linux-kernel - [PATCH] powerpc: don't select KFENCE on platform PPC_FSL

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Message-ID: <20210924063927.1341241-1-liushixin2@huawei.com>
Date:   Fri, 24 Sep 2021 14:39:27 +0800
From:   Liu Shixin <liushixin2@...wei.com>
To:     Marco Elver <elver@...gle.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
CC:     <linuxppc-dev@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>,
        "Liu Shixin" <liushixin2@...wei.com>
Subject: [PATCH] powerpc: don't select KFENCE on platform PPC_FSL_BOOK3E

On platform PPC_FSL_BOOK3E, all lowmem is managed by tlbcam. That means
we didn't really map the kfence pool with page granularity. Therefore,
if KFENCE is enabled, the system will hit the following panic:

    BUG: Kernel NULL pointer dereference on read at 0x00000000
    Faulting instruction address: 0xc01de598
    Oops: Kernel access of bad area, sig: 11 [#1]
    BE PAGE_SIZE=4K SMP NR_CPUS=4 MPC8544 DS
    Dumping ftrace buffer:
       (ftrace buffer empty)
    Modules linked in:
    CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.12.0-rc3+ #298
    NIP:  c01de598 LR: c08ae9c4 CTR: 00000000
    REGS: c0b4bea0 TRAP: 0300   Not tainted  (5.12.0-rc3+)
    MSR:  00021000 <CE,ME>  CR: 24000228  XER: 20000000
    DEAR: 00000000 ESR: 00000000
    GPR00: c08ae9c4 c0b4bf60 c0ad64e0 ef720000 00021000 00000000 00000000 00000200
    GPR08: c0ad5000 00000000 00000000 00000004 00000000 008fbb30 00000000 00000000
    GPR16: 00000000 00000000 00000000 00000000 c0000000 00000000 00000000 00000000
    GPR24: c08ca004 c08ca004 c0b6a0e0 c0b60000 c0b58f00 c0850000 c08ca000 ef720000
    NIP [c01de598] kfence_protect+0x44/0x6c
    LR [c08ae9c4] kfence_init+0xfc/0x2a4
    Call Trace:
    [c0b4bf60] [efffe160] 0xefffe160 (unreliable)
    [c0b4bf70] [c08ae9c4] kfence_init+0xfc/0x2a4
    [c0b4bfb0] [c0894d3c] start_kernel+0x3bc/0x574
    [c0b4bff0] [c0000470] set_ivor+0x14c/0x188
    Instruction dump:
    7c0802a6 8109d594 546a653a 90010014 54630026 39200000 7d48502e 2c0a0000
    41820010 554a0026 5469b53a 7d295214 <81490000> 38831000 554a003c 91490000
    random: get_random_bytes called from print_oops_end_marker+0x40/0x78 with crng_init=0
    ---[ end trace 0000000000000000 ]---

Signed-off-by: Liu Shixin <liushixin2@...wei.com>
---
 arch/powerpc/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index d46db0bfb998..cffd57bcb5e4 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -185,7 +185,7 @@ config PPC
 	select HAVE_ARCH_KASAN			if PPC32 && PPC_PAGE_SHIFT <= 14
 	select HAVE_ARCH_KASAN_VMALLOC		if PPC32 && PPC_PAGE_SHIFT <= 14
 	select HAVE_ARCH_KGDB
-	select HAVE_ARCH_KFENCE			if PPC32
+	select HAVE_ARCH_KFENCE			if PPC32 && !PPC_FSL_BOOK3E
 	select HAVE_ARCH_MMAP_RND_BITS
 	select HAVE_ARCH_MMAP_RND_COMPAT_BITS	if COMPAT
 	select HAVE_ARCH_NVRAM_OPS
-- 
2.18.0.huawei.25