[PATCH net v3] mlxbf_gige: call request_irq() after NAPI initialized

From: David Thompson
Date: Mon Mar 25 2024 - 14:47:31 EST

The mlxbf_gige driver encounters a NULL pointer exception in
mlxbf_gige_open() when kdump is enabled. The sequence to reproduce
the exception is as follows:
a) enable kdump
b) trigger kdump via "echo c > /proc/sysrq-trigger"
c) kdump kernel executes
d) kdump kernel loads mlxbf_gige module
e) the mlxbf_gige module runs its open() as the
the "oob_net0" interface is brought up
f) mlxbf_gige module will experience an exception
during its open(), something like:

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
Mem abort info:
ESR = 0x0000000086000004
EC = 0x21: IABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x04: level 0 translation fault
user pgtable: 4k pages, 48-bit VAs, pgdp=00000000e29a4000
[0000000000000000] pgd=0000000000000000, p4d=0000000000000000
Internal error: Oops: 0000000086000004 [#1] SMP
CPU: 0 PID: 812 Comm: NetworkManager Tainted: G OE 5.15.0-1035-bluefield #37-Ubuntu
Hardware name: https://www.mellanox.com BlueField-3 SmartNIC Main Card/BlueField-3 SmartNIC Main Card, BIOS 4.6.0.13024 Jan 19 2024
pstate: 80400009 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : 0x0
lr : __napi_poll+0x40/0x230
sp : ffff800008003e00
x29: ffff800008003e00 x28: 0000000000000000 x27: 00000000ffffffff
x26: ffff000066027238 x25: ffff00007cedec00 x24: ffff800008003ec8
x23: 000000000000012c x22: ffff800008003eb7 x21: 0000000000000000
x20: 0000000000000001 x19: ffff000066027238 x18: 0000000000000000
x17: ffff578fcb450000 x16: ffffa870b083c7c0 x15: 0000aaab010441d0
x14: 0000000000000001 x13: 00726f7272655f65 x12: 6769675f6662786c
x11: 0000000000000000 x10: 0000000000000000 x9 : ffffa870b0842398
x8 : 0000000000000004 x7 : fe5a48b9069706ea x6 : 17fdb11fc84ae0d2
x5 : d94a82549d594f35 x4 : 0000000000000000 x3 : 0000000000400100
x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff000066027238
Call trace:
0x0
net_rx_action+0x178/0x360
__do_softirq+0x15c/0x428
__irq_exit_rcu+0xac/0xec
irq_exit+0x18/0x2c
handle_domain_irq+0x6c/0xa0
gic_handle_irq+0xec/0x1b0
call_on_irq_stack+0x20/0x2c
do_interrupt_handler+0x5c/0x70
el1_interrupt+0x30/0x50
el1h_64_irq_handler+0x18/0x2c
el1h_64_irq+0x7c/0x80
__setup_irq+0x4c0/0x950
request_threaded_irq+0xf4/0x1bc
mlxbf_gige_request_irqs+0x68/0x110 [mlxbf_gige]
mlxbf_gige_open+0x5c/0x170 [mlxbf_gige]
__dev_open+0x100/0x220
__dev_change_flags+0x16c/0x1f0
dev_change_flags+0x2c/0x70
do_setlink+0x220/0xa40
__rtnl_newlink+0x56c/0x8a0
rtnl_newlink+0x58/0x84
rtnetlink_rcv_msg+0x138/0x3c4
netlink_rcv_skb+0x64/0x130
rtnetlink_rcv+0x20/0x30
netlink_unicast+0x2ec/0x360
netlink_sendmsg+0x278/0x490
__sock_sendmsg+0x5c/0x6c
____sys_sendmsg+0x290/0x2d4
___sys_sendmsg+0x84/0xd0
__sys_sendmsg+0x70/0xd0
__arm64_sys_sendmsg+0x2c/0x40
invoke_syscall+0x78/0x100
el0_svc_common.constprop.0+0x54/0x184
do_el0_svc+0x30/0xac
el0_svc+0x48/0x160
el0t_64_sync_handler+0xa4/0x12c
el0t_64_sync+0x1a4/0x1a8
Code: bad PC value
---[ end trace 7d1c3f3bf9d81885 ]---
Kernel panic - not syncing: Oops: Fatal exception in interrupt
Kernel Offset: 0x2870a7a00000 from 0xffff800008000000
PHYS_OFFSET: 0x80000000
CPU features: 0x0,000005c1,a3332a5a
Memory Limit: none
---[ end Kernel panic - not syncing: Oops: Fatal exception in interrupt ]---

The exception happens because there is a pending RX interrupt before the
call to request_irq(RX IRQ) executes. Then, the RX IRQ handler fires
immediately after this request_irq() completes. The RX IRQ handler runs
"napi_schedule()" before NAPI is fully initialized via "netif_napi_add()"
and "napi_enable()", both which happen later in the open() logic.

The logic in mlxbf_gige_open() must fully initialize NAPI before any calls
to request_irq() execute.

Fixes: f92e1869d74e ("Add Mellanox BlueField Gigabit Ethernet driver")
Signed-off-by: David Thompson <davthompson@xxxxxxxxxx>
Reviewed-by: Asmaa Mnebhi <asmaa@xxxxxxxxxx>
---
v3
- code change to add missing phy_stop() was moved to its own commit,
which has already been merged
- re-worded commit message accordingly
v2
- re-worded commit message and subject for clarity
- updated commit message to mention that phy_stop() was added
to the error path in mlxbf_gige_open()
---
.../mellanox/mlxbf_gige/mlxbf_gige_main.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c b/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c
index cef0e2d3f1a7..77134ca92938 100644
--- a/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c
+++ b/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c
@@ -139,13 +139,10 @@ static int mlxbf_gige_open(struct net_device *netdev)
control |= MLXBF_GIGE_CONTROL_PORT_EN;
writeq(control, priv->base + MLXBF_GIGE_CONTROL);

- err = mlxbf_gige_request_irqs(priv);
- if (err)
- return err;
mlxbf_gige_cache_stats(priv);
err = mlxbf_gige_clean_port(priv);
if (err)
- goto free_irqs;
+ return err;

/* Clear driver's valid_polarity to match hardware,
* since the above call to clean_port() resets the
@@ -166,6 +163,10 @@ static int mlxbf_gige_open(struct net_device *netdev)
napi_enable(&priv->napi);
netif_start_queue(netdev);

+ err = mlxbf_gige_request_irqs(priv);
+ if (err)
+ goto napi_deinit;
+
/* Set bits in INT_EN that we care about */
int_en = MLXBF_GIGE_INT_EN_HW_ACCESS_ERROR |
MLXBF_GIGE_INT_EN_TX_CHECKSUM_INPUTS |
@@ -182,14 +183,17 @@ static int mlxbf_gige_open(struct net_device *netdev)

return 0;

+napi_deinit:
+ netif_stop_queue(netdev);
+ napi_disable(&priv->napi);
+ netif_napi_del(&priv->napi);
+ mlxbf_gige_rx_deinit(priv);
+
tx_deinit:
mlxbf_gige_tx_deinit(priv);

phy_deinit:
phy_stop(phydev);
-
-free_irqs:
- mlxbf_gige_free_irqs(priv);
return err;
}

--
2.30.1