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mm/vmalloc: export clear_vm_uninitialized_flag()

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Patch series "Fix KASAN support for KHO restored vmalloc regions".

When KHO restores a vmalloc area, it maps existing physical pages into a
newly allocated virtual memory area.  However, because these areas were
not properly unpoisoned, KASAN would treat any access to the restored
region as out-of-bounds, as seen in the following trace:

BUG: KASAN: vmalloc-out-of-bounds in kho_test_restore_data.isra.0+0x17b/0x2cd
Read of size 8 at addr ffffc90000025000 by task swapper/0/1
[...]
Call Trace:
[...]
kasan_report+0xe8/0x120
kho_test_restore_data.isra.0+0x17b/0x2cd
kho_test_init+0x15a/0x1f0
do_one_initcall+0xd5/0x4b0

The fix involves deferring KASAN's default poisoning by using the
VM_UNINITIALIZED flag during allocation, manually unpoisoning the memory
once it is correctly mapped, and then clearing the uninitialized flag
using a newly exported helper.


This patch (of 2):

Make clear_vm_uninitialized_flag() available to other parts of the kernel
that need to manage vmalloc areas manually, such as KHO for restoring
vmallocs.

Link: https://lkml.kernel.org/r/20260225220223.1695350-1-pasha.tatashin@soleen.com
Link: https://lkml.kernel.org/r/20260225223857.1714801-2-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Pasha Tatashin
2026-02-25 17:38:56 -05:00
committed by Andrew Morton
parent da735962d0
commit ec10636539
2 changed files with 3 additions and 1 deletions
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2
mm/internal.h
View File

@@ -1469,6 +1469,8 @@ int __must_check vmap_pages_range_noflush(unsigned long addr, unsigned long end,
}
#endif
void clear_vm_uninitialized_flag(struct vm_struct *vm);
int __must_check __vmap_pages_range_noflush(unsigned long addr,
unsigned long end, pgprot_t prot,
struct page **pages, unsigned int page_shift);

2
mm/vmalloc.c
View File

@@ -3183,7 +3183,7 @@ void __init vm_area_register_early(struct vm_struct *vm, size_t align)
kasan_populate_early_vm_area_shadow(vm->addr, vm->size);
}
static void clear_vm_uninitialized_flag(struct vm_struct *vm)
void clear_vm_uninitialized_flag(struct vm_struct *vm)
{
/*
* Before removing VM_UNINITIALIZED,