Re: [PATCH] nfp: fix use-after-free in area_cache_get()

[Jakub Kicinski <kuba@kernel.org>]

On Sat,  6 Aug 2022 22:30:43 +0800 Jialiang Wang wrote:
> area_cache_get() calls cpp->op->area_init() and uses cache->area by
>  nfp_cpp_area_priv(area), but in
>  nfp_cpp_area_release()->nfp_cpp_area_put()->__release_cpp_area() we
>  already freed the cache->area.
> 
> To avoid the use-after-free, reallocate a piece of memory for the
>  cache->area by nfp_cpp_area_alloc().
> 
> Note: This vulnerability is triggerable by providing emulated device
>  equipped with specified configuration.
> 
> BUG: KASAN: use-after-free in nfp6000_area_init+0x74/0x1d0 [nfp]
> Write of size 4 at addr ffff888005b490a0 by task insmod/226
> Call Trace:
>   <TASK>
>   dump_stack_lvl+0x33/0x46
>   print_report.cold.12+0xb2/0x6b7
>   ? nfp6000_area_init+0x74/0x1d0 [nfp]
>   kasan_report+0xa5/0x120
>   ? nfp6000_area_init+0x74/0x1d0 [nfp]
>   nfp6000_area_init+0x74/0x1d0 [nfp]
>   area_cache_get.constprop.8+0x2da/0x360 [nfp]

Please provide more of the report, including the allocated at and freed
at sections and run the thing thru stack decode so we get the line
numbers.