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Date:   Tue, 25 May 2021 10:45:51 +0800
From:   Jisheng Zhang <Jisheng.Zhang@synaptics.com>
To:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Marco Elver <elver@google.com>
Cc:     Alexander Potapenko <glider@google.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        stable@vger.kernel.org
Subject: [PATCH v2] arm64: mm: don't use CON and BLK mapping if KFENCE is
 enabled
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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>
---
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