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

From: Jialiang Wang
Date: Wed Aug 10 2022 - 00:08:24 EST


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