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@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: 4611ce2246889 ("padata: allocate work structures for parallel jobs from a pool")
> Signed-off-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
> Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Cc: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
> Cc: linux-crypto@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> ---
> kernel/padata.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
Patch applied. Thanks.
--
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
