Re: [PATCH net-next,v4] bonding: return -ENOMEM instead of BUG in alb_upper_dev_walk

On 2023/11/21 19:41, Paolo Abeni wrote:

On Sat, 2023-11-18 at 16:16 +0800, Zhengchao Shao wrote:

quoted

If failed to allocate "tags" or could not find the final upper device from
start_dev's upper list in bond_verify_device_path(), only the loopback
detection of the current upper device should be affected, and the system is
no need to be panic.
So return -ENOMEM in alb_upper_dev_walk to stop walking, print some warn
information when failed to allocate memory for vlan tags in
bond_verify_device_path.

I also think that the following function calls
netdev_walk_all_upper_dev_rcu
---->>>alb_upper_dev_walk
---------->>>bond_verify_device_path

quoted

 From this way, "end device" can eventually be obtained from "start device"

in bond_verify_device_path, IS_ERR(tags) could be instead of
IS_ERR_OR_NULL(tags) in alb_upper_dev_walk.

Signed-off-by: Zhengchao Shao <redacted>
---
v4: print information instead of warn
v3: return -ENOMEM instead of zero to stop walk
v2: use WARN_ON_ONCE instead of WARN_ON
---
  drivers/net/bonding/bond_alb.c  | 3 ++-
  drivers/net/bonding/bond_main.c | 5 ++++-
  2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
index dc2c7b979656..7edf0fd58c34 100644
--- a/drivers/net/bonding/bond_alb.c
+++ b/drivers/net/bonding/bond_alb.c

@@ -985,7 +985,8 @@ static int alb_upper_dev_walk(struct net_device *upper,
  	if (netif_is_macvlan(upper) && !strict_match) {
  		tags = bond_verify_device_path(bond->dev, upper, 0);
  		if (IS_ERR_OR_NULL(tags))
-			BUG();
+			return -ENOMEM;
+
  		alb_send_lp_vid(slave, upper->dev_addr,
  				tags[0].vlan_proto, tags[0].vlan_id);
  		kfree(tags);

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 51d47eda1c87..1a40bd08f984 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c

@@ -2967,8 +2967,11 @@ struct bond_vlan_tag *bond_verify_device_path(struct net_device *start_dev,
  
  	if (start_dev == end_dev) {
  		tags = kcalloc(level + 1, sizeof(*tags), GFP_ATOMIC);
-		if (!tags)
+		if (!tags) {
+			net_err_ratelimited("%s: %s: Failed to allocate tags\n",
+					    __func__, start_dev->name);

I'm sorry for the repeated back and forth, but checkpatch points out
that the above warning adds little value: if the memory allocation
fails, the mm layer will emit a lot warning comprising the backtrace.

I suggest to drop it, thanks!

Thank you for your advice. And I will send v5 later.

Zhengchao Shao

Paolo