[PATCH 5.3 151/166] net: dsa: sja1105: Fix sleeping while atomic in .port_hwtstamp_set

Greg Kroah-Hartman
2019-10-06T17:51:32Z

From: Vladimir Oltean <olteanv@gmail.com>

[ Upstream commit 3e8db7e56082156a37b71d7334860c10fcea8025 ]

Currently this stack trace can be seen with CONFIG_DEBUG_ATOMIC_SLEEP=y:

[ 41.568348] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:909
[ 41.576757] in_atomic(): 1, irqs_disabled(): 0, pid: 208, name: ptp4l
[ 41.583212] INFO: lockdep is turned off.
[ 41.587123] CPU: 1 PID: 208 Comm: ptp4l Not tainted 5.3.0-rc6-01445-ge950f2d4bc7f-dirty #1827
[ 41.599873] [<c0313d7c>] (unwind_backtrace) from [<c030e13c>] (show_stack+0x10/0x14)
[ 41.607584] [<c030e13c>] (show_stack) from [<c1212d50>] (dump_stack+0xd4/0x100)
[ 41.614863] [<c1212d50>] (dump_stack) from [<c037dfc8>] (___might_sleep+0x1c8/0x2b4)
[ 41.622574] [<c037dfc8>] (___might_sleep) from [<c122ea90>] (__mutex_lock+0x48/0xab8)
[ 41.630368] [<c122ea90>] (__mutex_lock) from [<c122f51c>] (mutex_lock_nested+0x1c/0x24)
[ 41.638340] [<c122f51c>] (mutex_lock_nested) from [<c0c6fe08>] (sja1105_static_config_reload+0x30/0x27c)
[ 41.647779] [<c0c6fe08>] (sja1105_static_config_reload) from [<c0c7015c>] (sja1105_hwtstamp_set+0x108/0x1cc)
[ 41.657562] [<c0c7015c>] (sja1105_hwtstamp_set) from [<c0feb650>] (dev_ifsioc+0x18c/0x330)
[ 41.665788] [<c0feb650>] (dev_ifsioc) from [<c0febbd8>] (dev_ioctl+0x320/0x6e8)
[ 41.673064] [<c0febbd8>] (dev_ioctl) from [<c0f8b1f4>] (sock_ioctl+0x334/0x5e8)
[ 41.680340] [<c0f8b1f4>] (sock_ioctl) from [<c05404a8>] (do_vfs_ioctl+0xb0/0xa10)
[ 41.687789] [<c05404a8>] (do_vfs_ioctl) from [<c0540e3c>] (ksys_ioctl+0x34/0x58)
[ 41.695151] [<c0540e3c>] (ksys_ioctl) from [<c0301000>] (ret_fast_syscall+0x0/0x28)
[ 41.702768] Exception stack(0xe8495fa8 to 0xe8495ff0)
[ 41.707796] 5fa0: beff4a8c 00000001 00000011 000089b0 beff4a8c beff4a80
[ 41.715933] 5fc0: beff4a8c 00000001 0000000c 00000036 b6fa98c8 004e19c1 00000001 00000000
[ 41.724069] 5fe0: 004dcedc beff4a6c 004c0738 b6e7af4c
[ 41.729860] BUG: scheduling while atomic: ptp4l/208/0x00000002
[ 41.735682] INFO: lockdep is turned off.

Enabling RX timestamping will logically disturb the fastpath (processing
of meta frames). Replace bool hwts_rx_en with a bit that is checked
atomically from the fastpath and temporarily unset from the sleepable
context during a change of the RX timestamping process (a destructive
operation anyways, requires switch reset).
If found unset, the fastpath (net/dsa/tag_sja1105.c) will just drop any
received meta frame and not take the meta_lock at all.

