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kho: verify deserialization status and fix FDT alignment access

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During boot, kho_restore_folio() relies on the memory map having been
successfully deserialized.  If deserialization fails or no map is present,
attempting to restore the FDT folio is unsafe.

Update kho_mem_deserialize() to return a boolean indicating success.  Use
this return value in kho_memory_init() to disable KHO if deserialization
fails.  Also, the incoming FDT folio is never used, there is no reason to
restore it.

Additionally, use get_unaligned() to retrieve the memory map pointer from
the FDT.  FDT properties are not guaranteed to be naturally aligned, and
accessing a 64-bit value via a pointer that is only 32-bit aligned can
cause faults.

Link: https://lkml.kernel.org/r/20251114190002.3311679-6-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Baoquan He <bhe@redhat.com>
Cc: Coiby Xu <coxu@redhat.com>
Cc: Dave Vasilevsky <dave@vasilevsky.ca>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Kees Cook <kees@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Pasha Tatashin
2025-11-14 13:59:54 -05:00
committed by Andrew Morton
parent 85de0090bd
commit 53f8f064eb
1 changed files with 19 additions and 13 deletions
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32
kernel/liveupdate/kexec_handover.c
View File

@@ -18,6 +18,7 @@
#include <linux/list.h>
#include <linux/memblock.h>
#include <linux/page-isolation.h>
#include <linux/unaligned.h>
#include <linux/vmalloc.h>
#include <asm/early_ioremap.h>
@@ -451,20 +452,27 @@ static void __init deserialize_bitmap(unsigned int order,
}
}
static void __init kho_mem_deserialize(const void *fdt)
/* Return true if memory was deserizlied */
static bool __init kho_mem_deserialize(const void *fdt)
{
struct khoser_mem_chunk *chunk;
const phys_addr_t *mem;
const void *mem_ptr;
u64 mem;
int len;
mem = fdt_getprop(fdt, 0, PROP_PRESERVED_MEMORY_MAP, &len);
if (!mem || len != sizeof(*mem)) {
mem_ptr = fdt_getprop(fdt, 0, PROP_PRESERVED_MEMORY_MAP, &len);
if (!mem_ptr || len != sizeof(u64)) {
pr_err("failed to get preserved memory bitmaps\n");
return;
return false;
}
chunk = *mem ? phys_to_virt(*mem) : NULL;
mem = get_unaligned((const u64 *)mem_ptr);
chunk = mem ? phys_to_virt(mem) : NULL;
/* No preserved physical pages were passed, no deserialization */
if (!chunk)
return false;
while (chunk) {
unsigned int i;
@@ -473,6 +481,8 @@ static void __init kho_mem_deserialize(const void *fdt)
&chunk->bitmaps[i]);
chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
}
return true;
}
/*
@@ -1458,16 +1468,12 @@ static void __init kho_release_scratch(void)
void __init kho_memory_init(void)
{
struct folio *folio;
if (kho_in.scratch_phys) {
kho_scratch = phys_to_virt(kho_in.scratch_phys);
kho_release_scratch();
kho_mem_deserialize(kho_get_fdt());
folio = kho_restore_folio(kho_in.fdt_phys);
if (!folio)
pr_warn("failed to restore folio for KHO fdt\n");
if (!kho_mem_deserialize(kho_get_fdt()))
kho_in.fdt_phys = 0;
} else {
kho_reserve_scratch();
}