linux-kernel - Re: [PATCH] scsi: qla4xxx: avoid freeing unallocated dma memory

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Date:   Fri, 22 Mar 2019 08:25:04 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     QLogic-Storage-Upstream@...gic.com,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        clang-built-linux@...glegroups.com,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Manish Rangankar <mrangankar@...vell.com>,
        Chengguang Xu <cgxu519@....com>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: qla4xxx: avoid freeing unallocated dma memory

On Fri, Mar 22, 2019 at 03:25:03PM +0100, Arnd Bergmann wrote:
> Clang -Wuninitialized notices that on is_qla40XX we never allocate
> any DMA memory in get_fw_boot_info() but attempt to free it anyway:
> 
> drivers/scsi/qla4xxx/ql4_os.c:5915:7: error: variable 'buf_dma' is used uninitialized whenever 'if' condition is false
>       [-Werror,-Wsometimes-uninitialized]
>                 if (!(val & 0x07)) {
>                     ^~~~~~~~~~~~~
> drivers/scsi/qla4xxx/ql4_os.c:5985:47: note: uninitialized use occurs here
>         dma_free_coherent(&ha->pdev->dev, size, buf, buf_dma);
>                                                      ^~~~~~~
> drivers/scsi/qla4xxx/ql4_os.c:5915:3: note: remove the 'if' if its condition is always true
>                 if (!(val & 0x07)) {
>                 ^~~~~~~~~~~~~~~~~~~
> drivers/scsi/qla4xxx/ql4_os.c:5885:20: note: initialize the variable 'buf_dma' to silence this warning
>         dma_addr_t buf_dma;
>                           ^
>                            = 0
> 
> Skip the call to dma_free_coherent() here.
> 
> Fixes: 2a991c215978 ("[SCSI] qla4xxx: Boot from SAN support for open-iscsi")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

This is what I initially had but I guess I cared too much about that
debug print firing properly :) I like this better personally.

Reviewed-by: Nathan Chancellor <natechancellor@...il.com>

> ---
>  drivers/scsi/qla4xxx/ql4_os.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/qla4xxx/ql4_os.c b/drivers/scsi/qla4xxx/ql4_os.c
> index 16a18d5d856f..daa884fa43f4 100644
> --- a/drivers/scsi/qla4xxx/ql4_os.c
> +++ b/drivers/scsi/qla4xxx/ql4_os.c
> @@ -5928,7 +5928,7 @@ static int get_fw_boot_info(struct scsi_qla_host *ha, uint16_t ddb_index[])
>  		val = rd_nvram_byte(ha, sec_addr);
>  		if (val & BIT_7)
>  			ddb_index[1] = (val & 0x7f);
> -
> +		goto exit_boot_info;
>  	} else if (is_qla80XX(ha)) {
>  		buf = dma_alloc_coherent(&ha->pdev->dev, size,
>  					 &buf_dma, GFP_KERNEL);
> -- 
> 2.20.0
>