nfp: fix use-after-free in area_cache_get()

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 (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 (drivers/net/ethernet/netronome/nfp/nfpcore/nfp6000_pcie.c:760)
 area_cache_get.constprop.8 (drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:884)

 Allocated by task 1:
 nfp_cpp_area_alloc_with_name (drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:303)
 nfp_cpp_area_cache_add (drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:802)
 nfp6000_init (drivers/net/ethernet/netronome/nfp/nfpcore/nfp6000_pcie.c:1230)
 nfp_cpp_from_operations (drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:1215)
 nfp_pci_probe (drivers/net/ethernet/netronome/nfp/nfp_main.c:744)

 Freed by task 1:
 kfree (mm/slub.c:4562)
 area_cache_get.constprop.8 (drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:873)
 nfp_cpp_read (drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:924 drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:973)
 nfp_cpp_readl (drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cpplib.c:48)
Signed-off-by: Jialiang Wang <wangjialiang0806@163.com>
Reviewed-by: Yinjun Zhang <yinjun.zhang@corigine.com>
Acked-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20220810073057.4032-1-wangjialiang0806@163.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

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;