[PATCH v2] nfp: fix use-after-free in area_cache_get()

[Jialiang Wang]

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 <wangjialiang0806@xxxxxxx>
---
 drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c
index 34c0d2ddf9ef..a83b8ee49062 100644
--- a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c
+++ b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c
@@ -873,10 +873,6 @@ area_cache_get(struct nfp_cpp *cpp, u32 id,
 		cache->addr = 0;
 	}
 
-	/* 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 */
 	if (cpp->op->area_init) {
 		err = cpp->op->area_init(cache->area,
@@ -894,6 +890,10 @@ area_cache_get(struct nfp_cpp *cpp, u32 id,
 		return NULL;
 	}
 
+	/* Adjust the start address to be cache size aligned */
+	cache->id = id;
+	cache->addr = addr & ~(u64)(cache->size - 1);
+
 exit:
 	/* Adjust offset */
 	*offset = addr - cache->addr;
-- 
2.17.1