| Message ID | 20230707104359.3324039-2-schnelle@linux.ibm.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net,v2,1/3] s390/ism: Fix locking for forwarding of IRQs and events to clients | expand |
On Fri, 2023-07-07 at 12:43 +0200, Niklas Schnelle wrote: > The clients array references all registered clients and is protected by > the clients_lock. Besides its use as general list of clients the clients > array is accessed in ism_handle_irq() to forward ISM device events to > clients. > > While the clients_lock is taken in the IRQ handler when calling > handle_event() it is however incorrectly not held during the > client->handle_irq() call and for the preceding clients[] access leaving > it unprotected against concurrent client (un-)registration. > > Furthermore the accesses to ism->sba_client_arr[] in ism_register_dmb() > and ism_unregister_dmb() are not protected by any lock. This is > especially problematic as the client ID from the ism->sba_client_arr[] > is not checked against NO_CLIENT and neither is the client pointer > checked. > > Instead of expanding the use of the clients_lock further add a separate > array in struct ism_dev which references clients subscribed to the > device's events and IRQs. This array is protected by ism->lock which is > already taken in ism_handle_irq() and can be taken outside the IRQ > handler when adding/removing subscribers or the accessing > ism->sba_client_arr[]. This also means that the clients_lock is no > longer taken in IRQ context. > > Fixes: 89e7d2ba61b7 ("net/ism: Add new API for client registration") > Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com> > --- Sorry for the mess. My get_maintainers.pl to-cmd setup in git send- email stumbled over the cover letter and so the cover letter was not sent to the right people/lists messing up the "in-reply-to" references. So I had to resend it. Thanks Niklas
On Fri, Jul 07, 2023 at 12:43:57PM +0200, Niklas Schnelle wrote: > The clients array references all registered clients and is protected by > the clients_lock. Besides its use as general list of clients the clients > array is accessed in ism_handle_irq() to forward ISM device events to > clients. > > While the clients_lock is taken in the IRQ handler when calling > handle_event() it is however incorrectly not held during the > client->handle_irq() call and for the preceding clients[] access leaving > it unprotected against concurrent client (un-)registration. > > Furthermore the accesses to ism->sba_client_arr[] in ism_register_dmb() > and ism_unregister_dmb() are not protected by any lock. This is > especially problematic as the client ID from the ism->sba_client_arr[] > is not checked against NO_CLIENT and neither is the client pointer > checked. > > Instead of expanding the use of the clients_lock further add a separate > array in struct ism_dev which references clients subscribed to the > device's events and IRQs. This array is protected by ism->lock which is > already taken in ism_handle_irq() and can be taken outside the IRQ > handler when adding/removing subscribers or the accessing > ism->sba_client_arr[]. This also means that the clients_lock is no > longer taken in IRQ context. > > Fixes: 89e7d2ba61b7 ("net/ism: Add new API for client registration") > Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com> ... > @@ -71,6 +80,7 @@ int ism_register_client(struct ism_client *client) > list_for_each_entry(ism, &ism_dev_list.list, list) { > ism->priv[i] = NULL; > client->add(ism); > + ism_setup_forwarding(client, ism); > } > } > mutex_unlock(&ism_dev_list.mutex); ... > @@ -92,6 +102,9 @@ int ism_unregister_client(struct ism_client *client) > max_client--; > spin_unlock_irqrestore(&clients_lock, flags); > list_for_each_entry(ism, &ism_dev_list.list, list) { > + spin_lock_irqsave(&ism->lock, flags); Hi Niklas, The lock is taken here. > + /* Stop forwarding IRQs and events */ > + ism->subs[client->id] = NULL; > for (int i = 0; i < ISM_NR_DMBS; ++i) { > if (ism->sba_client_arr[i] == client->id) { > pr_err("%s: attempt to unregister client '%s'" > @@ -101,6 +114,7 @@ int ism_unregister_client(struct ism_client *client) > goto out; But it does not appear to be released (by the call to spin_unlock_irqrestore() below) if goto out is called here. > } > } > + spin_unlock_irqrestore(&ism->lock, flags); > } > out: > mutex_unlock(&ism_dev_list.mutex);
