linux-kernel - [PATCH 5.18 056/181] KVM: arm64: Prevent kmemleak from accessing pKVM memory

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Message-Id: <20220627111946.191359304@linuxfoundation.org>
Date:   Mon, 27 Jun 2022 13:20:29 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Mike Rapoport <rppt@...nel.org>,
        Quentin Perret <qperret@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.18 056/181] KVM: arm64: Prevent kmemleak from accessing pKVM memory

From: Quentin Perret <qperret@...gle.com>

[ Upstream commit 56961c6331463cce2d84d0f973177a517fb33a82 ]

Commit a7259df76702 ("memblock: make memblock_find_in_range method
private") changed the API using which memory is reserved for the pKVM
hypervisor. However, memblock_phys_alloc() differs from the original API in
terms of kmemleak semantics -- the old one didn't report the reserved
regions to kmemleak while the new one does. Unfortunately, when protected
KVM is enabled, all kernel accesses to pKVM-private memory result in a
fatal exception, which can now happen because of kmemleak scans:

$ echo scan > /sys/kernel/debug/kmemleak
[   34.991354] kvm [304]: nVHE hyp BUG at: [<ffff800008fa3750>] __kvm_nvhe_handle_host_mem_abort+0x270/0x290!
[   34.991580] kvm [304]: Hyp Offset: 0xfffe8be807e00000
[   34.991813] Kernel panic - not syncing: HYP panic:
[   34.991813] PS:600003c9 PC:0000f418011a3750 ESR:00000000f2000800
[   34.991813] FAR:ffff000439200000 HPFAR:0000000004792000 PAR:0000000000000000
[   34.991813] VCPU:0000000000000000
[   34.993660] CPU: 0 PID: 304 Comm: bash Not tainted 5.19.0-rc2 #102
[   34.994059] Hardware name: linux,dummy-virt (DT)
[   34.994452] Call trace:
[   34.994641]  dump_backtrace.part.0+0xcc/0xe0
[   34.994932]  show_stack+0x18/0x6c
[   34.995094]  dump_stack_lvl+0x68/0x84
[   34.995276]  dump_stack+0x18/0x34
[   34.995484]  panic+0x16c/0x354
[   34.995673]  __hyp_pgtable_total_pages+0x0/0x60
[   34.995933]  scan_block+0x74/0x12c
[   34.996129]  scan_gray_list+0xd8/0x19c
[   34.996332]  kmemleak_scan+0x2c8/0x580
[   34.996535]  kmemleak_write+0x340/0x4a0
[   34.996744]  full_proxy_write+0x60/0xbc
[   34.996967]  vfs_write+0xc4/0x2b0
[   34.997136]  ksys_write+0x68/0xf4
[   34.997311]  __arm64_sys_write+0x20/0x2c
[   34.997532]  invoke_syscall+0x48/0x114
[   34.997779]  el0_svc_common.constprop.0+0x44/0xec
[   34.998029]  do_el0_svc+0x2c/0xc0
[   34.998205]  el0_svc+0x2c/0x84
[   34.998421]  el0t_64_sync_handler+0xf4/0x100
[   34.998653]  el0t_64_sync+0x18c/0x190
[   34.999252] SMP: stopping secondary CPUs
[   35.000034] Kernel Offset: disabled
[   35.000261] CPU features: 0x800,00007831,00001086
[   35.000642] Memory Limit: none
[   35.001329] ---[ end Kernel panic - not syncing: HYP panic:
[   35.001329] PS:600003c9 PC:0000f418011a3750 ESR:00000000f2000800
[   35.001329] FAR:ffff000439200000 HPFAR:0000000004792000 PAR:0000000000000000
[   35.001329] VCPU:0000000000000000 ]---

Fix this by explicitly excluding the hypervisor's memory pool from
kmemleak like we already do for the hyp BSS.

Cc: Mike Rapoport <rppt@...nel.org>
Fixes: a7259df76702 ("memblock: make memblock_find_in_range method private")
Signed-off-by: Quentin Perret <qperret@...gle.com>
Acked-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Marc Zyngier <maz@...nel.org>
Link: https://lore.kernel.org/r/20220616161135.3997786-1-qperret@google.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/arm64/kvm/arm.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index a66d83540c15..f88919a793ad 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -2011,11 +2011,11 @@ static int finalize_hyp_mode(void)
 		return 0;
 
 	/*
-	 * Exclude HYP BSS from kmemleak so that it doesn't get peeked
-	 * at, which would end badly once the section is inaccessible.
-	 * None of other sections should ever be introspected.
+	 * Exclude HYP sections from kmemleak so that they don't get peeked
+	 * at, which would end badly once inaccessible.
 	 */
 	kmemleak_free_part(__hyp_bss_start, __hyp_bss_end - __hyp_bss_start);
+	kmemleak_free_part(__va(hyp_mem_base), hyp_mem_size);
 	return pkvm_drop_host_privileges();
 }
 
-- 
2.35.1