linux-kernel - RE: [PATCH] drm/amdgpu: Fix realloc of ptr

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Date:   Sat, 26 Feb 2022 22:21:58 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     "'trix@...hat.com'" <trix@...hat.com>,
        "alexander.deucher@....com" <alexander.deucher@....com>,
        "christian.koenig@....com" <christian.koenig@....com>,
        "Xinhui.Pan@....com" <Xinhui.Pan@....com>,
        "airlied@...ux.ie" <airlied@...ux.ie>,
        "daniel@...ll.ch" <daniel@...ll.ch>,
        "nathan@...nel.org" <nathan@...nel.org>,
        "ndesaulniers@...gle.com" <ndesaulniers@...gle.com>,
        "nirmoy.das@....com" <nirmoy.das@....com>,
        "lijo.lazar@....com" <lijo.lazar@....com>,
        "tom.stdenis@....com" <tom.stdenis@....com>,
        "evan.quan@....com" <evan.quan@....com>,
        "kevin1.wang@....com" <kevin1.wang@....com>,
        "Amaranath.Somalapuram@....com" <Amaranath.Somalapuram@....com>
CC:     "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "llvm@...ts.linux.dev" <llvm@...ts.linux.dev>
Subject: RE: [PATCH] drm/amdgpu: Fix realloc of ptr

From: trix@...hat.com
> Sent: 26 February 2022 15:59
> 
> From: Tom Rix <trix@...hat.com>
> 
> Clang static analysis reports this error
> amdgpu_debugfs.c:1690:9: warning: 1st function call
>   argument is an uninitialized value
>   tmp = krealloc_array(tmp, i + 1,
>         ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> realloc will free tmp, so tmp can not be garbage.
> And the return needs to be checked.

Are you sure?
A quick check seems to show that krealloc() behaves the same
way as libc realloc() and the pointer isn't freed on failure.

	David

> Fixes: 5ce5a584cb82 ("drm/amdgpu: add debugfs for reset registers list")
> Signed-off-by: Tom Rix <trix@...hat.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> index 9eb9b440bd438..159b97c0b4ebc 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> @@ -1676,7 +1676,7 @@ static ssize_t amdgpu_reset_dump_register_list_write(struct file *f,
>  {
>  	struct amdgpu_device *adev = (struct amdgpu_device *)file_inode(f)->i_private;
>  	char reg_offset[11];
> -	uint32_t *tmp;
> +	uint32_t *tmp = NULL;
>  	int ret, i = 0, len = 0;
> 
>  	do {
> @@ -1688,6 +1688,10 @@ static ssize_t amdgpu_reset_dump_register_list_write(struct file *f,
>  		}
> 
>  		tmp = krealloc_array(tmp, i + 1, sizeof(uint32_t), GFP_KERNEL);
> +		if (!tmp) {
> +			ret = -ENOMEM;
> +			goto error_free;
> +		}
>  		if (sscanf(reg_offset, "%X %n", &tmp[i], &ret) != 1) {
>  			ret = -EINVAL;
>  			goto error_free;
> --
> 2.26.3

-
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