[PATCH 0/4] staging: rtl8723bs: fix several memory-safety bugs

[PATCH 0/4] staging: rtl8723bs: fix several memory-safety bugs

[Yi Cong]

From: Yi Cong <yicong@kylinos.cn>

This small series fixes four memory-safety / resource-management bugs in
the rtl8723bs SDIO staging driver.

All four are tagged:

  Fixes: 554c0a3abf21 ("staging: Add rtl8723bs sdio wifi driver")

  1/4 - kfree() used on a vzalloc() allocation (HalData) in the probe
        error path.
  2/4 - double free / UAF when register_netdev() fails: the error label
        frees objects that the caller also frees.
  3/4 - NULL deref in c2h_wk_callback() when the re-read allocation under
        memory pressure fails.
  4/4 - NULL deref on a bcmc station lookup in the 802.11 defrag path,
        reachable from a fragment with an unknown transmitter address.

Yi Cong (4):
  staging: rtl8723bs: free HalData with vfree, not kfree
  staging: rtl8723bs: fix double free when register_netdev() fails
  staging: rtl8723bs: fix NULL deref in c2h_wk_callback() on alloc
    failure
  staging: rtl8723bs: fix NULL deref on bcmc station lookup in defrag
    path

 drivers/staging/rtl8723bs/core/rtw_cmd.c     |  6 ++++++
 drivers/staging/rtl8723bs/core/rtw_recv.c    |  5 ++++-
 drivers/staging/rtl8723bs/os_dep/os_intfs.c  | 10 ++++++----
 drivers/staging/rtl8723bs/os_dep/sdio_intf.c |  2 +-
 4 files changed, 17 insertions(+), 6 deletions(-)

-- 
2.25.1

[PATCH 1/4] staging: rtl8723bs: free HalData with vfree, not kfree

[Yi Cong]

From: Yi Cong <yicong@kylinos.cn>

In the probe error path of rtw_sdio_if1_init(), HalData is released with
kfree(), but it is allocated with vzalloc() in rtw_hal_data_init(). Freeing
a vmalloc allocation with kfree() is undefined behaviour and can corrupt
the allocator.

Use rtw_hal_data_deinit() instead, which calls vfree() and is the matching
deallocator used on the normal tear-down path. It also NULLs the pointer
and clears hal_data_sz, making it safe to call here.

Fixes: 554c0a3abf21 ("staging: Add rtl8723bs sdio wifi driver")
Signed-off-by: Yi Cong <yicong@kylinos.cn>
---
 drivers/staging/rtl8723bs/os_dep/sdio_intf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/rtl8723bs/os_dep/sdio_intf.c b/drivers/staging/rtl8723bs/os_dep/sdio_intf.c
index c43a0391a5ca..f7ec09310ce9 100644
--- a/drivers/staging/rtl8723bs/os_dep/sdio_intf.c
+++ b/drivers/staging/rtl8723bs/os_dep/sdio_intf.c
@@ -286,7 +286,7 @@ static struct adapter *rtw_sdio_if1_init(struct dvobj_priv *dvobj, const struct
 
 free_hal_data:
 	if (status != _SUCCESS && padapter->HalData)
-		kfree(padapter->HalData);
+		rtw_hal_data_deinit(padapter);
 
 	if (status != _SUCCESS) {
 		rtw_wdev_unregister(padapter->rtw_wdev);
-- 
2.25.1

[PATCH 2/4] staging: rtl8723bs: fix double free when register_netdev() fails

[Yi Cong]

From: Yi Cong <yicong@kylinos.cn>

When register_netdev() fails, the error_register_netdev label in
_rtw_drv_register_netdev() frees the adapter and netdev via
rtw_free_drv_sw()/rtw_free_netdev() and then returns _FAIL.

The caller rtw_drv_init(), however, still holds a non-NULL if1 on this
failure path and jumps to free_if1, where rtw_sdio_if1_deinit() invokes
rtw_free_drv_sw() and rtw_free_netdev() again on the same already-freed
objects, resulting in a double free / use-after-free.

