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    Subject[PATCH AUTOSEL 5.10 6/8] ACPI: extlog: fix NULL pointer dereference check
    Date
    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 e648158368a7..ac89bc85a9c9 100644
    --- a/drivers/acpi/acpi_extlog.c
    +++ b/drivers/acpi/acpi_extlog.c
    @@ -303,9 +303,10 @@ 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

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