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authorThomas Gleixner2024-08-14 00:29:36 +0200
committerThomas Gleixner2024-08-20 13:44:57 +0200
commitea72ce5da22806d5713f3ffb39a6d5ae73841f93 (patch)
tree73b96bc7ae1c4c36915301ccf1086a5f9d24cd83 /mm
parent2848ff28d180bd63a95da8e5dcbcdd76c1beeb7b (diff)
x86/kaslr: Expose and use the end of the physical memory address space
iounmap() on x86 occasionally fails to unmap because the provided valid ioremap address is not below high_memory. It turned out that this happens due to KASLR. KASLR uses the full address space between PAGE_OFFSET and vaddr_end to randomize the starting points of the direct map, vmalloc and vmemmap regions. It thereby limits the size of the direct map by using the installed memory size plus an extra configurable margin for hot-plug memory. This limitation is done to gain more randomization space because otherwise only the holes between the direct map, vmalloc, vmemmap and vaddr_end would be usable for randomizing. The limited direct map size is not exposed to the rest of the kernel, so the memory hot-plug and resource management related code paths still operate under the assumption that the available address space can be determined with MAX_PHYSMEM_BITS. request_free_mem_region() allocates from (1 << MAX_PHYSMEM_BITS) - 1 downwards. That means the first allocation happens past the end of the direct map and if unlucky this address is in the vmalloc space, which causes high_memory to become greater than VMALLOC_START and consequently causes iounmap() to fail for valid ioremap addresses. MAX_PHYSMEM_BITS cannot be changed for that because the randomization does not align with address bit boundaries and there are other places which actually require to know the maximum number of address bits. All remaining usage sites of MAX_PHYSMEM_BITS have been analyzed and found to be correct. Cure this by exposing the end of the direct map via PHYSMEM_END and use that for the memory hot-plug and resource management related places instead of relying on MAX_PHYSMEM_BITS. In the KASLR case PHYSMEM_END maps to a variable which is initialized by the KASLR initialization and otherwise it is based on MAX_PHYSMEM_BITS as before. To prevent future hickups add a check into add_pages() to catch callers trying to add memory above PHYSMEM_END. Fixes: 0483e1fa6e09 ("x86/mm: Implement ASLR for kernel memory regions") Reported-by: Max Ramanouski <max8rr8@gmail.com> Reported-by: Alistair Popple <apopple@nvidia.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-By: Max Ramanouski <max8rr8@gmail.com> Tested-by: Alistair Popple <apopple@nvidia.com> Reviewed-by: Dan Williams <dan.j.williams@intel.com> Reviewed-by: Alistair Popple <apopple@nvidia.com> Reviewed-by: Kees Cook <kees@kernel.org> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/87ed6soy3z.ffs@tglx
Diffstat (limited to 'mm')
-rw-r--r--mm/memory_hotplug.c2
-rw-r--r--mm/sparse.c2
2 files changed, 2 insertions, 2 deletions
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 66267c26ca1b..951878ab627a 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1681,7 +1681,7 @@ struct range __weak arch_get_mappable_range(void)
struct range mhp_get_pluggable_range(bool need_mapping)
{
- const u64 max_phys = (1ULL << MAX_PHYSMEM_BITS) - 1;
+ const u64 max_phys = PHYSMEM_END;
struct range mhp_range;
if (need_mapping) {
diff --git a/mm/sparse.c b/mm/sparse.c
index e4b830091d13..0c3bff882033 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -129,7 +129,7 @@ static inline int sparse_early_nid(struct mem_section *section)
static void __meminit mminit_validate_memmodel_limits(unsigned long *start_pfn,
unsigned long *end_pfn)
{
- unsigned long max_sparsemem_pfn = 1UL << (MAX_PHYSMEM_BITS-PAGE_SHIFT);
+ unsigned long max_sparsemem_pfn = (PHYSMEM_END + 1) >> PAGE_SHIFT;
/*
* Sanity checks - do not allow an architecture to pass