CVE-2024-26725: In the Linux kernel, the following vulnerability has been resolved:  dpll: fix possible deadlock during netlink dump operation  Recently, I've been hitting following deadlock warning during dpll pin dump:  [52804.637962] ====================================================== [52804.638536] WARNING: possible circular locking dependency detected [52804.639111] 6.8.0-rc2jiri+ #1 Not tainted [52804.639529] ------------------------------------------------------ [52804.640104] python3/2984 is trying to acquire lock: [52804.640581] ffff88810e642678 (nlk_cb_mutex-GENERIC){+.+.}-{3:3}, at: netlink_dump+0xb3/0x780 [52804.641417]                but task is already holding lock: [52804.642010] ffffffff83bde4c8 (dpll_lock){+.+.}-{3:3}, at: dpll_lock_dumpit+0x13/0x20 [52804.642747]                which lock already depends on the new lock.  [52804.643551]                the existing dependency chain (in reverse order) is: [52804.644259]                -> #1 (dpll_lock){+.+.}-{3:3}: [52804.644836]        lock_acquire+0x174/0x3e0 [52804.645271]        __mutex_lock+0x119/0x1150 [52804.645723]        dpll_lock_dumpit+0x13/0x20 [52804.646169]        genl_start+0x266/0x320 [52804.646578]        __netlink_dump_start+0x321/0x450 [52804.647056]        genl_family_rcv_msg_dumpit+0x155/0x1e0 [52804.647575]        genl_rcv_msg+0x1ed/0x3b0 [52804.648001]        netlink_rcv_skb+0xdc/0x210 [52804.648440]        genl_rcv+0x24/0x40 [52804.648831]        netlink_unicast+0x2f1/0x490 [52804.649290]        netlink_sendmsg+0x36d/0x660 [52804.649742]        __sock_sendmsg+0x73/0xc0 [52804.650165]        __sys_sendto+0x184/0x210 [52804.650597]        __x64_sys_sendto+0x72/0x80 [52804.651045]        do_syscall_64+0x6f/0x140 [52804.651474]        entry_SYSCALL_64_after_hwframe+0x46/0x4e [52804.652001]                -> #0 (nlk_cb_mutex-GENERIC){+.+.}-{3:3}: [52804.652650]        check_prev_add+0x1ae/0x1280 [52804.653107]        __lock_acquire+0x1ed3/0x29a0 [52804.653559]        lock_acquire+0x174/0x3e0 [52804.653984]        __mutex_lock+0x119/0x1150 [52804.654423]        netlink_dump+0xb3/0x780 [52804.654845]        __netlink_dump_start+0x389/0x450 [52804.655321]        genl_family_rcv_msg_dumpit+0x155/0x1e0 [52804.655842]        genl_rcv_msg+0x1ed/0x3b0 [52804.656272]        netlink_rcv_skb+0xdc/0x210 [52804.656721]        genl_rcv+0x24/0x40 [52804.657119]        netlink_unicast+0x2f1/0x490 [52804.657570]        netlink_sendmsg+0x36d/0x660 [52804.658022]        __sock_sendmsg+0x73/0xc0 [52804.658450]        __sys_sendto+0x184/0x210 [52804.658877]        __x64_sys_sendto+0x72/0x80 [52804.659322]        do_syscall_64+0x6f/0x140 [52804.659752]        entry_SYSCALL_64_after_hwframe+0x46/0x4e [52804.660281]                other info that might help us debug this:  [52804.661077]  Possible unsafe locking scenario:  [52804.661671]        CPU0                    CPU1 [52804.662129]        ----                    ---- [52804.662577]   lock(dpll_lock); [52804.662924]                                lock(nlk_cb_mutex-GENERIC); [52804.663538]                                lock(dpll_lock); [52804.664073]   lock(nlk_cb_mutex-GENERIC); [52804.664490]  The issue as follows: __netlink_dump_start() calls control->start(cb) with nlk->cb_mutex held. In control->start(cb) the dpll_lock is taken. Then nlk->cb_mutex is released and taken again in netlink_dump(), while dpll_lock still being held. That leads to ABBA deadlock when another CPU races with the same operation.  Fix this by moving dpll_lock taking into dumpit() callback which ensures correct lock taking order.