linux-kernel - [PATCH] nfp: fix use-after-free in area_cache

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Date:   Sat,  6 Aug 2022 22:30:43 +0800
From:   Jialiang Wang <wangjialiang0806@....com>
To:     simon.horman@...igine.com, kuba@...nel.org, davem@...emloft.net,
        edumazet@...gle.com, pabeni@...hat.com, niejianglei2021@....com,
        wangjialiang0806@....com
Cc:     oss-drivers@...igine.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] nfp: fix use-after-free in area_cache_get()

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]

Signed-off-by: Jialiang Wang <wangjialiang0806@....com>
---
 drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c
index 34c0d2ddf9ef..99091f24d2ba 100644
--- a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c
+++ b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c
@@ -871,6 +871,10 @@ area_cache_get(struct nfp_cpp *cpp, u32 id,
 		nfp_cpp_area_release(cache->area);
 		cache->id = 0;
 		cache->addr = 0;
+		cache->area = nfp_cpp_area_alloc(cpp,
+						 NFP_CPP_ID(7,
+						 NFP_CPP_ACTION_RW, 0),
+						 0, cache->size);
 	}

 	/* Adjust the start address to be cache size aligned */
-- 
2.17.1