Since f06bdd4001c2 ("x86/mm: Adapt MODULES_END based on fixmap section size")
kasan_mem_to_shadow(MODULES_END) could be not aligned to a page boundary.
So passing page unaligned address to kasan_populate_zero_shadow() have two
possible effects:
1) It may leave one page hole in supposed to be populated area. After commit
21506525fb8d ("x86/kasan/64: Teach KASAN about the cpu_entry_area") that
hole happens to be in the shadow covering fixmap area and leads to crash:
BUG: unable to handle kernel paging request at fffffbffffe8ee04
RIP: 0010:check_memory_region+0x5c/0x190
Call Trace:
<NMI>
memcpy+0x1f/0x50
ghes_copy_tofrom_phys+0xab/0x180
ghes_read_estatus+0xfb/0x280
ghes_notify_nmi+0x2b2/0x410
nmi_handle+0x115/0x2c0
default_do_nmi+0x57/0x110
do_nmi+0xf8/0x150
end_repeat_nmi+0x1a/0x1e
Note, the crash likely disappeared after commit 92a0f81d8957, which
changed kasan_populate_zero_shadow() call the way it was before
commit 21506525fb8d.
2) Attempt to load module near MODULES_END will fail, because
__vmalloc_node_range() called from kasan_module_alloc() will hit the
WARN_ON(!pte_none(*pte)) in the vmap_pte_range() and bail out with error.
To fix this we need to make kasan_mem_to_shadow(MODULES_END) page aligned
which means that MODULES_END should be 8*PAGE_SIZE aligned.
The whole point of commit f06bdd4001c2 was to move MODULES_END down if
NR_CPUS is big, so the cpu_entry_area takes a lot of space.
But since 92a0f81d8957 ("x86/cpu_entry_area: Move it out of the fixmap")
the cpu_entry_area is no longer in fixmap, so we could just set
MODULES_END to a fixed 8*PAGE_SIZE aligned address.
Reported-by: Jakub Kicinski <kubakici@xxxxx>
Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 4.14
---
Documentation/x86/x86_64/mm.txt | 5 +----
arch/x86/include/asm/pgtable_64_types.h | 2 +-
2 files changed, 2 insertions(+), 5 deletions(-)
diff --git a/Documentation/x86/x86_64/mm.txt b/Documentation/x86/x86_64/mm.txt
index 51101708a03a..60a0fa2bc01f 100644
--- a/Documentation/x86/x86_64/mm.txt
+++ b/Documentation/x86/x86_64/mm.txt
@@ -42,7 +42,7 @@ ffffff0000000000 - ffffff7fffffffff (=39 bits) %esp fixup stacks
ffffffef00000000 - fffffffeffffffff (=64 GB) EFI region mapping space
... unused hole ...
ffffffff80000000 - ffffffff9fffffff (=512 MB) kernel text mapping, from phys 0
-ffffffffa0000000 - [fixmap start] (~1526 MB) module mapping space
+ffffffffa0000000 - fffffffffeffffff (1520 MB) module mapping space
[fixmap start] - ffffffffff5fffff kernel-internal fixmap range
ffffffffff600000 - ffffffffff600fff (=4 kB) legacy vsyscall ABI
ffffffffffe00000 - ffffffffffffffff (=2 MB) unused hole
@@ -66,9 +66,6 @@ memory window (this size is arbitrary, it can be raised later if needed).
The mappings are not part of any other kernel PGD and are only available
during EFI runtime calls.
-The module mapping space size changes based on the CONFIG requirements for the
-following fixmap section.
-
Note that if CONFIG_RANDOMIZE_MEMORY is enabled, the direct mapping of all
physical memory, vmalloc/ioremap space and virtual memory map are randomized.
Their order is preserved but their base will be offset early at boot time.
diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h
index 3d27831bc58d..ed2da4e7f259 100644
--- a/arch/x86/include/asm/pgtable_64_types.h
+++ b/arch/x86/include/asm/pgtable_64_types.h
@@ -100,7 +100,7 @@ typedef struct { pteval_t pte; } pte_t;
#define MODULES_VADDR (__START_KERNEL_map + KERNEL_IMAGE_SIZE)
/* The module sections ends with the start of the fixmap */
-#define MODULES_END __fix_to_virt(__end_of_fixed_addresses + 1)
+#define MODULES_END _AC(0xffffffffff000000, UL)
#define MODULES_LEN (MODULES_END - MODULES_VADDR)
#define ESPFIX_PGD_ENTRY _AC(-2, UL)
--
2.13.6