2021-04-26 13:46:40

by Lv Yunlong

Subject: [PATCH] habanalabs/gaudi: Fix a potential use after free in gaudi_memset_device_memory

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 <[email protected]>
---
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;
}
--
2.25.1

2021-05-08 08:36:44

by Oded Gabbay

Subject: Re: [PATCH] habanalabs/gaudi: Fix a potential use after free in gaudi_memset_device_memory

On Mon, Apr 26, 2021 at 4:44 PM Lv Yunlong <[email protected]> wrote:
>
> 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 <[email protected]>
> ---
> 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;
> }
> --
> 2.25.1
>
>
Reviewed-by: Oded Gabbay <[email protected]>

Thanks for catching this.
Applied to -fixes.
Oded