Re: [PATCH 1/2] powerpc: Free fdt on error in elf64_load()

[Santosh Sivaraj <santosh@fossix.org>]

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

> On 4/20/21 10:35 PM, Santosh Sivaraj wrote:
> Hi Santosh,
>
>> 
>>> 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?
>
> You are likely looking at elf_64.c in the mainline branch. The patch I 
> have submitted is based on Rob's device-tree for-next branch. Please see 
> the link below:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git/tree/arch/powerpc/kexec/elf_64.c?h=for-next

That's right, I was indeed looking at the mainline. Sorry for the noise.

Thanks,
Santosh

>
>> 
>>>   
>>>   	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?
> "fdt" is allocated through kvmalloc(). So it is freed using kvfree.
>
> thanks,
>   -lakshmi
>
>>>   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