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From:   Lv Yunlong <lyl2019@mail.ustc.edu.cn>
To:     robert.moore@intel.com, erik.kaneda@intel.com,
        rafael.j.wysocki@intel.com, lenb@kernel.org
Cc:     linux-acpi@vger.kernel.org, devel@acpica.org,
        linux-kernel@vger.kernel.org, Lv Yunlong <lyl2019@mail.ustc.edu.cn>
Subject: [PATCH] ACPICA:dbnames: Fix a error free in acpi_db_walk_for_fields
Date:   Mon, 26 Apr 2021 18:41:34 -0700
Message-Id: <20210427014134.3568-1-lyl2019@mail.ustc.edu.cn>
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In acpi_db_walk_for_fields, buffer.pointer is freed in the first
time via ACPI_FREE() after acpi_os_printf("%s ", (char *)buffer.pointer).
But later, buffer.pointer is assigned to ret_value, and the freed
pointer is dereferenced by ret_value, which is use after free.

In addition, buffer.pointer is freed by ACPI_FREE() again after
acpi_os_printf("}\n"), which is a double free.

My patch removes the first ACPI_FREE() to avoid the uaf and double
free bugs.

Fixes: 5fd033288a866 ("ACPICA: debugger: add command to dump all fields of particular subtype")
Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
---
 drivers/acpi/acpica/dbnames.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/acpi/acpica/dbnames.c b/drivers/acpi/acpica/dbnames.c
index 3615e1a6efd8..dabd76df15ec 100644
--- a/drivers/acpi/acpica/dbnames.c
+++ b/drivers/acpi/acpica/dbnames.c
@@ -547,7 +547,6 @@ acpi_db_walk_for_fields(acpi_handle obj_handle,
 	}
 
 	acpi_os_printf("%s ", (char *)buffer.pointer);
-	ACPI_FREE(buffer.pointer);
 
 	buffer.length = ACPI_ALLOCATE_LOCAL_BUFFER;
 	acpi_evaluate_object(obj_handle, NULL, NULL, &buffer);
-- 
2.25.1