[PATCH 6.1 018/219] ACPI: extlog: fix NULL pointer dereference check

Greg Kroah-Hartman
2024-02-03T04:09:02Z

From: Prarit Bhargava <prarit@redhat.com>

[ Upstream commit 72d9b9747e78979510e9aafdd32eb99c7aa30dd1 ]

The gcc plugin -fanalyzer [1] tries to detect various
patterns of incorrect behaviour. The tool reports:

drivers/acpi/acpi_extlog.c: In function ‘extlog_exit’:
drivers/acpi/acpi_extlog.c:307:12: warning: check of ‘extlog_l1_addr’ for NULL after already dereferencing it [-Wanalyzer-deref-before-check]
|
| 306 | ((struct extlog_l1_head *)extlog_l1_addr)->flags &= ~FLAG_OS_OPTIN;
| | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~
| | |
| | (1) pointer ‘extlog_l1_addr’ is dereferenced here
| 307 | if (extlog_l1_addr)
| | ~
| | |
| | (2) pointer ‘extlog_l1_addr’ is checked for NULL here but it was already dereferenced at (1)
|

Fix the NULL pointer dereference check in extlog_exit().

Link: https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/Static-Analyzer-Options.html # [1]

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/acpi/acpi_extlog.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/acpi_extlog.c b/drivers/acpi/acpi_extlog.c
index 088db2356998..0a84d5afd37c 100644
--- a/drivers/acpi/acpi_extlog.c
+++ b/drivers/acpi/acpi_extlog.c
@@ -308,9 +308,10 @@ static int __init extlog_init(void)
static void __exit extlog_exit(void)
{
mce_unregister_decode_chain(&extlog_mce_dec);
- ((struct extlog_l1_head *)extlog_l1_addr)->flags &= ~FLAG_OS_OPTIN;
- if (extlog_l1_addr)
+ if (extlog_l1_addr) {
+ ((struct extlog_l1_head *)extlog_l1_addr)->flags &= ~FLAG_OS_OPTIN;
acpi_os_unmap_iomem(extlog_l1_addr, l1_size);
+ }
if (elog_addr)
acpi_os_unmap_iomem(elog_addr, elog_size);
release_mem_region(elog_base, elog_size);
--
2.43.0