[PATCH 5.12 004/127] habanalabs/gaudi: Fix a potential use after free in gaudi_memset_device_memory

Greg Kroah-Hartman
2021-05-24T16:04:26Z

From: Lv Yunlong <lyl2019@mail.ustc.edu.cn>

[ Upstream commit 115726c5d312b462c9d9931ea42becdfa838a076 ]

Our code analyzer reported a uaf.

In gaudi_memset_device_memory, cb is get via hl_cb_kernel_create()
with 2 refcount.
If hl_cs_allocate_job() failed, the execution runs into release_cb
branch. One ref of cb is dropped by hl_cb_put(cb) and could be freed
if other thread also drops one ref. Then cb is used by cb->id later,
which is a potential uaf.

My patch add a variable 'id' to accept the value of cb->id before the
hl_cb_put(cb) is called, to avoid the potential uaf.

Fixes: 423815bf02e25 ("habanalabs/gaudi: remove PCI access to SM block")
Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/misc/habanalabs/gaudi/gaudi.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/habanalabs/gaudi/gaudi.c b/drivers/misc/habanalabs/gaudi/gaudi.c
index 9152242778f5..ecdedd87f8cc 100644
--- a/drivers/misc/habanalabs/gaudi/gaudi.c
+++ b/drivers/misc/habanalabs/gaudi/gaudi.c
@@ -5546,6 +5546,7 @@ static int gaudi_memset_device_memory(struct hl_device *hdev, u64 addr,
struct hl_cs_job *job;
u32 cb_size, ctl, err_cause;
struct hl_cb *cb;
+ u64 id;
int rc;

cb = hl_cb_kernel_create(hdev, PAGE_SIZE, false);
@@ -5612,8 +5613,9 @@ static int gaudi_memset_device_memory(struct hl_device *hdev, u64 addr,
}

release_cb:
+ id = cb->id;
hl_cb_put(cb);
- hl_cb_destroy(hdev, &hdev->kernel_cb_mgr, cb->id << PAGE_SHIFT);
+ hl_cb_destroy(hdev, &hdev->kernel_cb_mgr, id << PAGE_SHIFT);

return rc;
}
--
2.30.2