x22: ffffffc0105fa450 x21: ffffffc010573ee4 [ 0.000000] x20: ffffff801fffb7d0 x19: ffffff801f401000 x18: 00000000fffffffe [ 0.000000] x17: 000000000000003f x16: 000000000000000a x15: ffffffc01060b940 [ 0.000000] x14: 0000000000000000 x13: 0098968000000000 x12: 0000000098968000 [ 0.000000] x11: 0000000000000000 x10: 0000000098968000 x9 : 0000000000000001 [ 0.000000] x8 : 0000000000000000 x7 : ffffffc010573ee4 x6 : 0000000000000001 [ 0.000000] x5 : ffffffc010573f28 x4 : ffffffc01002b710 x3 : 0000000040000000 [ 0.000000] x2 : ffffff801f5fffff x1 : 0000000000000001 x0 : 007800005f400705 [ 0.000000] Call trace: [ 0.000000] apply_to_pmd_range+0xec/0x190 [ 0.000000] __apply_to_page_range+0x94/0x170 [ 0.000000] apply_to_page_range+0x10/0x20 [ 0.000000] __change_memory_common+0x50/0xdc [ 0.000000] set_memory_valid+0x30/0x40 [ 0.000000] kfence_init_pool+0x9c/0x16c [ 0.000000] kfence_init+0x20/0x98 [ 0.000000] start_kernel+0x284/0x3f8

Fixes: 840b23986344 ("arm64, kfence: enable KFENCE for ARM64") Cc: stable@vger.kernel.org # 5.12.x Signed-off-by: Jisheng Zhang Jisheng.Zhang@synaptics.com Acked-by: Mark Rutland mark.rutland@arm.com Acked-by: Marco Elver elver@google.com

Tested-by: Marco Elver elver@google.com

Thank you.

---

Since v1:

• improve commit msg as Mark suggested
• add "Cc: stable@vger.kernel.org"
• collect Mark and Marco's Acks

arch/arm64/mm/mmu.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 6dd9369e3ea0..89b66ef43a0f 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -515,7 +515,8 @@ static void __init map_mem(pgd_t *pgdp) */ BUILD_BUG_ON(pgd_index(direct_map_end - 1) == pgd_index(direct_map_end));

•   if (rodata_full || crash_mem_map || debug_pagealloc_enabled())
  

•   if (rodata_full || crash_mem_map || debug_pagealloc_enabled() ||
  

•       IS_ENABLED(CONFIG_KFENCE))
            flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
  
    /*
  

-- 2.31.0