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 <[e-mail]>
Reviewed-by: Yinjun Zhang <[e-mail]>
Acked-by: Simon Horman <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c

···
 	}
 
 	/* 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 */
···
 		mutex_unlock(&cpp->area_cache_mutex);
 		return NULL;
 	}
+
+	cache->id = id;
 
 exit:
 	/* Adjust offset */