Re: [PATCH net-next] genetlink: fix policy dump for dumps

[Leon Romanovsky <leon@kernel.org>]

On Wed, Nov 09, 2022 at 07:46:34PM +0200, Leon Romanovsky wrote:
> On Tue, Nov 08, 2022 at 12:40:41PM -0800, Jakub Kicinski wrote:
> > Jonathan reports crashes when running net-next in Meta's fleet.
> 
> I experience these crashes too.
> 
> > Stats collection uses ethtool -I which does a per-op policy dump
> > to check if stats are supported. We don't initialize the dumpit
> > information if doit succeeds due to evaluation short-circuiting.
> > 
> > The crash may look like this:
> > 
> >    BUG: kernel NULL pointer dereference, address: 0000000000000cc0
> >    RIP: 0010:netlink_policy_dump_add_policy+0x174/0x2a0
> >      ctrl_dumppolicy_start+0x19f/0x2f0
> >      genl_start+0xe7/0x140
> > 
> > Or we may trigger a warning:
> > 
> >    WARNING: CPU: 1 PID: 785 at net/netlink/policy.c:87 netlink_policy_dump_get_policy_idx+0x79/0x80
> >    RIP: 0010:netlink_policy_dump_get_policy_idx+0x79/0x80
> >      ctrl_dumppolicy_put_op+0x214/0x360
> > 
> > depending on what garbage we pick up from the stack.
> > 
> > Reported-by: Jonathan Lemon <bsd@meta.com>
> > Fixes: 26588edbef60 ("genetlink: support split policies in ctrl_dumppolicy_put_op()")
> > Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> > ---
> > CC: jacob.e.keller@intel.com
> > ---
> >  net/netlink/genetlink.c | 12 ++++++------
> >  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> I added your updated patch to my CI run. Unfortunately, the regression
> system is overloaded due to nightly regression so won't be able to get
> results in sensible time frame.
> 

Thanks,
Tested-by: Leon Romanovsky <leonro@nvidia.com>