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SubjectRe: [PATCH 4.19 091/195] padata: Remove broken queue flushing
On Fri, Feb 14, 2020 at 06:21:47PM +0800, Yang Yingliang wrote:
> Hi,
>
> On 2020/2/10 20:32, Greg Kroah-Hartman wrote:
> > From: Herbert Xu <herbert@gondor.apana.org.au>
> >
> > [ Upstream commit 07928d9bfc81640bab36f5190e8725894d93b659 ]
> >
> > The function padata_flush_queues is fundamentally broken because
> > it cannot force padata users to complete the request that is
> > underway. IOW padata has to passively wait for the completion
> > of any outstanding work.
> >
> > As it stands flushing is used in two places. Its use in padata_stop
> > is simply unnecessary because nothing depends on the queues to
> > be flushed afterwards.
> >
> > The other use in padata_replace is more substantial as we depend
> > on it to free the old pd structure. This patch instead uses the
> > pd->refcnt to dynamically free the pd structure once all requests
> > are complete.
> >
> > Fixes: 2b73b07ab8a4 ("padata: Flush the padata queues actively")
> > Cc: <stable@vger.kernel.org>
> > Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
> > Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
> > Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
> > Signed-off-by: Sasha Levin <sashal@kernel.org>
> > ---
> > kernel/padata.c | 46 ++++++++++++----------------------------------
> > 1 file changed, 12 insertions(+), 34 deletions(-)
> >
> > diff --git a/kernel/padata.c b/kernel/padata.c
> > index 6c06b3039faed..11c5f9c8779ea 100644
> > --- a/kernel/padata.c
> > +++ b/kernel/padata.c
> > @@ -35,6 +35,8 @@
> > #define MAX_OBJ_NUM 1000
> > +static void padata_free_pd(struct parallel_data *pd);
> > +
> > static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index)
> > {
> > int cpu, target_cpu;
> > @@ -334,6 +336,7 @@ static void padata_serial_worker(struct work_struct *serial_work)
> > struct padata_serial_queue *squeue;
> > struct parallel_data *pd;
> > LIST_HEAD(local_list);
> > + int cnt;
> > local_bh_disable();
> > squeue = container_of(serial_work, struct padata_serial_queue, work);
> > @@ -343,6 +346,8 @@ static void padata_serial_worker(struct work_struct *serial_work)
> > list_replace_init(&squeue->serial.list, &local_list);
> > spin_unlock(&squeue->serial.lock);
> > + cnt = 0;
> > +
> > while (!list_empty(&local_list)) {
> > struct padata_priv *padata;
> > @@ -352,9 +357,12 @@ static void padata_serial_worker(struct work_struct *serial_work)
> > list_del_init(&padata->list);
> > padata->serial(padata);
> > - atomic_dec(&pd->refcnt);
> > + cnt++;
> > }
> > local_bh_enable();
> > +
> > + if (atomic_sub_and_test(cnt, &pd->refcnt))
> > + padata_free_pd(pd);
> > }
> > /**
> > @@ -501,8 +509,7 @@ static struct parallel_data *padata_alloc_pd(struct padata_instance *pinst,
> > timer_setup(&pd->timer, padata_reorder_timer, 0);
> > atomic_set(&pd->seq_nr, -1);
> > atomic_set(&pd->reorder_objects, 0);
> > - atomic_set(&pd->refcnt, 0);
> > - pd->pinst = pinst;
> This patch remove this assignment, it's cause a null-ptr-deref when using
> pd->pinst in padata_reorder().
>
> [39135.886908] Unable to handle kernel NULL pointer dereference at virtual
> address 0000000000000010
> [39135.886909] Mem abort info:
> [39135.886910] ESR = 0x96000004
> [39135.886912] Exception class = DABT (current EL), IL = 32 bits
> [39135.886913] SET = 0, FnV = 0
