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authorSean Christopherson <seanjc@google.com>2022-11-10 20:35:04 +0000
committerDave Hansen <dave.hansen@linux.intel.com>2022-12-15 10:37:28 -0800
commit1cfaac2400c73378e78182a706be0f3ac8b93cd7 (patch)
tree98558786798454889875b45910a36eedef8c4666 /arch
parentbde258d97409f2a45243cb393a55ea9ecfc7aba5 (diff)
x86/kasan: Populate shadow for shared chunk of the CPU entry area
Popuplate the shadow for the shared portion of the CPU entry area, i.e. the read-only IDT mapping, during KASAN initialization. A recent change modified KASAN to map the per-CPU areas on-demand, but forgot to keep a shadow for the common area that is shared amongst all CPUs. Map the common area in KASAN init instead of letting idt_map_in_cea() do the dirty work so that it Just Works in the unlikely event more shared data is shoved into the CPU entry area. The bug manifests as a not-present #PF when software attempts to lookup an IDT entry, e.g. when KVM is handling IRQs on Intel CPUs (KVM performs direct CALL to the IRQ handler to avoid the overhead of INTn): BUG: unable to handle page fault for address: fffffbc0000001d8 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 16c03a067 P4D 16c03a067 PUD 0 Oops: 0000 [#1] PREEMPT SMP KASAN CPU: 5 PID: 901 Comm: repro Tainted: G W 6.1.0-rc3+ #410 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:kasan_check_range+0xdf/0x190 vmx_handle_exit_irqoff+0x152/0x290 [kvm_intel] vcpu_run+0x1d89/0x2bd0 [kvm] kvm_arch_vcpu_ioctl_run+0x3ce/0xa70 [kvm] kvm_vcpu_ioctl+0x349/0x900 [kvm] __x64_sys_ioctl+0xb8/0xf0 do_syscall_64+0x2b/0x50 entry_SYSCALL_64_after_hwframe+0x46/0xb0 Fixes: 9fd429c28073 ("x86/kasan: Map shadow for percpu pages on demand") Reported-by: syzbot+8cdd16fd5a6c0565e227@syzkaller.appspotmail.com Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20221110203504.1985010-6-seanjc@google.com
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/mm/kasan_init_64.c12
1 files changed, 11 insertions, 1 deletions
diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
index afc5e129ca7b..0302491d799d 100644
--- a/arch/x86/mm/kasan_init_64.c
+++ b/arch/x86/mm/kasan_init_64.c
@@ -341,7 +341,7 @@ void __init kasan_populate_shadow_for_vaddr(void *va, size_t size, int nid)
void __init kasan_init(void)
{
- unsigned long shadow_cea_begin, shadow_cea_end;
+ unsigned long shadow_cea_begin, shadow_cea_per_cpu_begin, shadow_cea_end;
int i;
memcpy(early_top_pgt, init_top_pgt, sizeof(early_top_pgt));
@@ -384,6 +384,7 @@ void __init kasan_init(void)
}
shadow_cea_begin = kasan_mem_to_shadow_align_down(CPU_ENTRY_AREA_BASE);
+ shadow_cea_per_cpu_begin = kasan_mem_to_shadow_align_up(CPU_ENTRY_AREA_PER_CPU);
shadow_cea_end = kasan_mem_to_shadow_align_up(CPU_ENTRY_AREA_BASE +
CPU_ENTRY_AREA_MAP_SIZE);
@@ -409,6 +410,15 @@ void __init kasan_init(void)
kasan_mem_to_shadow((void *)VMALLOC_END + 1),
(void *)shadow_cea_begin);
+ /*
+ * Populate the shadow for the shared portion of the CPU entry area.
+ * Shadows for the per-CPU areas are mapped on-demand, as each CPU's
+ * area is randomly placed somewhere in the 512GiB range and mapping
+ * the entire 512GiB range is prohibitively expensive.
+ */
+ kasan_populate_shadow(shadow_cea_begin,
+ shadow_cea_per_cpu_begin, 0);
+
kasan_populate_early_shadow((void *)shadow_cea_end,
kasan_mem_to_shadow((void *)__START_KERNEL_map));