Kyle has reported that kernel crashes sometimes when it boots in
5-level paging mode with KASLR enabled:
[ 0.000000] WARNING: CPU: 0 PID: 0 at arch/x86/mm/init_64.c:87
phys_p4d_init+0x1d4/0x1ea
[ 0.000000] Modules linked in:
[ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.2.0-rc5+ #27
[ 0.000000] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.12.0-0-ga698c8995f-prebuilt.qemu.4
[ 0.000000] RIP: 0010:phys_p4d_init+0x1d4/0x1ea
[ 0.000000] Code: 20 be 43 94 ff 45 cc 4c 89 e6 e9 90 fe ff ff 48 89 d8 eb
1d 48 8b 4d d0 48 8b 7d c0 45 0f b6 3
[ 0.000000] RSP: 0000:ffffffff94403c70 EFLAGS: 00000046 ORIG_RAX:
0000000000000000
[ 0.000000] RAX: 0000000000000000 RBX: 0000000340000000 RCX: 0000000000000007
[ 0.000000] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
[ 0.000000] RBP: ffffffff94403cb8 R08: 0000000000000023 R09: ffffffff947fa680
[ 0.000000] R10: 0000000000000008 R11: 0000000000000031 R12: 0000010000000000
[ 0.000000] R13: 0000000340000000 R14: ffffffff94403d01 R15: ff484d01962014d0
[ 0.000000] FS: 0000000000000000(0000) GS:ffffffff9468a000(0000)
knlGS:0000000000000000
[ 0.000000] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 0.000000] CR2: ff484d0196201000 CR3: 0000000315b3e000 CR4: 00000000000016b0
[ 0.000000] Call Trace:
[ 0.000000] __kernel_physical_mapping_init+0x10a/0x35c
[ 0.000000] kernel_physical_mapping_init+0xe/0x10
[ 0.000000] init_memory_mapping+0x1aa/0x3b0
[ 0.000000] init_range_memory_mapping+0xc8/0x116
[ 0.000000] init_mem_mapping+0x225/0x2eb
[ 0.000000] setup_arch+0x6ff/0xcf5
[ 0.000000] start_kernel+0x64/0x53b
[ 0.000000] ? copy_bootdata+0x1f/0xce
[ 0.000000] x86_64_start_reservations+0x24/0x26
[ 0.000000] x86_64_start_kernel+0x8a/0x8d
[ 0.000000] secondary_startup_64+0xb6/0xc0
[ 0.000000] random: get_random_bytes called from
print_oops_end_marker+0x3f/0x60 with crng_init=0
...
[ 0.000000] BUG: unable to handle page fault for address: ff484d019580eff8
[ 0.000000] #PF: supervisor read access in kernel mode
[ 0.000000] #PF: error_code(0x0000) - not-present page
[ 0.000000] BAD
[ 0.000000] Oops: 0000 [#1] SMP NOPTI
[ 0.000000] CPU: 0 PID: 0 Comm: swapper Tainted: G W
5.2.0-rc5+ #27
[ 0.000000] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.12.0-0-ga698c8995f-prebuilt.qemu.4
[ 0.000000] RIP: 0010:fill_pud+0x13/0x130
[ 0.000000] Code: 48 83 c4 08 b8 f4 ff ff ff 5b 41 5c 41 5d 41 5e 41 5f 5d
c3 31 c0 c3 e8 2b ee d8 00 55 48 89 4
[ 0.000000] RSP: 0000:ffffffff94403dc0 EFLAGS: 00000006
[ 0.000000] RAX: 00000000000001ff RBX: ffffffffff5fd000 RCX: 0000000000000030
[ 0.000000] RDX: 00000000000001ff RSI: ffffffffff5fd000 RDI: ff484d019580eff8
[ 0.000000] RBP: ffffffff94403de0 R08: 0000000000000078 R09: 0000000000000002
[ 0.000000] R10: ffffffff94403cb0 R11: 000000000000005b R12: ff484d019580eff8
[ 0.000000] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
[ 0.000000] FS: 0000000000000000(0000) GS:ffffffff9468a000(0000)
knlGS:0000000000000000
[ 0.000000] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 0.000000] CR2: ff484d019580aa40 CR3: 000000031580a000 CR4: 00000000000016b0
[ 0.000000] Call Trace:
[ 0.000000] set_pte_vaddr_p4d+0x2e/0x50
[ 0.000000] set_pte_vaddr+0x6f/0xb0
[ 0.000000] __native_set_fixmap+0x28/0x40
[ 0.000000] native_set_fixmap+0x39/0x70
[ 0.000000] register_lapic_address+0x49/0xb6
[ 0.000000] early_acpi_boot_init+0xa5/0xde
[ 0.000000] setup_arch+0x944/0xcf5
[ 0.000000] start_kernel+0x64/0x53b
[ 0.000000] ? copy_bootdata+0x1f/0xce
[ 0.000000] x86_64_start_reservations+0x24/0x26
[ 0.000000] x86_64_start_kernel+0x8a/0x8d
[ 0.000000] secondary_startup_64+0xb6/0xc0
[ 0.000000] Modules linked in:
[ 0.000000] CR2: ff484d019580eff8
Kyle bisected the issue to commmit b569c1843498 ("x86/mm/KASLR: Reduce
randomization granularity for 5-level paging to 1GB")
The commit relaxes KASLR alignment requirements and it can lead to
mismatch bentween 'i' and 'p4d_index(vaddr)' inside the loop in
phys_p4d_init(). The mismatch in its turn leads to clearing wrong p4d
entry and eventually to the oops.
