CVE-2025-21744

In the Linux kernel, the following vulnerability has been resolved:

wifi: brcmfmac: fix NULL pointer dereference in brcmf_txfinalize()

On removal of the device or unloading of the kernel module a potential NULL

pointer dereference occurs.

The following sequence deletes the interface:

brcmf_detach()

brcmf_remove_interface()

brcmf_del_if()

Inside the brcmf_del_if() function the drvr->if2bss[ifidx] is updated to

BRCMF_BSSIDX_INVALID (-1) if the bsscfgidx matches.

After brcmf_remove_interface() call the brcmf_proto_detach() function is

called providing the following sequence:

brcmf_detach()

brcmf_proto_detach()

brcmf_proto_msgbuf_detach()

brcmf_flowring_detach()

brcmf_msgbuf_delete_flowring()

brcmf_msgbuf_remove_flowring()

brcmf_flowring_delete()

brcmf_get_ifp()

brcmf_txfinalize()

Since brcmf_get_ip() can and actually will return NULL in this case the

call to brcmf_txfinalize() will result in a NULL pointer dereference inside

brcmf_txfinalize() when trying to update ifp->ndev->stats.tx_errors.

This will only happen if a flowring still has an skb.

Although the NULL pointer dereference has only been seen when trying to

update the tx statistic, all other uses of the ifp pointer have been

guarded as well with an early return if ifp is NULL.