Jeongjun Park 2efe41234d ptp: prevent possible ABBA deadlock in ptp_clock_freerun() ... syzbot reported the following ABBA deadlock: CPU0 CPU1 ---- ---- n_vclocks_store() lock(&ptp->n_vclocks_mux) [1] (physical clock) pc_clock_adjtime() lock(&clk->rwsem) [2] (physical clock) ... ptp_clock_freerun() ptp_vclock_in_use() lock(&ptp->n_vclocks_mux) [3] (physical clock) ptp_clock_unregister() posix_clock_unregister() lock(&clk->rwsem) [4] (virtual clock) Since ptp virtual clock is registered only under ptp physical clock, both ptp_clock and posix_clock must be physical clocks for ptp_vclock_in_use() to lock &ptp->n_vclocks_mux and check ptp->n_vclocks. However, when unregistering vclocks in n_vclocks_store(), the locking ptp->n_vclocks_mux is a physical clock lock, but clk->rwsem of ptp_clock_unregister() called through device_for_each_child_reverse() is a virtual clock lock. Therefore, clk->rwsem used in CPU0 and clk->rwsem used in CPU1 are different locks, but in lockdep, a false positive occurs because the possibility of deadlock is determined through lock-class. To solve this, lock subclass annotation must be added to the posix_clock rwsem of the vclock. Reported-by: syzbot+7cfb66a237c4a5fb22ad@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=7cfb66a237c4a5fb22ad Fixes: 73f37068d5 ("ptp: support ptp physical/virtual clocks conversion") Signed-off-by: Jeongjun Park <aha310510@gmail.com> Acked-by: Richard Cochran <richardcochran@gmail.com> Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com> Link: https://patch.msgid.link/20250728062649.469882-1-aha310510@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>		2025-08-12 14:17:35 -07:00
..
Kconfig
Makefile
ptp_chardev.c
ptp_clock.c
ptp_clockmatrix.c
ptp_clockmatrix.h
ptp_dfl_tod.c
ptp_dte.c
ptp_fc3.c
ptp_fc3.h
ptp_idt82p33.c
ptp_idt82p33.h
ptp_ines.c
ptp_kvm_arm.c
ptp_kvm_common.c
ptp_kvm_x86.c
ptp_mock.c
ptp_ocp.c
ptp_pch.c
ptp_private.h
ptp_qoriq.c
ptp_qoriq_debugfs.c
ptp_s390.c
ptp_sysfs.c
ptp_vclock.c
ptp_vmclock.c
ptp_vmw.c