Re: Regression with 5dcd8400884c ("macsec: missing dev_put() on error in macsec_newlink()")

[Sabrina Dubroca]

Hello Laura,

2018-04-14, 10:56:55 -0700, Laura Abbott wrote:
> Hi,
> 
> Fedora got a bug report of a regression when trying to remove the
> the macsec module (https://bugzilla.redhat.com/show_bug.cgi?id=1566410).
> I did a bisect and found
> 
> commit 5dcd8400884cc4a043a6d4617e042489e5d566a9
> Author: Dan Carpenter 
> Date:   Wed Mar 21 11:09:01 2018 +0300
> 
> macsec: missing dev_put() on error in macsec_newlink()
> We moved the dev_hold(real_dev); call earlier in the function but forgot
> to update the error paths.
> Fixes: 0759e552bce7 ("macsec: fix negative refcnt on parent link")
> Signed-off-by: Dan Carpenter 
> Signed-off-by: David S. Miller 
> 
> The script I used for testing based on the reporter is attached. It
> looks like modprobe is stuck in the D state. Any idea?

I don't think that reference was actually leaked. It gets released in
macsec_free_netdev() when the device is deleted.

modprobe getting stuck is just a side-effect of the refcount going
negative on the parent device, since removing the module needs to take
the lock that is held by device deletion.

I'll send a revert tomorrow.

Thanks for the report,

-- 
Sabrina

Re: Regression with 5dcd8400884c ("macsec: missing dev_put() on error in macsec_newlink()")

[Sabrina Dubroca]

Hello Laura,

2018-04-14, 10:56:55 -0700, Laura Abbott wrote:
> Hi,
> 
> Fedora got a bug report of a regression when trying to remove the
> the macsec module (https://bugzilla.redhat.com/show_bug.cgi?id=1566410).
> I did a bisect and found
> 
> commit 5dcd8400884cc4a043a6d4617e042489e5d566a9
> Author: Dan Carpenter 
> Date:   Wed Mar 21 11:09:01 2018 +0300
> 
> macsec: missing dev_put() on error in macsec_newlink()
> We moved the dev_hold(real_dev); call earlier in the function but forgot
> to update the error paths.
> Fixes: 0759e552bce7 ("macsec: fix negative refcnt on parent link")
> Signed-off-by: Dan Carpenter 
> Signed-off-by: David S. Miller 
> 
> The script I used for testing based on the reporter is attached. It
> looks like modprobe is stuck in the D state. Any idea?

I don't think that reference was actually leaked. It gets released in
macsec_free_netdev() when the device is deleted.

modprobe getting stuck is just a side-effect of the refcount going
negative on the parent device, since removing the module needs to take
the lock that is held by device deletion.

I'll send a revert tomorrow.

Thanks for the report,

-- 
Sabrina