Re: [PATCH] scsi: gdth: Only call dma_free_coherent when buf is not NULL in ioc_general

Nick Desaulniers
2019-03-08T21:14:25Z

On Thu, Mar 7, 2019 at 3:19 PM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> When building with -Wsometimes-uninitialized, Clang warns:
>
> drivers/scsi/gdth.c:3662:6: warning: variable 'paddr' is used
> uninitialized whenever 'if' condition is false
> [-Wsometimes-uninitialized]
>
> Don't attempt to call dma_free_coherent when buf is NULL (meaning that
> we never called dma_alloc_coherent and initialized paddr), which avoids
> this warning.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/402
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
> drivers/scsi/gdth.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/scsi/gdth.c b/drivers/scsi/gdth.c
> index e7f1dd4f3b66..0ca9b4393770 100644
> --- a/drivers/scsi/gdth.c
> +++ b/drivers/scsi/gdth.c
> @@ -3697,8 +3697,9 @@ static int ioc_general(void __user *arg, char *cmnd)
>
> rval = 0;
> out_free_buf:
> - dma_free_coherent(&ha->pdev->dev, gen.data_len + gen.sense_len, buf,
> - paddr);
> + if (buf)
> + dma_free_coherent(&ha->pdev->dev, gen.data_len + gen.sense_len,
> + buf, paddr);
> return rval;
> }
>
> --
> 2.21.0
>

Alternatively, paddr is a dma_addr_t defined in include/linux/types.h:

#ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
typedef u64 dma_addr_t;
#else
typedef u32 dma_addr_t;
#endif

Just initializing it to zero might be simpler than complicating the
control flow of this function further. Thoughts?

diff --git a/drivers/scsi/gdth.c b/drivers/scsi/gdth.c
index e7f1dd4f3b66..5a3f849ebf64 100644
--- a/drivers/scsi/gdth.c
+++ b/drivers/scsi/gdth.c
@@ -3643,7 +3643,7 @@ static int ioc_general(void __user *arg, char *cmnd)
gdth_ioctl_general gen;
gdth_ha_str *ha;
char *buf = NULL;
- dma_addr_t paddr;
+ dma_addr_t paddr = 0U;
int rval;

if (copy_from_user(&gen, arg, sizeof(gdth_ioctl_general)))
--
Thanks,
~Nick Desaulniers