| Message ID | 20200902170756.332491-1-daniel.m.jordan@oracle.com (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | Herbert Xu |
| Headers | show |
| Series | padata: fix possible padata_works_lock deadlock | expand |
On Wed, Sep 02, 2020 at 01:07:56PM -0400, Daniel Jordan wrote: > 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); > <Interrupt> > 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 <daniel.m.jordan@oracle.com> > Cc: Herbert Xu <herbert@gondor.apana.org.au> > Cc: Steffen Klassert <steffen.klassert@secunet.com> > Cc: linux-crypto@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > --- > kernel/padata.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) Patch applied. Thanks.
diff --git a/kernel/padata.c b/kernel/padata.c index 16cb894dc272..d4d3ba6e1728 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);
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); <Interrupt> 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 <daniel.m.jordan@oracle.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Steffen Klassert <steffen.klassert@secunet.com> Cc: linux-crypto@vger.kernel.org Cc: linux-kernel@vger.kernel.org --- kernel/padata.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) base-commit: 9c7d619be5a002ea29c172df5e3c1227c22cbb41