mm,ima,kexec: use memblock_free_late from ima_free_kexec_buffer

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 [email protected]

Signed-off-by Rik van Riel <[email protected]>

Suggested-by Mike Rappoport <[email protected]>

---
 arch/x86/kernel/setup.c | 8 ++------
 drivers/of/kexec.c      | 3 ++-
 2 files changed, 4 insertions(+), 7 deletions(-)

arch/x86/kernel/setup.c +2 -6

index fd975a4a5200..aa0df37c1fe7 100644
@@ -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;

drivers/of/kexec.c +2 -1

index f26d2ba8a371..68278340cecf 100644
@@ -184,7 +184,8 @@ int __init ima_free_kexec_buffer(void)
 	if (ret)
 		return ret;
 
-	return memblock_phys_free(addr, size);
+	memblock_free_late(addr, size);
+	return 0;
 }
 #endif
 

Signature · 1 line

2.41.0

Quoted 8 lines · 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.

Quoted 5 lines

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")

Fixes b69a2afd5afc ("x86/kexec: Carry forward IMA measurement log on

kexec")

Acked-by Rob Herring <[email protected]>

(I'm assuming someone else is taking this)

Quoted 9 lines · Rob Herring

Quoted 8 lines · 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.

Quoted 9 lines

Quoted 5 lines

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")

Fixes b69a2afd5afc ("x86/kexec: Carry forward IMA measurement log on

kexec")

Thank you for digging further back in the history of that code.

Quoted 3 lines

Acked-by Rob Herring <[email protected]>

(I'm assuming someone else is taking this)

I hope so, but I don't know who...