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Re: [Qemu-devel] [patch] firmware: qemu_fw_cfg.c: potential unintialized

From: Gabriel L. Somlo
Subject: Re: [Qemu-devel] [patch] firmware: qemu_fw_cfg.c: potential unintialized variable
Date: Thu, 14 Apr 2016 14:40:06 -0400
User-agent: Mutt/1.5.24 (2015-08-30)

On Thu, Apr 14, 2016 at 12:33:37PM +0300, Dan Carpenter wrote:
> It acpi_acquire_global_lock() return AE_NOT_CONFIGURED then "glk" isn't
  ^                               ^
  If                            returns

> initialized, which, if you got very unlucky, could cause a bug.

In principle I'm OK with being cautious and initializing local
variables just in case, but I'm curious:

acpi_acquire_global_lock() (and its friend, acpi_release_global_lock())
are both wrapped inside the same macro -- ACPI_HW_DEPENDENT_RETURN_STATUS
-- which either makes them both do something useful, or makes them both
no-ops returning a hardcoded AE_NOT_CONFIGURED.

So what else do you think could be a way to get very unlucky ?

Otherwise, sure: Just 'cause we're paranoid doesn't mean someone's not
out to get us! :)


> Signed-off-by: Dan Carpenter <address@hidden>
> diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
> index d999fe3..0e20116 100644
> --- a/drivers/firmware/qemu_fw_cfg.c
> +++ b/drivers/firmware/qemu_fw_cfg.c
> @@ -77,7 +77,7 @@ static inline u16 fw_cfg_sel_endianness(u16 key)
>  static inline void fw_cfg_read_blob(u16 key,
>                                   void *buf, loff_t pos, size_t count)
>  {
> -     u32 glk;
> +     u32 glk = -1U;
>       acpi_status status;
>       /* If we have ACPI, ensure mutual exclusion against any potential

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