On 08.07.23 15:36, Simon Horman wrote: > On Fri, Jul 07, 2023 at 12:43:57PM +0200, Niklas Schnelle wrote: [...] >> @@ -92,6 +102,9 @@ int ism_unregister_client(struct ism_client *client) >> max_client--; >> spin_unlock_irqrestore(&clients_lock, flags); >> list_for_each_entry(ism, &ism_dev_list.list, list) { >> + spin_lock_irqsave(&ism->lock, flags); > > Hi Niklas, > > The lock is taken here. > >> + /* Stop forwarding IRQs and events */ >> + ism->subs[client->id] = NULL; >> for (int i = 0; i < ISM_NR_DMBS; ++i) { >> if (ism->sba_client_arr[i] == client->id) { >> pr_err("%s: attempt to unregister client '%s'" >> @@ -101,6 +114,7 @@ int ism_unregister_client(struct ism_client *client) >> goto out; > > But it does not appear to be released > (by the call to spin_unlock_irqrestore() below) > if goto out is called here. > >> } >> } >> + spin_unlock_irqrestore(&ism->lock, flags); >> } >> out: >> mutex_unlock(&ism_dev_list.mutex); > Great catch, Simon. @Niklas, the missing unlock accidentially got moved to "[PATCH net v2 3/3] s390/ism: Do not unregister clients with registered DMBs"
On Sat, 2023-07-08 at 14:36 +0100, Simon Horman wrote: > On Fri, Jul 07, 2023 at 12:43:57PM +0200, Niklas Schnelle wrote: > > The clients array references all registered clients and is protected by > > the clients_lock. Besides its use as general list of clients the clients > > array is accessed in ism_handle_irq() to forward ISM device events to > > clients. > > > > While the clients_lock is taken in the IRQ handler when calling > > handle_event() it is however incorrectly not held during the > > client->handle_irq() call and for the preceding clients[] access leaving > > it unprotected against concurrent client (un-)registration. > > > > Furthermore the accesses to ism->sba_client_arr[] in ism_register_dmb() > > and ism_unregister_dmb() are not protected by any lock. This is > > especially problematic as the client ID from the ism->sba_client_arr[] > > is not checked against NO_CLIENT and neither is the client pointer > > checked. > > > > Instead of expanding the use of the clients_lock further add a separate > > array in struct ism_dev which references clients subscribed to the > > device's events and IRQs. This array is protected by ism->lock which is > > already taken in ism_handle_irq() and can be taken outside the IRQ > > handler when adding/removing subscribers or the accessing > > ism->sba_client_arr[]. This also means that the clients_lock is no > > longer taken in IRQ context. > > > > Fixes: 89e7d2ba61b7 ("net/ism: Add new API for client registration") > > Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com> > > ... > > > @@ -71,6 +80,7 @@ int ism_register_client(struct ism_client *client) > > list_for_each_entry(ism, &ism_dev_list.list, list) { > > ism->priv[i] = NULL; > > client->add(ism); > > + ism_setup_forwarding(client, ism); > > } > > } > > mutex_unlock(&ism_dev_list.mutex); > > ... > > > @@ -92,6 +102,9 @@ int ism_unregister_client(struct ism_client *client) > > max_client--; > > spin_unlock_irqrestore(&clients_lock, flags); > > list_for_each_entry(ism, &ism_dev_list.list, list) { > > + spin_lock_irqsave(&ism->lock, flags); > > Hi Niklas, > > The lock is taken here. > > > + /* Stop forwarding IRQs and events */ > > + ism->subs[client->id] = NULL; > > for (int i = 0; i < ISM_NR_DMBS; ++i) { > > if (ism->sba_client_arr[i] == client->id) { > > pr_err("%s: attempt to unregister client '%s'" > > @@ -101,6 +114,7 @@ int ism_unregister_client(struct ism_client *client) > > goto