From: Daniel Jordan Date: Wed, 2 Sep 2020 17:07:56 +0000 (-0400) Subject: padata: fix possible padata_works_lock deadlock X-Git-Tag: v5.8.10~141 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=412bbf8b9a22c8635773a12f08c897b7f91ab6fc;p=thirdparty%2Fkernel%2Fstable.git padata: fix possible padata_works_lock deadlock [ Upstream commit 1b0df11fde0f14a269a181b3b7f5122415bc5ed7 ] syzbot reports, WARNING: inconsistent lock state 5.9.0-rc2-syzkaller #0 Not tainted -------------------------------- inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage. syz-executor.0/26715 takes: (padata_works_lock){+.?.}-{2:2}, at: padata_do_parallel kernel/padata.c:220 {IN-SOFTIRQ-W} state was registered at: spin_lock include/linux/spinlock.h:354 [inline] padata_do_parallel kernel/padata.c:220 ... __do_softirq kernel/softirq.c:298 ... sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1091 asm_sysvec_apic_timer_interrupt arch/x86/include/asm/idtentry.h:581 Possible unsafe locking scenario: CPU0 ---- lock(padata_works_lock); lock(padata_works_lock); padata_do_parallel() takes padata_works_lock with softirqs enabled, so a deadlock is possible if, on the same CPU, the lock is acquired in process context and then softirq handling done in an interrupt leads to the same path. Fix by leaving softirqs disabled while do_parallel holds padata_works_lock. Reported-by: syzbot+f4b9f49e38e25eb4ef52@syzkaller.appspotmail.com Fixes: 4611ce2246889 ("padata: allocate work structures for parallel jobs from a pool") Signed-off-by: Daniel Jordan Cc: Herbert Xu Cc: Steffen Klassert Cc: linux-crypto@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Herbert Xu Signed-off-by: Sasha Levin --- diff --git a/kernel/padata.c b/kernel/padata.c index 4373f7adaa40a..3bc90fec0904c 100644 --- a/kernel/padata.c +++ b/kernel/padata.c @@ -215,12 +215,13 @@ int padata_do_parallel(struct padata_shell *ps, padata->pd = pd; padata->cb_cpu = *cb_cpu; - rcu_read_unlock_bh(); - spin_lock(&padata_works_lock); padata->seq_nr = ++pd->seq_nr; pw = padata_work_alloc(); spin_unlock(&padata_works_lock); + + rcu_read_unlock_bh(); + if (pw) { padata_work_init(pw, padata_parallel_worker, padata, 0); queue_work(pinst->parallel_wq, &pw->pw_work);