linux-kernel - [PATCH 6.0 16/20] efi: ssdt: Dont free memory if ACPI table was loaded successfully

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Date:   Mon, 24 Oct 2022 13:31:18 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Amadeusz Sławiński 
        <amadeuszx.slawinski@...ux.intel.com>,
        Ard Biesheuvel <ardb@...nel.org>
Subject: [PATCH 6.0 16/20] efi: ssdt: Dont free memory if ACPI table was loaded successfully

From: Ard Biesheuvel <ardb@...nel.org>

commit 4b017e59f01097f19b938f6dc4dc2c4720701610 upstream.

Amadeusz reports KASAN use-after-free errors introduced by commit
3881ee0b1edc ("efi: avoid efivars layer when loading SSDTs from
variables"). The problem appears to be that the memory that holds the
new ACPI table is now freed unconditionally, instead of only when the
ACPI core reported a failure to load the table.

So let's fix this, by omitting the kfree() on success.

Cc: <stable@...r.kernel.org> # v6.0
Link: https://lore.kernel.org/all/a101a10a-4fbb-5fae-2e3c-76cf96ed8fbd@linux.intel.com/
Fixes: 3881ee0b1edc ("efi: avoid efivars layer when loading SSDTs from variables")
Reported-by: Amadeusz Sławiński <amadeuszx.slawinski@...ux.intel.com>
Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/firmware/efi/efi.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -269,6 +269,8 @@ static __init int efivar_ssdt_load(void)
 			acpi_status ret = acpi_load_table(data, NULL);
 			if (ret)
 				pr_err("failed to load table: %u\n", ret);
+			else
+				continue;
 		} else {
 			pr_err("failed to get var data: 0x%lx\n", status);
 		}