linux-kernel - Re: [PATCH] dma-buf: st: fix error handling in test_get

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Date:   Tue, 26 Oct 2021 07:04:00 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...el.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Arnd Bergmann <arnd@...db.de>, linux-media@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] dma-buf: st: fix error handling in test_get_fences()

On Tue, Oct 26, 2021 at 10:34:37AM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> The new driver incorrectly unwinds after errors, as clang points out:
> 
> drivers/dma-buf/st-dma-resv.c:295:7: error: variable 'i' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
>                 if (r) {
>                     ^
> drivers/dma-buf/st-dma-resv.c:336:9: note: uninitialized use occurs here
>         while (i--)
>                ^
> drivers/dma-buf/st-dma-resv.c:295:3: note: remove the 'if' if its condition is always false
>                 if (r) {
>                 ^~~~~~~~
> drivers/dma-buf/st-dma-resv.c:288:6: error: variable 'i' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
>         if (r) {
>             ^
> drivers/dma-buf/st-dma-resv.c:336:9: note: uninitialized use occurs here
>         while (i--)
>                ^
> drivers/dma-buf/st-dma-resv.c:288:2: note: remove the 'if' if its condition is always false
>         if (r) {
>         ^~~~~~~~
> drivers/dma-buf/st-dma-resv.c:280:10: note: initialize the variable 'i' to silence this warning
>         int r, i;
>                 ^
>                  = 0
> 
> Skip cleaning up the bits that have not been allocated at this point.
> 
> Fixes: 1d51775cd3f5 ("dma-buf: add dma_resv selftest v4")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Reviewed-by: Nathan Chancellor <nathan@...nel.org>

> ---
> I'm not familiar with these interfaces, so I'm just guessing where
> we should jump after an error, please double-check and fix if necessary.
> ---
>  drivers/dma-buf/st-dma-resv.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma-buf/st-dma-resv.c b/drivers/dma-buf/st-dma-resv.c
> index 6f3ba756da3e..bc32b3eedcb6 100644
> --- a/drivers/dma-buf/st-dma-resv.c
> +++ b/drivers/dma-buf/st-dma-resv.c
> @@ -287,7 +287,7 @@ static int test_get_fences(void *arg, bool shared)
>  	r = dma_resv_lock(&resv, NULL);
>  	if (r) {
>  		pr_err("Resv locking failed\n");
> -		goto err_free;
> +		goto err_resv;
>  	}
>  
>  	if (shared) {
> @@ -295,7 +295,7 @@ static int test_get_fences(void *arg, bool shared)
>  		if (r) {
>  			pr_err("Resv shared slot allocation failed\n");
>  			dma_resv_unlock(&resv);
> -			goto err_free;
> +			goto err_resv;
>  		}
>  
>  		dma_resv_add_shared_fence(&resv, f);
> @@ -336,6 +336,7 @@ static int test_get_fences(void *arg, bool shared)
>  	while (i--)
>  		dma_fence_put(fences[i]);
>  	kfree(fences);
> +err_resv:
>  	dma_resv_fini(&resv);
>  	dma_fence_put(f);
>  	return r;
> -- 
> 2.29.2
>