linux-kernel - [PATCH] ACPICA: Linuxize: Fix a NULL pointer dereference in acpi_db_convert_to

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Date:   Tue, 25 Jan 2022 00:40:14 +0800
From:   Zhou Qingyang <zhou1615@....edu>
To:     zhou1615@....edu
Cc:     kjlu@....edu, Robert Moore <robert.moore@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Len Brown <lenb@...nel.org>, Lv Zheng <lv.zheng@...el.com>,
        linux-acpi@...r.kernel.org, devel@...ica.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] ACPICA: Linuxize: Fix a NULL pointer dereference in acpi_db_convert_to_package()

In acpi_db_convert_to_package(), the variable elements is assigned by
ACPI_ALLOCATE_ZEROED() and passes its address to 
acpi_db_convert_to_object(). In that function we may have a dereference
of elements without checks. ACPI_ALLOCATE_ZEROED() would return NULL on
failure, which may lead to NULL pointer dereference.

Fix this bug by adding a NULL check of elements.

This bug was found by a static analyzer.

Builds with 'make allyesconfig' show no new warnings,
and our static analyzer no longer warns about this code.

Fixes: 995751025572 ("ACPICA: Linuxize: Export debugger files to Linux")
Signed-off-by: Zhou Qingyang <zhou1615@....edu>
---
The analysis employs differential checking to identify inconsistent 
security operations (e.g., checks or kfrees) between two code paths 
and confirms that the inconsistent operations are not recovered in the
current function or the callers, so they constitute bugs. 

Note that, as a bug found by static analysis, it can be a false
positive or hard to trigger. Multiple researchers have cross-reviewed
the bug.

 drivers/acpi/acpica/dbconvert.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/acpi/acpica/dbconvert.c b/drivers/acpi/acpica/dbconvert.c
index 2b84ac093698..8dbab6932049 100644
--- a/drivers/acpi/acpica/dbconvert.c
+++ b/drivers/acpi/acpica/dbconvert.c
@@ -174,6 +174,8 @@ acpi_status acpi_db_convert_to_package(char *string, union acpi_object *object)
 	elements =
 	    ACPI_ALLOCATE_ZEROED(DB_DEFAULT_PKG_ELEMENTS *
 				 sizeof(union acpi_object));
+	if (!elements)
+		return (AE_NO_MEMORY);

 	this = string;
 	for (i = 0; i < (DB_DEFAULT_PKG_ELEMENTS - 1); i++) {
-- 
2.25.1