On Thu, Jan 28, 2021 at 5:01 PM Eric Dumazet <[email protected]> wrote:
>
>
>
> On 1/28/21 8:23 AM, Dmitry Vyukov wrote:
> > On Thu, Jan 28, 2021 at 3:43 AM Hillf Danton <[email protected]> wrote:
> >>
> >> Init the u64 stats in order to avoid the lockdep prints on the 32bit
> >> hardware like
> >
> > FTR this is not just to avoid lockdep prints, but also to prevent very
> > real stalls in production.
>
> Are you sure ?
>
> > u64_stats_init initializes seqlock, if the uninitialized
> > selock->sequence would be odd, the kernel will stall.
>
> Normally the whole netdev structure is zeroed when allocated,
> this is done in alloc_netdev_mqs()
>
> p = kvzalloc(alloc_size, GFP_KERNEL | __GFP_RETRY_MAYFAIL);
>
> So unless kvzalloc() has been changed recently to inject random data
> instead of 0, this bug is really about lockdep only.
You are right, I missed that the object is zero-initialized. Then it's
only a latent bug (if e.g. seqcount_init initializes count to an odd
value).
> > Maintainers, please send this upstream on your earliest convenience,
> > this breaks all 32-bit arches for testing purposes.
> >
> > Thanks
> >
> >> INFO: trying to register non-static key.
> >> the code is fine but needs lockdep annotation.
> >> turning off the locking correctness validator.
> >> CPU: 0 PID: 4695 Comm: syz-executor.0 Not tainted 5.11.0-rc5-syzkaller #0
> >> Hardware name: ARM-Versatile Express
> >> Backtrace:
> >> [<826fc5b8>] (dump_backtrace) from [<826fc82c>] (show_stack+0x18/0x1c
> >> arch/arm/kernel/traps.c:252)
> >> [<826fc814>] (show_stack) from [<8270d1f8>] (__dump_stack
> >> lib/dump_stack.c:79 [inline])
> >> [<826fc814>] (show_stack) from [<8270d1f8>] (dump_stack+0xa8/0xc8
> >> lib/dump_stack.c:120)
> >> [<8270d150>] (dump_stack) from [<802bf9c0>] (assign_lock_key
> >> kernel/locking/lockdep.c:935 [inline])
> >> [<8270d150>] (dump_stack) from [<802bf9c0>]
> >> (register_lock_class+0xabc/0xb68 kernel/locking/lockdep.c:1247)
> >> [<802bef04>] (register_lock_class) from [<802baa2c>]
> >> (__lock_acquire+0x84/0x32d4 kernel/locking/lockdep.c:4711)
> >> [<802ba9a8>] (__lock_acquire) from [<802be840>]
> >> (lock_acquire.part.0+0xf0/0x554 kernel/locking/lockdep.c:5442)
> >> [<802be750>] (lock_acquire.part.0) from [<802bed10>]
> >> (lock_acquire+0x6c/0x74 kernel/locking/lockdep.c:5415)
> >> [<802beca4>] (lock_acquire) from [<81560548>]
> >> (seqcount_lockdep_reader_access include/linux/seqlock.h:103 [inline])
> >> [<802beca4>] (lock_acquire) from [<81560548>] (__u64_stats_fetch_begin
> >> include/linux/u64_stats_sync.h:164 [inline])
> >> [<802beca4>] (lock_acquire) from [<81560548>] (u64_stats_fetch_begin
> >> include/linux/u64_stats_sync.h:175 [inline])
> >> [<802beca4>] (lock_acquire) from [<81560548>] (nsim_get_stats64+0xdc/0xf0
> >> drivers/net/netdevsim/netdev.c:70)
> >> [<8156046c>] (nsim_get_stats64) from [<81e2efa0>]
> >> (dev_get_stats+0x44/0xd0 net/core/dev.c:10405)
> >> [<81e2ef5c>] (dev_get_stats) from [<81e53204>]
> >> (rtnl_fill_stats+0x38/0x120 net/core/rtnetlink.c:1211)
> >> [<81e531cc>] (rtnl_fill_stats) from [<81e59d58>]
> >> (rtnl_fill_ifinfo+0x6d4/0x148c net/core/rtnetlink.c:1783)
> >> [<81e59684>] (rtnl_fill_ifinfo) from [<81e5ceb4>]
> >> (rtmsg_ifinfo_build_skb+0x9c/0x108 net/core/rtnetlink.c:3798)
> >> [<81e5ce18>] (rtmsg_ifinfo_build_skb) from [<81e5d0ac>]
> >> (rtmsg_ifinfo_event net/core/rtnetlink.c:3830 [inline])
> >> [<81e5ce18>] (rtmsg_ifinfo_build_skb) from [<81e5d0ac>]
> >> (rtmsg_ifinfo_event net/core/rtnetlink.c:3821 [inline])
> >> [<81e5ce18>] (rtmsg_ifinfo_build_skb) from [<81e5d0ac>]
> >> (rtmsg_ifinfo+0x44/0x70 net/core/rtnetlink.c:3839)
> >> [<81e5d068>] (rtmsg_ifinfo) from [<81e45c2c>]
> >> (register_netdevice+0x664/0x68c net/core/dev.c:10103)
