[PATCH net-next] xfrm: use net device refcount tracker helpers

From: Eric Dumazet <redacted>

xfrm4_fill_dst() and xfrm6_fill_dst() build dst,
getting a device reference that will likely be released
by standard dst_release() code.

We have to track these references or risk a warning if
CONFIG_NET_DEV_REFCNT_TRACKER=y

Note to XFRM maintainers :

Error path in xfrm6_fill_dst() releases the reference,
but does not clear xdst->u.dst.dev, so I wonder
if this could lead to double dev_put() in some cases,
where a dst_release() _is_ called by the callers in their
error path.

This extra dev_put() was added in commit 84c4a9dfbf430 ("xfrm6:
release dev before returning error")

Fixes: 9038c320001d ("net: dst: add net device refcount tracking to dst_entry")
Signed-off-by: Eric Dumazet <redacted>
Cc: Cong Wang <redacted>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
---
 net/ipv4/xfrm4_policy.c | 2 +-
 net/ipv6/xfrm6_policy.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/xfrm4_policy.c b/net/ipv4/xfrm4_policy.c
index 9ebd54752e03b81a01f6c53cc17cebbccd928137..9e83bcb6bc99dd8cb7e71c9f1dbb5b7ae5570626 100644
--- a/net/ipv4/xfrm4_policy.c
+++ b/net/ipv4/xfrm4_policy.c

@@ -77,7 +77,7 @@ static int xfrm4_fill_dst(struct xfrm_dst *xdst, struct net_device *dev,
 	xdst->u.rt.rt_iif = fl4->flowi4_iif;
 
 	xdst->u.dst.dev = dev;
-	dev_hold(dev);
+	dev_hold_track(dev, &xdst->u.dst.dev_tracker, GFP_ATOMIC);
 
 	/* Sheit... I remember I did this right. Apparently,
 	 * it was magically lost, so this code needs audit */

diff --git a/net/ipv6/xfrm6_policy.c b/net/ipv6/xfrm6_policy.c
index af7a4b8b1e9c4a46a0b0cf4245a981efa24b9152..fad687ee6dd81af9ee3591eb2333cfed8ceae8ce 100644
--- a/net/ipv6/xfrm6_policy.c
+++ b/net/ipv6/xfrm6_policy.c

@@ -74,11 +74,11 @@ static int xfrm6_fill_dst(struct xfrm_dst *xdst, struct net_device *dev,
 	struct rt6_info *rt = (struct rt6_info *)xdst->route;
 
 	xdst->u.dst.dev = dev;
-	dev_hold(dev);
+	dev_hold_track(dev, &xdst->u.dst.dev_tracker, GFP_ATOMIC);
 
 	xdst->u.rt6.rt6i_idev = in6_dev_get(dev);
 	if (!xdst->u.rt6.rt6i_idev) {
-		dev_put(dev);
+		dev_put_track(dev, &xdst->u.dst.dev_tracker);
 		return -ENODEV;
 	}
 

-- 
2.34.1.400.ga245620fadb-goog

On Tue, Dec 07, 2021 at 11:32:03AM -0800, Eric Dumazet wrote:

From: Eric Dumazet <redacted>

xfrm4_fill_dst() and xfrm6_fill_dst() build dst,
getting a device reference that will likely be released
by standard dst_release() code.

We have to track these references or risk a warning if
CONFIG_NET_DEV_REFCNT_TRACKER=y

Note to XFRM maintainers :

Error path in xfrm6_fill_dst() releases the reference,
but does not clear xdst->u.dst.dev, so I wonder
if this could lead to double dev_put() in some cases,
where a dst_release() _is_ called by the callers in their
error path.

Yes, looks like it can, so this should be fixed.

This extra dev_put() was added in commit 84c4a9dfbf430 ("xfrm6:
release dev before returning error")

Fixes: 9038c320001d ("net: dst: add net device refcount tracking to dst_entry")
Signed-off-by: Eric Dumazet <redacted>
Cc: Cong Wang <redacted>
Cc: Steffen Klassert <steffen.klassert@secunet.com>

As the refcount tracking infrastructure is not yet in ipsec-next:

Acked-by: Steffen Klassert <steffen.klassert@secunet.com>

Thanks!

On Thu, 9 Dec 2021 10:20:36 +0100 Steffen Klassert wrote:

On Tue, Dec 07, 2021 at 11:32:03AM -0800, Eric Dumazet wrote:

quoted

From: Eric Dumazet <redacted>
release dev before returning error")

Fixes: 9038c320001d ("net: dst: add net device refcount tracking to dst_entry")
Signed-off-by: Eric Dumazet <redacted>
Cc: Cong Wang <redacted>
Cc: Steffen Klassert <steffen.klassert@secunet.com>  

As the refcount tracking infrastructure is not yet in ipsec-next:

Acked-by: Steffen Klassert <steffen.klassert@secunet.com>

Applied, thanks!

Hello:

This patch was applied to netdev/net-next.git (master)
by Jakub Kicinski [off-list ref]:

On Tue,  7 Dec 2021 11:32:03 -0800 you wrote:

From: Eric Dumazet <redacted>

xfrm4_fill_dst() and xfrm6_fill_dst() build dst,
getting a device reference that will likely be released
by standard dst_release() code.

We have to track these references or risk a warning if
CONFIG_NET_DEV_REFCNT_TRACKER=y

[...]

Here is the summary with links:
  - [net-next] xfrm: use net device refcount tracker helpers
    https://git.kernel.org/netdev/net-next/c/4177e4960594

You are awesome, thank you!
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