out; > > But it does not appear to be released > (by the call to spin_unlock_irqrestore() below) > if goto out is called here. Good catch. Yes I screwed this up while splitting the patch up. The spin_unlock_irqrestore() is there after patch 3 but should have been added in patch 1. As far as I can see all 3 patches have already been applied, otherwise I'd send a v3. Thankfully even in the in between state this error case can really onlt happen due to driver bugs so maybe it's okay? > > > } > > } > > + spin_unlock_irqrestore(&ism->lock, flags); > > } > > out: > > mutex_unlock(&ism_dev_list.mutex);
On Mon, Jul 10, 2023 at 09:28:20AM +0200, Niklas Schnelle wrote: > On Sat, 2023-07-08 at 14:36 +0100, Simon Horman wrote: > > On Fri, Jul 07, 2023 at 12:43:57PM +0200, Niklas Schnelle wrote: > > > The clients array references all registered clients and is protected by > > > the clients_lock. Besides its use as general list of clients the clients > > > array is accessed in ism_handle_irq() to forward ISM device events to > > > clients. > > > > > > While the clients_lock is taken in the IRQ handler when calling > > > handle_event() it is however incorrectly not held during the > > > client->handle_irq() call and for the preceding clients[] access leaving > > > it unprotected against concurrent client (un-)registration. > > > > > > Furthermore the accesses to ism->sba_client_arr[] in ism_register_dmb() > > > and ism_unregister_dmb() are not protected by any lock. This is > > > especially problematic as the client ID from the ism->sba_client_arr[] > > > is not checked against NO_CLIENT and neither is the client pointer > > > checked. > > > > > > Instead of expanding the use of the clients_lock further add a separate > > > array in struct ism_dev which references clients subscribed to the > > > device's events and IRQs. This array is protected by ism->lock which is > > > already taken in ism_handle_irq() and can be taken outside the IRQ > > > handler when adding/removing subscribers or the accessing > > > ism->sba_client_arr[]. This also means that the clients_lock is no > > > longer taken in IRQ context. > > > > > > Fixes: 89e7d2ba61b7 ("net/ism: Add new API for client registration") > > > Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com> > > > > ... > > > > > @@ -71,6 +80,7 @@ int ism_register_client(struct ism_client *client) > > > list_for_each_entry(ism, &ism_dev_list.list, list) { > > > ism->priv[i] = NULL; > > > client->add(ism); > > > + ism_setup_forwarding(client, ism); > > > } > > > } > > > mutex_unlock(&ism_dev_list.mutex); > > > > ... > > > > > @@ -92,6 +102,9 @@ int ism_unregister_client(struct ism_client *client) > > > max_client--; > > > spin_unlock_irqrestore(&clients_lock, flags); > > > list_for_each_entry(ism, &ism_dev_list.list, list) { > > > + spin_lock_irqsave(&ism->lock, flags); > > > > Hi Niklas, > > > > The lock is taken here. > > > > > + /* Stop forwarding IRQs and events */ > > > + ism->subs[client->id] = NULL; > > > for (int i = 0; i < ISM_NR_DMBS; ++i) { > > > if (ism->sba_client_arr[i] == client->id) { > > > pr_err("%s: attempt to unregister client '%s'" > > > @@ -101,6 +114,7 @@ int ism_unregister_client(struct ism_client *client) > > > goto out; > > > > But it does not appear to be released > > (by the call to spin_unlock_irqrestore() below) > > if goto out is called here. > > Good catch. Yes I screwed this up while splitting the patch up. The > spin_unlock_irqrestore() is there after patch 3 but should have been > added in patch 1. As far as I can see all 3 patches have already been > applied, otherwise I'd send a v3. Thankfully even in the in between > state this error case can really onlt happen due to driver bugs so > maybe it's okay? Hi Niklas, I also saw the patches have been accepted after I sent my previous email. So, given that the problem is resolved by another patch in the series, I think the situation is as good as it is going to get.