Drop the freeing from error_register_netdev and let rtw_sdio_if1_deinit()
perform the tear-down, which is the single owner for this path.

Fixes: 554c0a3abf21 ("staging: Add rtl8723bs sdio wifi driver")
Signed-off-by: Yi Cong <yicong@kylinos.cn>
---
 drivers/staging/rtl8723bs/os_dep/os_intfs.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/rtl8723bs/os_dep/os_intfs.c b/drivers/staging/rtl8723bs/os_dep/os_intfs.c
index f31196f54b3e..ac401042faf4 100644
--- a/drivers/staging/rtl8723bs/os_dep/os_intfs.c
+++ b/drivers/staging/rtl8723bs/os_dep/os_intfs.c
@@ -773,10 +773,12 @@ static int _rtw_drv_register_netdev(struct adapter *padapter, char *name)
 
 error_register_netdev:
 
-	rtw_free_drv_sw(padapter);
-
-	rtw_free_netdev(pnetdev);
-
+	/* Let the caller (rtw_drv_init -> rtw_sdio_if1_deinit) release the
+	 * adapter and netdev. Freeing them here would lead to a double free:
+	 * rtw_drv_init() still holds a non-NULL if1 and calls
+	 * rtw_sdio_if1_deinit(), which invokes rtw_free_drv_sw() and
+	 * rtw_free_netdev() again on the already-freed objects.
+	 */
 	return ret;
 }
 
-- 
2.25.1

[PATCH 3/4] staging: rtl8723bs: fix NULL deref in c2h_wk_callback() on alloc failure

[Yi Cong]

From: Yi Cong <yicong@kylinos.cn>

When the SDIO interrupt handler cannot allocate a c2h event buffer
(GFP_ATOMIC under memory pressure) it pushes NULL onto c2h_queue as a
"needs re-read" marker and wakes c2h_wk. In c2h_wk_callback(), if the
re-allocation also fails, c2h_evt stays NULL and execution falls through
to rtw_hal_c2h_valid(adapter, c2h_evt), whose underlying macro dereferences
c2h_evt->id, causing a NULL pointer dereference panic.

C2H interrupts are produced by firmware/network events at runtime, so this
is reachable under memory pressure. Add a `continue` in the re-allocation
failure branch to give up this event instead of dereferencing NULL.

Fixes: 554c0a3abf21 ("staging: Add rtl8723bs sdio wifi driver")
Signed-off-by: Yi Cong <yicong@kylinos.cn>
---
 drivers/staging/rtl8723bs/core/rtw_cmd.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/staging/rtl8723bs/core/rtw_cmd.c b/drivers/staging/rtl8723bs/core/rtw_cmd.c
index b932670f5d63..8dc700b9f2e9 100644
--- a/drivers/staging/rtl8723bs/core/rtw_cmd.c
+++ b/drivers/staging/rtl8723bs/core/rtw_cmd.c
@@ -1716,6 +1716,12 @@ static void c2h_wk_callback(struct work_struct *work)
 					kfree(c2h_evt);
 					continue;
 				}
+			} else {
+				/* Give up this event; re-allocation failed. Falling
+				 * through would dereference the NULL c2h_evt in
+				 * rtw_hal_c2h_valid() below.
+				 */
+				continue;
 			}
 		}
 
-- 
2.25.1

[PATCH 4/4] staging: rtl8723bs: fix NULL deref on bcmc station lookup in defrag path

[Yi Cong]

From: Yi Cong <yicong@kylinos.cn>

In recvframe_chk_defrag(), when a fragment's transmitter address is unknown
(no associated station) and the frame is not a data frame, the code looks
up the broadcast/multicast station with rtw_get_bcmc_stainfo() and
immediately dereferences the result to obtain defrag_q, without a NULL
check. rtw_get_bcmc_stainfo() (a thin wrapper around rtw_get_stainfo())
can return NULL, for example if the bcmc station has not been or is no
longer allocated.