Fixes: a602afd200f5 ("net: dsa: sja1105: Expose PTP timestamping ioctls to userspace")
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/dsa/sja1105/sja1105_main.c | 19 +++++++++++--------
include/linux/dsa/sja1105.h | 4 +++-
net/dsa/tag_sja1105.c | 12 +++++++++++-
3 files changed, 25 insertions(+), 10 deletions(-)

--- a/drivers/net/dsa/sja1105/sja1105_main.c
+++ b/drivers/net/dsa/sja1105/sja1105_main.c
@@ -1875,7 +1875,9 @@ static int sja1105_set_ageing_time(struc
return sja1105_static_config_reload(priv);
}

-/* Caller must hold priv->tagger_data.meta_lock */
+/* Must be called only with priv->tagger_data.state bit
+ * SJA1105_HWTS_RX_EN cleared
+ */
static int sja1105_change_rxtstamping(struct sja1105_private *priv,
bool on)
{
@@ -1932,16 +1934,17 @@ static int sja1105_hwtstamp_set(struct d
break;
}

- if (rx_on != priv->tagger_data.hwts_rx_en) {
- spin_lock(&priv->tagger_data.meta_lock);
+ if (rx_on != test_bit(SJA1105_HWTS_RX_EN, &priv->tagger_data.state)) {
+ clear_bit(SJA1105_HWTS_RX_EN, &priv->tagger_data.state);
+
rc = sja1105_change_rxtstamping(priv, rx_on);
- spin_unlock(&priv->tagger_data.meta_lock);
if (rc < 0) {
dev_err(ds->dev,
"Failed to change RX timestamping: %d\n", rc);
- return -EFAULT;
+ return rc;
}
- priv->tagger_data.hwts_rx_en = rx_on;
+ if (rx_on)
+ set_bit(SJA1105_HWTS_RX_EN, &priv->tagger_data.state);
}

if (copy_to_user(ifr->ifr_data, &config, sizeof(config)))
@@ -1960,7 +1963,7 @@ static int sja1105_hwtstamp_get(struct d
config.tx_type = HWTSTAMP_TX_ON;
else
config.tx_type = HWTSTAMP_TX_OFF;
- if (priv->tagger_data.hwts_rx_en)
+ if (test_bit(SJA1105_HWTS_RX_EN, &priv->tagger_data.state))
config.rx_filter = HWTSTAMP_FILTER_PTP_V2_L2_EVENT;
else
config.rx_filter = HWTSTAMP_FILTER_NONE;
@@ -2009,7 +2012,7 @@ static bool sja1105_port_rxtstamp(struct
struct sja1105_private *priv = ds->priv;
struct sja1105_tagger_data *data = &priv->tagger_data;

- if (!data->hwts_rx_en)
+ if (!test_bit(SJA1105_HWTS_RX_EN, &data->state))
return false;

/* We need to read the full PTP clock to reconstruct the Rx
--- a/include/linux/dsa/sja1105.h
+++ b/include/linux/dsa/sja1105.h
@@ -31,6 +31,8 @@
#define SJA1105_META_SMAC 0x222222222222ull
#define SJA1105_META_DMAC 0x0180C200000Eull

+#define SJA1105_HWTS_RX_EN 0
+
/* Global tagger data: each struct sja1105_port has a reference to
* the structure defined in struct sja1105_private.
*/
@@ -42,7 +44,7 @@ struct sja1105_tagger_data {
* from taggers running on multiple ports on SMP systems
*/
spinlock_t meta_lock;
- bool hwts_rx_en;
+ unsigned long state;
};

struct sja1105_skb_cb {
--- a/net/dsa/tag_sja1105.c
+++ b/net/dsa/tag_sja1105.c
@@ -155,7 +155,11 @@ static struct sk_buff
/* Step 1: A timestampable frame was received.
* Buffer it until we get its meta frame.
*/
- if (is_link_local && sp->data->hwts_rx_en) {
+ if (is_link_local) {
+ if (!test_bit(SJA1105_HWTS_RX_EN, &sp->data->state))
+ /* Do normal processing. */
+ return skb;
+
spin_lock(&sp->data->meta_lock);
/* Was this a link-local frame instead of the meta
* that we were expecting?
@@ -186,6 +190,12 @@ static struct sk_buff
} else if (is_meta) {
struct sk_buff *stampable_skb;

+ /* Drop the meta frame if we're not in the right state
+ * to process it.
+ */
+ if (!test_bit(SJA1105_HWTS_RX_EN, &sp->data->state))
+ return NULL;
+
spin_lock(&sp->data->meta_lock);

stampable_skb = sp->data->stampable_skb;