diff --git a/drivers/s390/net/ism_drv.c b/drivers/s390/net/ism_drv.c index 9b5fccdbc7d6..b664e4a08645 100644 --- a/drivers/s390/net/ism_drv.c +++ b/drivers/s390/net/ism_drv.c @@ -47,6 +47,15 @@ static struct ism_dev_list ism_dev_list = { .mutex = __MUTEX_INITIALIZER(ism_dev_list.mutex), }; +static void ism_setup_forwarding(struct ism_client *client, struct ism_dev *ism) +{ + unsigned long flags; + + spin_lock_irqsave(&ism->lock, flags); + ism->subs[client->id] = client; + spin_unlock_irqrestore(&ism->lock, flags); +} + int ism_register_client(struct ism_client *client) { struct ism_dev *ism; @@ -71,6 +80,7 @@ int ism_register_client(struct ism_client *client) list_for_each_entry(ism, &ism_dev_list.list, list) { ism->priv[i] = NULL; client->add(ism); + ism_setup_forwarding(client, ism); } } mutex_unlock(&ism_dev_list.mutex); @@ -92,6 +102,9 @@ int ism_unregister_client(struct ism_client *client) max_client--; spin_unlock_irqrestore(&clients_lock, flags); list_for_each_entry(ism, &ism_dev_list.list, list) { + spin_lock_irqsave(&ism->lock, flags); + /* Stop forwarding IRQs and events */ + ism->subs[client->id] = NULL; for (int i = 0; i < ISM_NR_DMBS; ++i) { if (ism->sba_client_arr[i] == client->id) { pr_err("%s: attempt to unregister client '%s'" @@ -101,6 +114,7 @@ int ism_unregister_client(struct ism_client *client) goto out; } } + spin_unlock_irqrestore(&ism->lock, flags); } out: mutex_unlock(&ism_dev_list.mutex); @@ -328,6 +342,7 @@ int ism_register_dmb(struct ism_dev *ism, struct ism_dmb *dmb, struct ism_client *client) { union ism_reg_dmb cmd; + unsigned long flags; int ret; ret = ism_alloc_dmb(ism, dmb); @@ -351,7 +366,9 @@ int ism_register_dmb(struct ism_dev *ism, struct ism_dmb *dmb, goto out; } dmb->dmb_tok = cmd.response.dmb_tok; + spin_lock_irqsave(&ism->lock, flags); ism->sba_client_arr[dmb->sba_idx - ISM_DMB_BIT_OFFSET] = client->id; + spin_unlock_irqrestore(&ism->lock, flags); out: return ret; } @@ -360,6 +377,7 @@ EXPORT_SYMBOL_GPL(ism_register_dmb); int ism_unregister_dmb(struct ism_dev *ism, struct ism_dmb *dmb) { union ism_unreg_dmb cmd; + unsigned long flags; int ret; memset(&cmd, 0, sizeof(cmd)); @@ -368,7 +386,9 @@ int ism_unregister_dmb(struct ism_dev *ism, struct ism_dmb *dmb) cmd.request.dmb_tok = dmb->dmb_tok; + spin_lock_irqsave(&ism->lock, flags); ism->sba_client_arr[dmb->sba_idx - ISM_DMB_BIT_OFFSET] = NO_CLIENT; + spin_unlock_irqrestore(&ism->lock, flags); ret = ism_cmd(ism, &cmd); if (ret && ret != ISM_ERROR) @@ -491,6 +511,7 @@ static u16 ism_get_chid(struct ism_dev *ism) static void ism_handle_event(struct ism_dev *ism) { struct ism_event *entry; + struct ism_client *clt; int i; while ((ism->ieq_idx + 1) != READ_ONCE(ism->ieq->header.idx)) { @@ -499,21 +520,21 @@ static void ism_handle_event(struct ism_dev *ism) entry = &ism->ieq->entry[ism->ieq_idx]; debug_event(ism_debug_info, 2, entry, sizeof(*entry)); - spin_lock(&clients_lock); - for (i = 0; i < max_client; ++i) - if (clients[i]) - clients[i]->handle_event(ism, entry); - spin_unlock(&clients_lock); + for (i = 0; i < max_client; ++i) { + clt = ism->subs[i]; + if (clt) + clt->handle_event(ism, entry); + } } } static irqreturn_t ism_handle_irq(int irq, void *data) { struct ism_dev *ism = data; - struct