diff options
| author | Waiman Long <longman@redhat.com> | 2022-02-08 11:39:12 -0500 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2022-02-11 09:28:32 +0100 |
| commit | ddc204b517e60ae64db34f9832dc41dafa77c751 (patch) | |
| tree | 4ebc10047041be7ca802e7678a0893d4adc72497 /kernel/fork.c | |
| parent | dfd42facf1e4ada021b939b4e19c935dcdd55566 (diff) | |
copy_process(): Move fd_install() out of sighand->siglock critical section
I was made aware of the following lockdep splat:
[ 2516.308763] =====================================================
[ 2516.309085] WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
[ 2516.309433] 5.14.0-51.el9.aarch64+debug #1 Not tainted
[ 2516.309703] -----------------------------------------------------
[ 2516.310149] stress-ng/153663 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
[ 2516.310512] ffff0000e422b198 (&newf->file_lock){+.+.}-{2:2}, at: fd_install+0x368/0x4f0
[ 2516.310944]
and this task is already holding:
[ 2516.311248] ffff0000c08140d8 (&sighand->siglock){-.-.}-{2:2}, at: copy_process+0x1e2c/0x3e80
[ 2516.311804] which would create a new lock dependency:
[ 2516.312066] (&sighand->siglock){-.-.}-{2:2} -> (&newf->file_lock){+.+.}-{2:2}
[ 2516.312446]
but this new dependency connects a HARDIRQ-irq-safe lock:
[ 2516.312983] (&sighand->siglock){-.-.}-{2:2}
:
[ 2516.330700] Possible interrupt unsafe locking scenario:
[ 2516.331075] CPU0 CPU1
[ 2516.331328] ---- ----
[ 2516.331580] lock(&newf->file_lock);
[ 2516.331790] local_irq_disable();
[ 2516.332231] lock(&sighand->siglock);
[ 2516.332579] lock(&newf->file_lock);
[ 2516.332922] <Interrupt>
[ 2516.333069] lock(&sighand->siglock);
[ 2516.333291]
*** DEADLOCK ***
[ 2516.389845]
stack backtrace:
[ 2516.390101] CPU: 3 PID: 153663 Comm: stress-ng Kdump: loaded Not tainted 5.14.0-51.el9.aarch64+debug #1
[ 2516.390756] Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015
[ 2516.391155] Call trace:
[ 2516.391302] dump_backtrace+0x0/0x3e0
[ 2516.391518] show_stack+0x24/0x30
[ 2516.391717] dump_stack_lvl+0x9c/0xd8
[ 2516.391938] dump_stack+0x1c/0x38
[ 2516.392247] print_bad_irq_dependency+0x620/0x710
[ 2516.392525] check_irq_usage+0x4fc/0x86c
[ 2516.392756] check_prev_add+0x180/0x1d90
[ 2516.392988] validate_chain+0x8e0/0xee0
[ 2516.393215] __lock_acquire+0x97c/0x1e40
[ 2516.393449] lock_acquire.part.0+0x240/0x570
[ 2516.393814] lock_acquire+0x90/0xb4
[ 2516.394021] _raw_spin_lock+0xe8/0x154
[ 2516.394244] fd_install+0x368/0x4f0
[ 2516.394451] copy_process+0x1f5c/0x3e80
[ 2516.394678] kernel_clone+0x134/0x660
[ 2516.394895] __do_sys_clone3+0x130/0x1f4
[ 2516.395128] __arm64_sys_clone3+0x5c/0x7c
[ 2516.395478] invoke_syscall.constprop.0+0x78/0x1f0
[ 2516.395762] el0_svc_common.constprop.0+0x22c/0x2c4
[ 2516.396050] do_el0_svc+0xb0/0x10c
[ 2516.396252] el0_svc+0x24/0x34
[ 2516.396436] el0t_64_sync_handler+0xa4/0x12c
[ 2516.396688] el0t_64_sync+0x198/0x19c
[ 2517.491197] NET: Registered PF_ATMPVC protocol family
[ 2517.491524] NET: Registered PF_ATMSVC protocol family
[ 2591.991877] sched: RT throttling activated
One way to solve this problem is to move the fd_install() call out of
the sighand->siglock critical section.
Before commit 6fd2fe494b17 ("copy_process(): don't use ksys_close()
on cleanups"), the pidfd installation was done without holding both
the task_list lock and the sighand->siglock. Obviously, holding these
two locks are not really needed to protect the fd_install() call.
So move the fd_install() call down to after the releases of both locks.
Link: https://lore.kernel.org/r/20220208163912.1084752-1-longman@redhat.com
Fixes: 6fd2fe494b17 ("copy_process(): don't use ksys_close() on cleanups")
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'kernel/fork.c')
| -rw-r--r-- | kernel/fork.c | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index d75a528f7b21..007af7fb47c7 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2323,10 +2323,6 @@ static __latent_entropy struct task_struct *copy_process( goto bad_fork_cancel_cgroup; } - /* past the last point of failure */ - if (pidfile) - fd_install(pidfd, pidfile); - init_task_pid_links(p); if (likely(p->pid)) { ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); @@ -2375,6 +2371,9 @@ static __latent_entropy struct task_struct *copy_process( syscall_tracepoint_update(p); write_unlock_irq(&tasklist_lock); + if (pidfile) + fd_install(pidfd, pidfile); + proc_fork_connector(p); sched_post_fork(p, args); cgroup_post_fork(p, args); |