Subject: Re: [PATCH v3] nfp: fix use-after-free in area_cache_get()

From: Lee Jones <[email-masked]>
Date: Wed, 7 Dec 2022 12:21:10 +0000

On Wed, 10 Aug 2022, Jialiang Wang wrote:

> area_cache_get() is used to distribute cache->area and set cache->id,
>  and if cache->id is not 0 and cache->area->kref refcount is 0, it will
>  release the cache->area by nfp_cpp_area_release(). area_cache_get()
>  set cache->id before cpp->op->area_init() and nfp_cpp_area_acquire().
> 
> But if area_init() or nfp_cpp_area_acquire() fails, the cache->id is
>  is already set but the refcount is not increased as expected. At this
>  time, calling the nfp_cpp_area_release() will cause use-after-free.
> 
> To avoid the use-after-free, set cache->id after area_init() and
>  nfp_cpp_area_acquire() complete successfully.
> 
> Note: This vulnerability is triggerable by providing emulated device
>  equipped with specified configuration.
> 
>  BUG: KASAN: use-after-free in nfp6000_area_init (/home/user/Kernel/v5.19
> /x86_64/src/drivers/net/ethernet/netronome/nfp/nfpcore/nfp6000_pcie.c:760)
>   Write of size 4 at addr ffff888005b7f4a0 by task swapper/0/1
> 
>  Call Trace:
>   <TASK>
>  nfp6000_area_init (/home/user/Kernel/v5.19/x86_64/src/drivers/net
> /ethernet/netronome/nfp/nfpcore/nfp6000_pcie.c:760)
>  area_cache_get.constprop.8 (/home/user/Kernel/v5.19/x86_64/src/drivers
> /net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:884)
> 
>  Allocated by task 1:
>  nfp_cpp_area_alloc_with_name (/home/user/Kernel/v5.19/x86_64/src/drivers
> /net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:303)
>  nfp_cpp_area_cache_add (/home/user/Kernel/v5.19/x86_64/src/drivers/net
> /ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:802)
>  nfp6000_init (/home/user/Kernel/v5.19/x86_64/src/drivers/net/ethernet
> /netronome/nfp/nfpcore/nfp6000_pcie.c:1230)
>  nfp_cpp_from_operations (/home/user/Kernel/v5.19/x86_64/src/drivers/net
> /ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:1215)
>  nfp_pci_probe (/home/user/Kernel/v5.19/x86_64/src/drivers/net/ethernet
> /netronome/nfp/nfp_main.c:744)
> 
>  Freed by task 1:
>  kfree (/home/user/Kernel/v5.19/x86_64/src/mm/slub.c:4562)
>  area_cache_get.constprop.8 (/home/user/Kernel/v5.19/x86_64/src/drivers
> /net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:873)
>  nfp_cpp_read (/home/user/Kernel/v5.19/x86_64/src/drivers/net/ethernet
> /netronome/nfp/nfpcore/nfp_cppcore.c:924 /home/user/Kernel/v5.19/x86_64
> /src/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:973)
>  nfp_cpp_readl (/home/user/Kernel/v5.19/x86_64/src/drivers/net/ethernet
> /netronome/nfp/nfpcore/nfp_cpplib.c:48)
> 
> Signed-off-by: Jialiang Wang <[email-masked]>

Any reason why this doesn't have a Fixes: tag applied and/or didn't
get sent to Stable?

Looks as if this needs to go back as far as v4.19.

Fixes: 4cb584e0ee7df ("nfp: add CPP access core")

commit 02e1a114fdb71e59ee6770294166c30d437bf86a upstream.

> ---
>  drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c
> index 34c0d2ddf9ef..a8286d0032d1 100644
> --- a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c
> +++ b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c
> @@ -874,7 +874,6 @@ area_cache_get(struct nfp_cpp *cpp, u32 id,
>  	}
>  
>  	/* Adjust the start address to be cache size aligned */
> -	cache->id = id;
>  	cache->addr = addr & ~(u64)(cache->size - 1);
>  
>  	/* Re-init to the new ID and address */
> @@ -894,6 +893,8 @@ area_cache_get(struct nfp_cpp *cpp, u32 id,
>  		return NULL;
>  	}
>  
> +	cache->id = id;
> +
>  exit:
>  	/* Adjust offset */
>  	*offset = addr - cache->addr;

-- 
Lee Jones [李琼斯]