> >> [<81e455c8>] (register_netdevice) from [<815608bc>]
> >> (nsim_create+0xf8/0x124 drivers/net/netdevsim/netdev.c:317)
> >> [<815607c4>] (nsim_create) from [<81561184>]
> >> (__nsim_dev_port_add+0x108/0x188 drivers/net/netdevsim/dev.c:941)
> >> [<8156107c>] (__nsim_dev_port_add) from [<815620d8>]
> >> (nsim_dev_port_add_all drivers/net/netdevsim/dev.c:990 [inline])
> >> [<8156107c>] (__nsim_dev_port_add) from [<815620d8>]
> >> (nsim_dev_probe+0x5cc/0x750 drivers/net/netdevsim/dev.c:1119)
> >> [<81561b0c>] (nsim_dev_probe) from [<815661dc>] (nsim_bus_probe+0x10/0x14
> >> drivers/net/netdevsim/bus.c:287)
> >> [<815661cc>] (nsim_bus_probe) from [<811724c0>] (really_probe+0x100/0x50c
> >> drivers/base/dd.c:554)
> >> [<811723c0>] (really_probe) from [<811729c4>]
> >> (driver_probe_device+0xf8/0x1c8 drivers/base/dd.c:740)
> >> [<811728cc>] (driver_probe_device) from [<81172fe4>]
> >> (__device_attach_driver+0x8c/0xf0 drivers/base/dd.c:846)
> >> [<81172f58>] (__device_attach_driver) from [<8116fee0>]
> >> (bus_for_each_drv+0x88/0xd8 drivers/base/bus.c:431)
> >> [<8116fe58>] (bus_for_each_drv) from [<81172c6c>]
> >> (__device_attach+0xdc/0x1d0 drivers/base/dd.c:914)
> >> [<81172b90>] (__device_attach) from [<8117305c>]
> >> (device_initial_probe+0x14/0x18 drivers/base/dd.c:961)
> >> [<81173048>] (device_initial_probe) from [<81171358>]
> >> (bus_probe_device+0x90/0x98 drivers/base/bus.c:491)
> >> [<811712c8>] (bus_probe_device) from [<8116e77c>] (device_add+0x320/0x824
> >> drivers/base/core.c:3109)
> >> [<8116e45c>] (device_add) from [<8116ec9c>] (device_register+0x1c/0x20
> >> drivers/base/core.c:3182)
> >> [<8116ec80>] (device_register) from [<81566710>] (nsim_bus_dev_new
> >> drivers/net/netdevsim/bus.c:336 [inline])
> >> [<8116ec80>] (device_register) from [<81566710>]
> >> (new_device_store+0x178/0x208 drivers/net/netdevsim/bus.c:215)
> >> [<81566598>] (new_device_store) from [<8116fcb4>]
> >> (bus_attr_store+0x2c/0x38 drivers/base/bus.c:122)
> >> [<8116fc88>] (bus_attr_store) from [<805b4b8c>] (sysfs_kf_write+0x48/0x54
> >> fs/sysfs/file.c:139)
> >> [<805b4b44>] (sysfs_kf_write) from [<805b3c90>]
> >> (kernfs_fop_write_iter+0x128/0x1ec fs/kernfs/file.c:296)
> >> [<805b3b68>] (kernfs_fop_write_iter) from [<804d22fc>] (call_write_iter
> >> include/linux/fs.h:1901 [inline])
> >> [<805b3b68>] (kernfs_fop_write_iter) from [<804d22fc>] (new_sync_write
> >> fs/read_write.c:518 [inline])
> >> [<805b3b68>] (kernfs_fop_write_iter) from [<804d22fc>]
> >> (vfs_write+0x3dc/0x57c fs/read_write.c:605)
> >> [<804d1f20>] (vfs_write) from [<804d2604>] (ksys_write+0x68/0xec
> >> fs/read_write.c:658)
> >> [<804d259c>] (ksys_write) from [<804d2698>] (__do_sys_write
> >> fs/read_write.c:670 [inline])
> >> [<804d259c>] (ksys_write) from [<804d2698>] (sys_write+0x10/0x14
> >> fs/read_write.c:667)
> >> [<804d2688>] (sys_write) from [<80200060>] (ret_fast_syscall+0x0/0x2c
> >> arch/arm/mm/proc-v7.S:64)
> >>
> >> Fixes: 83c9e13aa39a ("netdevsim: add software driver for testing offloads")
> >> Reported-by: [email protected]
> >> Tested-by: Dmitry Vyukov <[email protected]>
> >> Cc: Jakub Kicinski <[email protected]>
> >> Cc: Simon Horman <[email protected]>
> >> Cc: Quentin Monnet <[email protected]>
> >> Cc: Daniel Borkmann <[email protected]>
> >> Signed-off-by: Hillf Danton <[email protected]>
> >> ---
> >>
> >> --- a/drivers/net/netdevsim/netdev.c
> >> +++ b/drivers/net/netdevsim/netdev.c
> >> @@ -296,6 +296,7 @@ nsim_create(struct nsim_dev *nsim_dev, s
> >> dev_net_set(dev, nsim_dev_net(nsim_dev));
> >> ns = netdev_priv(dev);
> >> ns->netdev = dev;
> >> + u64_stats_init(&ns->syncp);
> >> ns->nsim_dev = nsim_dev;
> >> ns->nsim_dev_port = nsim_dev_port;
> >> ns->nsim_bus_dev = nsim_dev->nsim_bus_dev;
