[PATCH] mm,kexec,ima,x86: use memblock_free_late from ima_free_kexec_buffer

[Rik van Riel]

The code calling ima_free_kexec_buffer runs long after the memblock
allocator has already been torn down, potentially resulting in a use
after free in memblock_isolate_range.

With KASAN or KFENCE, this use after free will result in a BUG
from the idle task, and a subsequent kernel panic.

Switch ima_free_kexec_buffer over to memblock_free_late to avoid
that issue.

Fixes: fee3ff99bc67 ("powerpc: Move arch independent ima kexec functions to drivers/of/kexec.c")
Cc: stable@xxxxxxxxxx
Signed-off-by: Rik van Riel <riel@xxxxxxxxxxx>
Suggested-by: Mike Rappoport <rppt@xxxxxxxxxx>
---
 arch/x86/kernel/setup.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index fd975a4a5200..aa0df37c1fe7 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -359,15 +359,11 @@ static void __init add_early_ima_buffer(u64 phys_addr)
 #if defined(CONFIG_HAVE_IMA_KEXEC) && !defined(CONFIG_OF_FLATTREE)
 int __init ima_free_kexec_buffer(void)
 {
-	int rc;
-
 	if (!ima_kexec_buffer_size)
 		return -ENOENT;
 
-	rc = memblock_phys_free(ima_kexec_buffer_phys,
-				ima_kexec_buffer_size);
-	if (rc)
-		return rc;
+	memblock_free_late(ima_kexec_buffer_phys,
+			   ima_kexec_buffer_size);
 
 	ima_kexec_buffer_phys = 0;
 	ima_kexec_buffer_size = 0;
-- 
2.41.0