[PATCH 5.15 046/135] KVM: arm64: Prevent kmemleak from accessing pKVM memory

Greg Kroah-Hartman
2022-06-27T11:39:09Z

From: Quentin Perret <qperret@google.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@kernel.org>
Fixes: a7259df76702 ("memblock: make memblock_find_in_range method private")
Signed-off-by: Quentin Perret <qperret@google.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220616161135.3997786-1-qperret@google.com
Signed-off-by: Sasha Levin <sashal@kernel.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 a30c036577a3..f181527f9d43 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