Re: [BUG] fs: f2fs: Possible null-pointer dereferences in update_general_status()

[Chao Yu]

Hi Jiaju,

Thanks for the report, I checked the code, and found it doesn't need to check
SM_I(sbi) pointer, this is because in fill_super() and put_super(), we will call
f2fs_destroy_stats() in prior to f2fs_destroy_segment_manager(), so if current
sbi can still be visited in global stat list, SM_I(sbi) should be released yet.
So anyway, let's remove unneeded check in line 70/78. :)

Thanks,

On 2019/7/25 17:49, Jia-Ju Bai wrote:
> In update_general_status(), there are two if statements to
> check whether SM_I(sbi) is NULL:
> LINE 70:ÂÂÂÂ if (SM_I(sbi) && SM_I(sbi)->fcc_info)
> LINE 78:ÂÂÂÂ if (SM_I(sbi) && SM_I(sbi)->dcc_info)
> 
> When SM_I(sbi) is NULL, it is used at some places, such as:
> LINE 88: reserved_segments(sbi)
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return SM_I(sbi)->reserved_segments;
> LINE 89: overprovision_segments(sbi)
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return SM_I(sbi)->ovp_segments;
> LINE 112: MAIN_SEGS(sbi)
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ (SM_I(sbi)->main_segments)
> 
> Thus, possible null-pointer dereferences may occur.
> 
> These bugs are found by a static analysis tool STCheck written by us.
> 
> I do not know how to correctly fix these bugs, so I only report them.
> 
> 
> Best wishes,
> Jia-Ju Bai
> .
>