ism_client *clt; unsigned long bit, end; unsigned long *bv; u16 dmbemask; + u8 client_id; bv = (void *) &ism->sba->dmb_bits[ISM_DMB_WORD_OFFSET]; end = sizeof(ism->sba->dmb_bits) * BITS_PER_BYTE - ISM_DMB_BIT_OFFSET; @@ -530,8 +551,10 @@ static irqreturn_t ism_handle_irq(int irq, void *data) dmbemask = ism->sba->dmbe_mask[bit + ISM_DMB_BIT_OFFSET]; ism->sba->dmbe_mask[bit + ISM_DMB_BIT_OFFSET] = 0; barrier(); - clt = clients[ism->sba_client_arr[bit]]; - clt->handle_irq(ism, bit + ISM_DMB_BIT_OFFSET, dmbemask); + client_id = ism->sba_client_arr[bit]; + if (unlikely(client_id == NO_CLIENT || !ism->subs[client_id])) + continue; + ism->subs[client_id]->handle_irq(ism, bit + ISM_DMB_BIT_OFFSET, dmbemask); } if (ism->sba->e) { @@ -554,6 +577,7 @@ static void ism_dev_add_work_func(struct work_struct *work) add_work); client->add(client->tgt_ism); + ism_setup_forwarding(client, client->tgt_ism); atomic_dec(&client->tgt_ism->add_dev_cnt); wake_up(&client->tgt_ism->waitq); } @@ -691,7 +715,11 @@ static void ism_dev_remove_work_func(struct work_struct *work) { struct ism_client *client = container_of(work, struct ism_client, remove_work); + unsigned long flags; + spin_lock_irqsave(&client->tgt_ism->lock, flags); + client->tgt_ism->subs[client->id] = NULL; + spin_unlock_irqrestore(&client->tgt_ism->lock, flags); client->remove(client->tgt_ism); atomic_dec(&client->tgt_ism->free_clients_cnt); wake_up(&client->tgt_ism->waitq); diff --git a/include/linux/ism.h b/include/linux/ism.h index ea2bcdae7401..5160d47e5ea9 100644 --- a/include/linux/ism.h +++ b/include/linux/ism.h @@ -44,6 +44,7 @@ struct ism_dev { u64 local_gid; int ieq_idx; + struct ism_client *subs[MAX_CLIENTS]; atomic_t free_clients_cnt; atomic_t add_dev_cnt; wait_queue_head_t waitq;
The clients array references all registered clients and is protected by the clients_lock. Besides its use as general list of clients the clients array is accessed in ism_handle_irq() to forward ISM device events to clients. While the clients_lock is taken in the IRQ handler when calling handle_event() it is however incorrectly not held during the client->handle_irq() call and for the preceding clients[] access leaving it unprotected against concurrent client (un-)registration. Furthermore the accesses to ism->sba_client_arr[] in ism_register_dmb() and ism_unregister_dmb() are not protected by any lock. This is especially problematic as the client ID from the ism->sba_client_arr[] is not checked against NO_CLIENT and neither is the client pointer checked. Instead of expanding the use of the clients_lock further add a separate array in struct ism_dev which references clients subscribed to the device's events and IRQs. This array is protected by ism->lock which is already taken in ism_handle_irq() and can be taken outside the IRQ handler when adding/removing subscribers or the accessing ism->sba_client_arr[]. This also means that the clients_lock is no longer taken in IRQ context. Fixes: 89e7d2ba61b7 ("net/ism: Add new API for client registration") Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com> --- drivers/s390/net/ism_drv.c | 44 +++++++++++++++++++++++++++++++------- include/linux/ism.h | 1 + 2 files changed, 37 insertions(+), 8 deletions(-)