Every other call site of rtw_get_bcmc_stainfo() in the driver checks the
return value; this one was missed. A fragment with an unknown transmitter
address received from the network (e.g. an injected/rogue management
fragment) could thus trigger a NULL pointer dereference panic.

Check the return value and set pdefrag_q = NULL when no bcmc station is
available, consistent with the adjacent data-frame branch (the later code
already handles pdefrag_q == NULL).

Fixes: 554c0a3abf21 ("staging: Add rtl8723bs sdio wifi driver")
Signed-off-by: Yi Cong <yicong@kylinos.cn>
---
 drivers/staging/rtl8723bs/core/rtw_recv.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/rtl8723bs/core/rtw_recv.c b/drivers/staging/rtl8723bs/core/rtw_recv.c
index 86c5e2c4e7dd..ffcee431caf5 100644
--- a/drivers/staging/rtl8723bs/core/rtw_recv.c
+++ b/drivers/staging/rtl8723bs/core/rtw_recv.c
@@ -1146,7 +1146,10 @@ static union recv_frame *recvframe_chk_defrag(struct adapter *padapter, union re
 
 		if (type != WIFI_DATA_TYPE) {
 			psta = rtw_get_bcmc_stainfo(padapter);
-			pdefrag_q = &psta->sta_recvpriv.defrag_q;
+			if (psta)
+				pdefrag_q = &psta->sta_recvpriv.defrag_q;
+			else
+				pdefrag_q = NULL;
 		} else {
 			pdefrag_q = NULL;
 		}
-- 
2.25.1

Re: [PATCH 2/4] staging: rtl8723bs: fix double free when register_netdev() fails

[Dan Carpenter]

On Wed, Jul 29, 2026 at 10:25:07AM +0800, Yi Cong wrote:
> From: Yi Cong <yicong@kylinos.cn>
> 
> When register_netdev() fails, the error_register_netdev label in
> _rtw_drv_register_netdev() frees the adapter and netdev via
> rtw_free_drv_sw()/rtw_free_netdev() and then returns _FAIL.
> 
> The caller rtw_drv_init(), however, still holds a non-NULL if1 on this
> failure path and jumps to free_if1, where rtw_sdio_if1_deinit() invokes
> rtw_free_drv_sw() and rtw_free_netdev() again on the same already-freed
> objects, resulting in a double free / use-after-free.
> 
> Drop the freeing from error_register_netdev and let rtw_sdio_if1_deinit()
> perform the tear-down, which is the single owner for this path.
> 
> Fixes: 554c0a3abf21 ("staging: Add rtl8723bs sdio wifi driver")
> Signed-off-by: Yi Cong <yicong@kylinos.cn>
> ---
>  drivers/staging/rtl8723bs/os_dep/os_intfs.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/staging/rtl8723bs/os_dep/os_intfs.c b/drivers/staging/rtl8723bs/os_dep/os_intfs.c
> index f31196f54b3e..ac401042faf4 100644
> --- a/drivers/staging/rtl8723bs/os_dep/os_intfs.c
> +++ b/drivers/staging/rtl8723bs/os_dep/os_intfs.c
> @@ -773,10 +773,12 @@ static int _rtw_drv_register_netdev(struct adapter *padapter, char *name)
>  
>  error_register_netdev:
>  
> -	rtw_free_drv_sw(padapter);
> -
> -	rtw_free_netdev(pnetdev);
> -
> +	/* Let the caller (rtw_drv_init -> rtw_sdio_if1_deinit) release the
> +	 * adapter and netdev. Freeing them here would lead to a double free:
> +	 * rtw_drv_init() still holds a non-NULL if1 and calls
> +	 * rtw_sdio_if1_deinit(), which invokes rtw_free_drv_sw() and
> +	 * rtw_free_netdev() again on the already-freed objects.
> +	 */

No need for this comment.  These weren't allocated in
_rtw_drv_register_netdev() and no one really expects them to be
freed here either.  AI always adds obvious comments but eventually
the kernel will turn into the Terms of Service text which no one can
possibly read in a life time.

regards,
dan carpenter