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From: Santosh Sivaraj <santosh@fossix.org>
To: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>, robh@kernel.org,
 dan.carpenter@oracle.com, mpe@ellerman.id.au
Subject: Re: [PATCH 1/2] powerpc: Free fdt on error in elf64_load()
In-Reply-To: <20210420190355.10059-1-nramas@linux.microsoft.com>
References: <20210420190355.10059-1-nramas@linux.microsoft.com>
Date: Wed, 21 Apr 2021 11:05:17 +0530
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Hi Lakshmi,

Lakshmi Ramasubramanian <nramas@linux.microsoft.com> writes:

> There are a few "goto out;" statements before the local variable "fdt"
> is initialized through the call to of_kexec_alloc_and_setup_fdt() in
> elf64_load().  This will result in an uninitialized "fdt" being passed
> to kvfree() in this function if there is an error before the call to
> of_kexec_alloc_and_setup_fdt().
>
> If there is any error after fdt is allocated, but before it is
> saved in the arch specific kimage struct, free the fdt.
>
> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
> ---
>  arch/powerpc/kexec/elf_64.c | 16 ++++++----------
>  1 file changed, 6 insertions(+), 10 deletions(-)
>
> diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
> index 5a569bb51349..02662e72c53d 100644
> --- a/arch/powerpc/kexec/elf_64.c
> +++ b/arch/powerpc/kexec/elf_64.c
> @@ -114,7 +114,7 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
>  	ret = setup_new_fdt_ppc64(image, fdt, initrd_load_addr,
>  				  initrd_len, cmdline);
>  	if (ret)
> -		goto out;
> +		goto out_free_fdt;

Shouldn't there be a goto out_free_fdt if fdt_open_into fails?

>  
>  	fdt_pack(fdt);
>  
> @@ -125,7 +125,7 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
>  	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
>  	ret = kexec_add_buffer(&kbuf);
>  	if (ret)
> -		goto out;
> +		goto out_free_fdt;
>  
>  	/* FDT will be freed in arch_kimage_file_post_load_cleanup */
>  	image->arch.fdt = fdt;
> @@ -140,18 +140,14 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
>  	if (ret)
>  		pr_err("Error setting up the purgatory.\n");
>  
> +	goto out;
> +
> +out_free_fdt:
> +	kvfree(fdt);

Can just use kfree here?

Thanks,
Santosh
>  out:
>  	kfree(modified_cmdline);
>  	kexec_free_elf_info(&elf_info);
>  
> -	/*
> -	 * Once FDT buffer has been successfully passed to kexec_add_buffer(),
> -	 * the FDT buffer address is saved in image->arch.fdt. In that case,
> -	 * the memory cannot be freed here in case of any other error.
> -	 */
> -	if (ret && !image->arch.fdt)
> -		kvfree(fdt);
> -
>  	return ret ? ERR_PTR(ret) : NULL;
>  }
>  
> -- 
> 2.31.0