> [39135.886913] EA = 0, S1PTW = 0
> [39135.886914] Data abort info:
> [39135.886915] ISV = 0, ISS = 0x00000004
> [39135.886915] CM = 0, WnR = 0
> [39135.886918] user pgtable: 4k pages, 48-bit VAs, pgdp = 00000000c66d7ef5
> [39135.886919] [0000000000000010] pgd=0000000000000000
> [39135.886922] Internal error: Oops: 96000004 [#1] SMP
> [39135.897190] Modules linked in: authenc pcrypt crypto_user cfg80211 rfkill
> ib_isert iscsi_target_mod ib_srpt target_core_mod dm_mirror dm_region_hash
> rpcrdma dm_log ib_srp scsi_transport_srp sunrpc dm_mod ib_ipoib rdma_ucm
> ib_uverbs ib_umad ib_iser rdma_cm ib_cm iw_cm aes_ce_blk crypto_simd cryptd
> aes_ce_cipher hns_roce_hw_v2 ghash_ce sha2_ce sha256_arm64 hns_roce ib_core
> sha1_ce sbsa_gwdt hi_sfc sg mtd ipmi_ssif sch_fq_codel ip_tables realtek
> hclge hinic hns3 ipmi_si hisi_sas_v3_hw hibmc_drm hnae3 hisi_sas_main
> ipmi_devintf ipmi_msghandler
> [39135.997870] Process kworker/0:2 (pid: 789, stack limit =
> 0x0000000047f55ba6)
> [39136.012707] CPU: 0 PID: 789 Comm: kworker/0:2 Kdump: loaded Not tainted
> 4.19.103+ #1
> [39136.029010] Hardware name: Huawei TaiShan 2280 V2/BC82AMDD, BIOS 1.08
> 12/14/2019
> [39136.044587] Workqueue: pencrypt padata_parallel_worker
> [39136.055396] pstate: 00c00009 (nzcv daif +PAN +UAO)
> [39136.065479] pc : padata_reorder+0x144/0x2e0
> [39136.074274] lr : padata_reorder+0x124/0x2e0
> [39136.083070] sp : ffff0000149cbc90
> [39136.090036] x29: ffff0000149cbc90 x28: 0000000000000001
> [39136.101215] x27: ffffa02fd14af080 x26: ffffa02fd5fe1600
> [39136.112392] x25: ffff5df7bf4c0ac8 x24: ffffa02fd5fe1628
> [39136.123569] x23: 0000000000000000 x22: ffff00000828a258
> [39136.134747] x21: ffffa02fd5fe1618 x20: ffff000009a79788
> [39136.145924] x19: ffff5df7bf4c0ac8 x18: 00000000bef9a3f7
> [39136.157102] x17: 0000000066bb7710 x16: 000000009a34db62
> [39136.168280] x15: 0000000000342311 x14: 0000000037c9c538
> [39136.179458] x13: 00000000deb82818 x12: 000000007abb6477
> [39136.190638] x11: 000000006e0b05e5 x10: 00000000ccde2d6a
> [39136.201817] x9 : 0000000000000000 x8 : a544a826aa446d6a
> [39136.212996] x7 : e5050b6ea3a6345c x6 : ffffa02fd74ef030
> [39136.224174] x5 : 0000000000000010 x4 : ffff5df7bf4c0ac8
> [39136.235354] x3 : ffff5df7bf4c0ad8 x2 : ffff5df7bf4c0ac8
> [39136.246532] x1 : ffff5df7bf4c0ad8 x0 : 0000000000000000
> [39136.257712] Call trace:
> [39136.262851] padata_reorder+0x144/0x2e0
> [39136.270922] padata_do_serial+0xc8/0x128
> [39136.279177] pcrypt_aead_enc+0x60/0x70 [pcrypt]
> [39136.288708] padata_parallel_worker+0xd8/0x138
> [39136.298056] process_one_work+0x1bc/0x4b8
> [39136.306489] worker_thread+0x164/0x580
> [39136.314374] kthread+0x134/0x138
> [39136.321163] ret_from_fork+0x10/0x18
> [39136.328681] Code: f900033b 52800000 91004261 089ffc20 (f9400ae1)
> [39136.341508] ---[ end trace fc1b4f00385f0fee ]---
> [39136.351221] Kernel panic - not syncing: Fatal exception in interrupt
> [39136.364591] SMP: stopping secondary CPUs
> [39136.372863] Kernel Offset: disabled
> [39138.438722] CPU features: 0x12,a2200a38
> [39138.446797] Memory Limit: none
> [39138.463025] Starting crashdump kernel...
> [39138.471295] Bye!

So this causes a problem in the 4.19-rc tree but not in Linus's tree?
Or am I confused? Should it be dropped from stable or is there some
other fix-of-a-fix that I need to apply here?

thanks,

greg k-h

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