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240325993e
[ Upstream commit 2efe41234dbd0a83fdb7cd38226c2f70039a2cd3 ]
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:
|
||
|---|---|---|
| .. | ||
| idt8a340_reg.h | ||
| Kconfig | ||
| Makefile | ||
| ptp_chardev.c | ||
| ptp_clock.c | ||
| ptp_clockmatrix.c | ||
| ptp_clockmatrix.h | ||
| ptp_dte.c | ||
| ptp_idt82p33.c | ||
| ptp_idt82p33.h | ||
| ptp_ines.c | ||
| ptp_kvm_arm.c | ||
| ptp_kvm_common.c | ||
| ptp_kvm_x86.c | ||
| ptp_ocp.c | ||
| ptp_pch.c | ||
| ptp_private.h | ||
| ptp_qoriq_debugfs.c | ||
| ptp_qoriq.c | ||
| ptp_sysfs.c | ||
| ptp_vclock.c | ||
| ptp_vmw.c | ||