The fix is to make phys_p4d_init() walk virtual address space, not
physical one.
Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
Reported-and-tested-by: Kyle Pelton <kyle.d.pel...@intel.com>
Fixes: b569c1843498 ("x86/mm/KASLR: Reduce randomization granularity for
5-level paging to 1GB")
Cc: Baoquan He <b...@redhat.com>
---
arch/x86/mm/init_64.c | 39 ++++++++++++++++-----------------------
1 file changed, 16 insertions(+), 23 deletions(-)
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 693aaf28d5fe..4628ac9105a2 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -671,41 +671,34 @@ static unsigned long __meminit
phys_p4d_init(p4d_t *p4d_page, unsigned long paddr, unsigned long paddr_end,
unsigned long page_size_mask, bool init)
{
- unsigned long paddr_next, paddr_last = paddr_end;
- unsigned long vaddr = (unsigned long)__va(paddr);
- int i = p4d_index(vaddr);
+ unsigned long vaddr, vaddr_start, vaddr_end, vaddr_next, paddr_last;
+
+ paddr_last = paddr_end;
+ vaddr = (unsigned long)__va(paddr);
+ vaddr_end = (unsigned long)__va(paddr_end);
+ vaddr_start = vaddr;
if (!pgtable_l5_enabled())
return phys_pud_init((pud_t *) p4d_page, paddr, paddr_end,
page_size_mask, init);
- for (; i < PTRS_PER_P4D; i++, paddr = paddr_next) {
- p4d_t *p4d;
+ for (; vaddr < vaddr_end; vaddr = vaddr_next) {
+ p4d_t *p4d = p4d_page + p4d_index(vaddr);
pud_t *pud;
- vaddr = (unsigned long)__va(paddr);
- p4d = p4d_page + p4d_index(vaddr);
- paddr_next = (paddr & P4D_MASK) + P4D_SIZE;
+ vaddr_next = (vaddr & P4D_MASK) + P4D_SIZE;
- if (paddr >= paddr_end) {
- if (!after_bootmem &&
- !e820__mapped_any(paddr & P4D_MASK, paddr_next,
- E820_TYPE_RAM) &&
- !e820__mapped_any(paddr & P4D_MASK, paddr_next,
- E820_TYPE_RESERVED_KERN))
- set_p4d_init(p4d, __p4d(0), init);
- continue;
- }
-
- if (!p4d_none(*p4d)) {
- pud = pud_offset(p4d, 0);
- paddr_last = phys_pud_init(pud, paddr, paddr_end,
- page_size_mask, init);
+ if (p4d_val(*p4d)) {
+ pud = (pud_t *)p4d_page_vaddr(*p4d);
+ paddr_last = phys_pud_init(pud, __pa(vaddr),
+ __pa(vaddr_end),
+ page_size_mask,
+ init);
continue;
}
pud = alloc_low_page();
- paddr_last = phys_pud_init(pud, paddr, paddr_end,
+ paddr_last = phys_pud_init(pud, __pa(vaddr), __pa(vaddr_end),
page_size_mask, init);
spin_lock(&init_mm.page_table_lock);
--
2.21.0
