Re: fs_enet segfaults when adding network interface to bridge

[Laurent Pinchart <laurent.pinchart@tbox.biz>]

> > Hi everybody,
> >
> > I ran into a segfault in the fs_enet driver when adding the network
> > interface to an ethernet bridge. This only happens when the interface is
> > down.
> >
> > ----- Kernel version -----
> > Linux tbox-cp11 2.6.17-rc3-g7f02f290-dirty #549 Tue May 30 13:25:37 CEST
> > 2006 ppc unknown
> > (from main linux-2.6 git repository)
> > ----- End of kernel version -----
> >
> > ----- Oops report -----
> > Oops: kernel access of bad area, sig: 11 [#1]
> > NIP: C0109884 LR: C010D420 CTR: 00000000
> > REGS: c027d7f0 TRAP: 0300   Tainted: P       (2.6.17-rc3-g7f02f290-dirty)
> > MSR: 00009032 <EE,ME,IR,DR>  CR: 24000222  XER: 00000000
> > DAR: 00000140, DSISR: 20000000
> > TASK = c0851090[42] 'brctl' THREAD: c027c000
> > GPR00: C010D414 C027D8A0 C0851090 00000000 C027D8D0 FFFFFFFF F00000A0
> > EFFFFFFF GPR08: C026E380 C0210000 00000000 C0230000 C0210000 1001D150
> > 00FFE000 00000001 GPR16: FFFFFFFF 00000000 007FFF00 7FDD0AC0 00000000
> > 10072C94 7FDD0AD8 10072CA4 GPR24: 00000000 10000A48 00000000 C027D8D0
> > C027D8D0 C08A1A60 C027DC50 C08A1800 NIP [C0109884]
> > phy_ethtool_gset+0x0/0x48
> > LR [C010D420] fs_get_settings+0x34/0x48
> > Call Trace:
> > [C027D8A0] [C010D414] fs_get_settings+0x28/0x48 (unreliable)
> > [C027D8C0] [C013DDC0] dev_ethtool+0x9bc/0x13c8
> > [C027DC40] [C018CBC0] port_cost+0x58/0x108
> > [C027DCB0] [C018D3E8] br_add_if+0x174/0x2f4
> > [C027DCE0] [C018D9AC] add_del_if+0x94/0x98
> > [C027DD00] [C018DD68] br_dev_ioctl+0x70/0xae4
> > [C027DE00] [C013B42C] dev_ifsioc+0x17c/0x404
> > [C027DE20] [C013BA4C] dev_ioctl+0x398/0x4e8
> > [C027DEB0] [C012EEFC] sock_ioctl+0x154/0x220
> > [C027DEE0] [C0067164] do_ioctl+0x88/0x9c
> > [C027DEF0] [C0067230] vfs_ioctl+0xb8/0x3f0
> > [C027DF10] [C00675A8] sys_ioctl+0x40/0x74
> > [C027DF40] [C00040E0] ret_from_syscall+0x0/0x38
> > Instruction dump:
> > 7c0803a6 4e800020 2f800000 409eff78 4bffffb8 8804000e 2b800001 40bdff70
> > 3860ffea 4bffffd4 61200040 4bffff84 <81230140> 91240004 80030144 90040008
> > ----- End of oops report -----
> >
> > ----- Source lines -----
> > [C0109884] phy_ethtool_gset+0x0/0x48 (drivers/net/phy/phy.c:290)
> > [C010D414] fs_get_settings+0x28/0x48
> > (drivers/net/fs_enet/fs_enet-main.c:885) [C013DDC0]
> > dev_ethtool+0x9bc/0x13c8 (net/core/ethtool.c:122)
> > [C018CBC0] port_cost+0x58/0x108 (net/bridge/br_if.c:54)
> > ----- End of source lines -----
> >
> > phy_ethtool_gset segfaults when trying to access phydev->supported
> > because phydev is NULL.
> >
> > As I'm not familiar with the fs_enet driver, I'm looking for advices
> > regarding what to fix and how to fix it.
>
> IIRC, fs_enet got bound to phydev only being ->up. So in down state, phydev
> may be either null, or last assigned (need to have a look into source to
> tell for certain). So what is the proper behavior from your point of view?

I have no idea :-) What I know is that the driver should not segfault when 
asked to report the port speed. Either we should return an error or have the 
phy device bound to fs_enet at all time. It might also be a bridge issue, 
maybe the bridge code should turn the interface up before reading its speed. 
How do other ethernet drivers proceed ?

Laurent Pinchart