CVE-2024-26725: In the Linux kernel, the following vulnerability has been resolved:dpll: fix possible deadlock during netlink dump operationRecently, I've been hitting following deadlock warning during dpll pindump:[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(), whiledpll_lock still being held. That leads to ABBA deadlock when anotherCPU races with the same operation.Fix this by moving dpll_lock taking into dumpit() callback which ensurescorrect lock taking order.