KHO allocates metadata for its preserved memory map using the slab allocator via kzalloc(). This metadata is temporary and is used by the next kernel during early boot to find preserved memory.
A problem arises when KFENCE is enabled. kzalloc() calls can be randomly intercepted by kfence_alloc(), which services the allocation from a dedicated KFENCE memory pool. This pool is allocated early in boot via memblock.
When booting via KHO, the memblock allocator is restricted to a "scratch area", forcing the KFENCE pool to be allocated within it. This creates a conflict, as the scratch area is expected to be ephemeral and overwriteable by a subsequent kexec. If KHO metadata is placed in this KFENCE pool, it leads to memory corruption when the next kernel is loaded.
To fix this, modify KHO to allocate its metadata directly from the buddy allocator instead of slab.
Fixes: fc33e4b44b27 ("kexec: enable KHO support for memory preservation") Signed-off-by: Pasha Tatashin pasha.tatashin@soleen.com Reviewed-by: Pratyush Yadav pratyush@kernel.org --- include/linux/gfp.h | 3 +++ kernel/kexec_handover.c | 6 +++--- 2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/include/linux/gfp.h b/include/linux/gfp.h index 0ceb4e09306c..623bee335383 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -7,6 +7,7 @@ #include <linux/mmzone.h> #include <linux/topology.h> #include <linux/alloc_tag.h> +#include <linux/cleanup.h> #include <linux/sched.h>
struct vm_area_struct; @@ -463,4 +464,6 @@ static inline struct folio *folio_alloc_gigantic_noprof(int order, gfp_t gfp, /* This should be paired with folio_put() rather than free_contig_range(). */ #define folio_alloc_gigantic(...) alloc_hooks(folio_alloc_gigantic_noprof(__VA_ARGS__))
+DEFINE_FREE(free_page, void *, free_page((unsigned long)_T)) + #endif /* __LINUX_GFP_H */ diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c index e5b91761fbfe..de4466b47455 100644 --- a/kernel/kexec_handover.c +++ b/kernel/kexec_handover.c @@ -142,7 +142,7 @@ static void *xa_load_or_alloc(struct xarray *xa, unsigned long index) if (res) return res;
- void *elm __free(kfree) = kzalloc(PAGE_SIZE, GFP_KERNEL); + void *elm __free(free_page) = (void *)get_zeroed_page(GFP_KERNEL);
if (!elm) return ERR_PTR(-ENOMEM); @@ -348,9 +348,9 @@ static_assert(sizeof(struct khoser_mem_chunk) == PAGE_SIZE); static struct khoser_mem_chunk *new_chunk(struct khoser_mem_chunk *cur_chunk, unsigned long order) { - struct khoser_mem_chunk *chunk __free(kfree) = NULL; + struct khoser_mem_chunk *chunk __free(free_page) = NULL;
- chunk = kzalloc(PAGE_SIZE, GFP_KERNEL); + chunk = (void *)get_zeroed_page(GFP_KERNEL); if (!chunk) return ERR_PTR(-ENOMEM);