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Date:   Thu, 20 Jul 2023 10:14:31 -0400
From:   Rik van Riel <riel@surriel.com>
To:     linux-kernel@vger.kernel.org
Cc:     kernel-team@meta.com, Mike Rapoport <rppt@kernel.org>,
        devicetree@vger.kernel.org, x86@kernel.org,
        Rob Herring <robh+dt@kernel.org>,
        Juergen Gross <jgross@suse.com>,
        Dave Hansen <dave.hansen@linux.intel.com>
Subject: [PATCH] mm,ima,kexec: use memblock_free_late from
 ima_free_kexec_buffer
Message-ID: <20230720101431.71640c8a@imladris.surriel.com>
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Sender: riel@surriel.com
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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@kernel.org
Signed-off-by: Rik van Riel <riel@surriel.com>
Suggested-by: Mike Rappoport <rppt@kernel.org>
---
 arch/x86/kernel/setup.c | 8 ++------
 drivers/of/kexec.c      | 3 ++-
 2 files changed, 4 insertions(+), 7 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;
diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
index f26d2ba8a371..68278340cecf 100644
--- a/drivers/of/kexec.c
+++ b/drivers/of/kexec.c
@@ -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
 
-- 
2.41.0