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ACPI: extlog: fix NULL pointer dereference check

Mark Langsdorf requested to merge mlangsdorf/centos-stream-9:jira29112 into main

JIRA: https://issues.redhat.com/browse/RHEL-29112
CVE: CVE-2023-52605

commit 72d9b9747e78979510e9aafdd32eb99c7aa30dd1
Author: Prarit Bhargava prarit@redhat.com
Date: Mon Dec 4 13:00:37 2023 -0500

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: Mark Langsdorf mlangsdo@redhat.com

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