linux.git/drivers/pps/kapi.c, branch v6.18.21

pps: fix warning in pps_register_cdev when register device fail

2025-09-06T14:00:40+00:00

Similar to previous commit 2a934fdb01db ("media: v4l2-dev: fix error
handling in __video_register_device()"), the release hook should be set
before device_register(). Otherwise, when device_register() return error
and put_device() try to callback the release function, the below warning
may happen.

  ------------[ cut here ]------------
  WARNING: CPU: 1 PID: 4760 at drivers/base/core.c:2567 device_release+0x1bd/0x240 drivers/base/core.c:2567
  Modules linked in:
  CPU: 1 UID: 0 PID: 4760 Comm: syz.4.914 Not tainted 6.17.0-rc3+ #1 NONE
  RIP: 0010:device_release+0x1bd/0x240 drivers/base/core.c:2567
  Call Trace:
   
   kobject_cleanup+0x136/0x410 lib/kobject.c:689
   kobject_release lib/kobject.c:720 [inline]
   kref_put include/linux/kref.h:65 [inline]
   kobject_put+0xe9/0x130 lib/kobject.c:737
   put_device+0x24/0x30 drivers/base/core.c:3797
   pps_register_cdev+0x2da/0x370 drivers/pps/pps.c:402
   pps_register_source+0x2f6/0x480 drivers/pps/kapi.c:108
   pps_tty_open+0x190/0x310 drivers/pps/clients/pps-ldisc.c:57
   tty_ldisc_open+0xa7/0x120 drivers/tty/tty_ldisc.c:432
   tty_set_ldisc+0x333/0x780 drivers/tty/tty_ldisc.c:563
   tiocsetd drivers/tty/tty_io.c:2429 [inline]
   tty_ioctl+0x5d1/0x1700 drivers/tty/tty_io.c:2728
   vfs_ioctl fs/ioctl.c:51 [inline]
   __do_sys_ioctl fs/ioctl.c:598 [inline]
   __se_sys_ioctl fs/ioctl.c:584 [inline]
   __x64_sys_ioctl+0x194/0x210 fs/ioctl.c:584
   do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
   do_syscall_64+0x5f/0x2a0 arch/x86/entry/syscall_64.c:94
   entry_SYSCALL_64_after_hwframe+0x76/0x7e
   

Before commit c79a39dc8d06 ("pps: Fix a use-after-free"),
pps_register_cdev() call device_create() to create pps->dev, which will
init dev->release to device_create_release(). Now the comment is outdated,
just remove it.

Thanks for the reminder from Calvin Owens, 'kfree_pps' should be removed
in pps_register_source() to avoid a double free in the failure case.

Link: https://lore.kernel.org/all/20250827065010.3208525-1-wangliang74@huawei.com/
Fixes: c79a39dc8d06 ("pps: Fix a use-after-free")
Signed-off-by: Wang Liang 
Reviewed-By: Calvin Owens 
Link: https://lore.kernel.org/r/20250830075023.3498174-1-wangliang74@huawei.com
Signed-off-by: Greg Kroah-Hartman

pps: Fix a use-after-free

2025-01-07T14:16:48+00:00

On a board running ntpd and gpsd, I'm seeing a consistent use-after-free
in sys_exit() from gpsd when rebooting:

    pps pps1: removed
    ------------[ cut here ]------------
    kobject: '(null)' (00000000db4bec24): is not initialized, yet kobject_put() is being called.
    WARNING: CPU: 2 PID: 440 at lib/kobject.c:734 kobject_put+0x120/0x150
    CPU: 2 UID: 299 PID: 440 Comm: gpsd Not tainted 6.11.0-rc6-00308-gb31c44928842 #1
    Hardware name: Raspberry Pi 4 Model B Rev 1.1 (DT)
    pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
    pc : kobject_put+0x120/0x150
    lr : kobject_put+0x120/0x150
    sp : ffffffc0803d3ae0
    x29: ffffffc0803d3ae0 x28: ffffff8042dc9738 x27: 0000000000000001
    x26: 0000000000000000 x25: ffffff8042dc9040 x24: ffffff8042dc9440
    x23: ffffff80402a4620 x22: ffffff8042ef4bd0 x21: ffffff80405cb600
    x20: 000000000008001b x19: ffffff8040b3b6e0 x18: 0000000000000000
    x17: 0000000000000000 x16: 0000000000000000 x15: 696e6920746f6e20
    x14: 7369203a29343263 x13: 205d303434542020 x12: 0000000000000000
    x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000
    x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
    x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000
    x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000
    Call trace:
     kobject_put+0x120/0x150
     cdev_put+0x20/0x3c
     __fput+0x2c4/0x2d8
     ____fput+0x1c/0x38
     task_work_run+0x70/0xfc
     do_exit+0x2a0/0x924
     do_group_exit+0x34/0x90
     get_signal+0x7fc/0x8c0
     do_signal+0x128/0x13b4
     do_notify_resume+0xdc/0x160
     el0_svc+0xd4/0xf8
     el0t_64_sync_handler+0x140/0x14c
     el0t_64_sync+0x190/0x194
    ---[ end trace 0000000000000000 ]---

...followed by more symptoms of corruption, with similar stacks:

    refcount_t: underflow; use-after-free.
    kernel BUG at lib/list_debug.c:62!
    Kernel panic - not syncing: Oops - BUG: Fatal exception

This happens because pps_device_destruct() frees the pps_device with the
embedded cdev immediately after calling cdev_del(), but, as the comment
above cdev_del() notes, fops for previously opened cdevs are still
callable even after cdev_del() returns. I think this bug has always
been there: I can't explain why it suddenly started happening every time
I reboot this particular board.

