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kho: preserve FDT folio only once during initialization

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Currently, the FDT folio is preserved inside __kho_finalize().  If the
user performs multiple finalize/abort cycles, kho_preserve_folio() is
called repeatedly for the same FDT folio.

Since the FDT folio is allocated once during kho_init(), it should be
marked for preservation at the same time.  Move the preservation call to
kho_init() to align the preservation state with the object's lifecycle and
simplify the finalize path.

Also, pre-zero the FDT tree so we do not expose random bits to the user
and to the next kernel by using the new kho_alloc_preserve() api.

Link: https://lkml.kernel.org/r/20251114190002.3311679-5-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 13:59:53 -05:00 committed by Andrew Morton
parent 4c205677af
commit 85de0090bd
1 changed files with 6 additions and 12 deletions
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18
kernel/liveupdate/kexec_handover.c
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@ -1251,10 +1251,6 @@ static int __kho_finalize(void)
if (err)
goto abort;
err = kho_preserve_folio(virt_to_folio(kho_out.fdt));
if (err)
goto abort;
err = kho_mem_serialize(&kho_out);
if (err)
goto abort;
@ -1384,19 +1380,17 @@ EXPORT_SYMBOL_GPL(kho_retrieve_subtree);
static __init int kho_init(void)
{
int err = 0;
const void *fdt = kho_get_fdt();
struct page *fdt_page;
int err = 0;
if (!kho_enable)
return 0;
fdt_page = alloc_page(GFP_KERNEL);
if (!fdt_page) {
err = -ENOMEM;
kho_out.fdt = kho_alloc_preserve(PAGE_SIZE);
if (IS_ERR(kho_out.fdt)) {
err = PTR_ERR(kho_out.fdt);
goto err_free_scratch;
}
kho_out.fdt = page_to_virt(fdt_page);
err = kho_debugfs_init();
if (err)
@ -1424,9 +1418,9 @@ static __init int kho_init(void)
return 0;
err_free_fdt:
put_page(fdt_page);
kho_out.fdt = NULL;
kho_unpreserve_free(kho_out.fdt);
err_free_scratch:
kho_out.fdt = NULL;
for (int i = 0; i < kho_scratch_cnt; i++) {
void *start = __va(kho_scratch[i].addr);
void *end = start + kho_scratch[i].size;