In commit d953e0e837e6 ("pps: Fix a use-after free bug when
unregistering a source."), George Spelvin suggested removing the
embedded cdev. That seems like the simplest way to fix this, so I've
implemented his suggestion, using __register_chrdev() with pps_idr
becoming the source of truth for which minor corresponds to which
device.

But now that pps_idr defines userspace visibility instead of cdev_add(),
we need to be sure the pps->dev refcount can't reach zero while
userspace can still find it again. So, the idr_remove() call moves to
pps_unregister_cdev(), and pps_idr now holds a reference to pps->dev.

    pps_core: source serial1 got cdev (251:1)
    <...>
    pps pps1: removed
    pps_core: unregistering pps1
    pps_core: deallocating pps1

Fixes: d953e0e837e6 ("pps: Fix a use-after free bug when unregistering a source.")
Cc: stable@vger.kernel.org
Signed-off-by: Calvin Owens 
Reviewed-by: Michal Schmidt 
Link: https://lore.kernel.org/r/a17975fd5ae99385791929e563f72564edbcf28f.1731383727.git.calvin@wbinvd.org
Signed-off-by: Greg Kroah-Hartman

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 61

2019-05-24T15:36:45+00:00

Based on 1 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license as published by
  the free software foundation either version 2 of the license or at
  your option any later version this program is distributed in the
  hope that it will be useful but without any warranty without even
  the implied warranty of merchantability or fitness for a particular
  purpose see the gnu general public license for more details you
  should have received a copy of the gnu general public license along
  with this program if not write to the free software foundation inc
  675 mass ave cambridge ma 02139 usa

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 441 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Michael Ellerman  (powerpc)
Reviewed-by: Richard Fontana 
Reviewed-by: Allison Randal 
Reviewed-by: Kate Stewart 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190520071858.739733335@linutronix.de
Signed-off-by: Greg Kroah-Hartman

pps: using ERR_PTR instead of NULL while pps_register_source fails

2018-11-27T09:05:36+00:00

pps_register_source() has keeps error codes in a local variable,
but it does not make use of the code. This patch let it return
the errcode in case of failure.

Suggested-by: Richard Cochran 
Signed-off-by: YueHaibing 
Acked-by: Rodolfo Giometti 
Signed-off-by: Greg Kroah-Hartman

ntp/pps: use y2038 safe types in pps_event_time

2015-10-01T16:59:16+00:00

The pps_event_time uses two 'timespec' structures internally, which
suffer from the y2038 problem. The uses of this structure are
fairly self-contained in the pps code, so this replaces them all at
once.

Unfortunately, this includes the sfc ethernet driver aside from the
pps subsystem, so we change that one as well. Both touch the
same data structure, and there probably is no good way to split
the patch into smaller units.

Acked-by: Richard Cochran 
Acked-by: David S. Miller 
Reviewed-by: Thomas Gleixner 
Signed-off-by: Arnd Bergmann 
Signed-off-by: John Stultz

pps: convert to idr_alloc()

2013-02-28T03:10:18+00:00

Convert to the much saner new idr interface.

Signed-off-by: Tejun Heo 
Cc: Rodolfo Giometti 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pps: default echo function

2011-11-02T23:07:02+00:00

A default echo function has been provided so it is no longer an error when
you specify PPS_ECHOASSERT or PPS_ECHOCLEAR without an explicit echo
function.  This allows some code re-use and also makes it easier to write
client drivers since the default echo function does not normally need to
change.

Signed-off-by: James Nuss 
Reviewed-by: Ben Gardiner 
Acked-by: Rodolfo Giometti 
Cc: Ricardo Martins 
Cc: Alexander Gordeev 
Cc: Igor Plyatov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pps: initialize ts_real properly

2011-02-25T23:07:37+00:00

Initialize ts_real.flags to fix compiler warning about possible
uninitialized use of this field.

Signed-off-by: Alexander Gordeev 
Cc: john stultz 
Cc: Rodolfo Giometti 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pps: add kernel consumer support

2011-01-13T16:03:21+00:00

Add an optional feature of PPSAPI, kernel consumer support, which uses the
added hardpps() function.

Signed-off-by: Alexander Gordeev 
Acked-by: Rodolfo Giometti 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pps: simplify conditions a bit

2011-01-13T16:03:20+00:00

Bitwise conjunction is distributive so we can simplify some conditions.

Signed-off-by: Alexander Gordeev 
Acked-by: Rodolfo Giometti 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds