Re: [PATCH v6 28/28] ntsync: No longer depend on BROKEN.

Re: [PATCH v6 28/28] ntsync: No longer depend on BROKEN.

[kernel test robot]

BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
In-Reply-To: <20241209185904.507350-29-zfigura@codeweavers.com>
References: <20241209185904.507350-29-zfigura@codeweavers.com>
TO: Elizabeth Figura <zfigura@codeweavers.com>
TO: Arnd Bergmann <arnd@arndb.de>
TO: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>
TO: Jonathan Corbet <corbet@lwn.net>
TO: Shuah Khan <skhan@linuxfoundation.org>
CC: linux-kernel@vger.kernel.org
CC: linux-api@vger.kernel.org
CC: wine-devel@winehq.org
CC: "André Almeida" <andrealmeid@igalia.com>
CC: Wolfram Sang <wsa-dev@sang-engineering.com>
CC: Arkadiusz Hiler <ahiler@codeweavers.com>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Andy Lutomirski <luto@kernel.org>
CC: linux-doc@vger.kernel.org
CC: linux-kselftest@vger.kernel.org
CC: Randy Dunlap <rdunlap@infradead.org>
CC: Ingo Molnar <mingo@redhat.com>
CC: Will Deacon <will@kernel.org>
CC: Waiman Long <longman@redhat.com>
CC: Boqun Feng <boqun.feng@gmail.com>
CC: Elizabeth Figura <zfigura@codeweavers.com>

Hi Elizabeth,

kernel test robot noticed the following build warnings:

[auto build test WARNING on cdd30ebb1b9f36159d66f088b61aee264e649d7a]

url:    https://github.com/intel-lab-lkp/linux/commits/Elizabeth-Figura/ntsync-Introduce-NTSYNC_IOC_WAIT_ANY/20241210-031155
base:   cdd30ebb1b9f36159d66f088b61aee264e649d7a
patch link:    https://lore.kernel.org/r/20241209185904.507350-29-zfigura%40codeweavers.com
patch subject: [PATCH v6 28/28] ntsync: No longer depend on BROKEN.
:::::: branch date: 2 days ago
:::::: commit date: 2 days ago
config: microblaze-randconfig-r073-20241210 (https://download.01.org/0day-ci/archive/20241212/202412120618.cqaPBBkL-lkp@intel.com/config)
compiler: microblaze-linux-gcc (GCC) 14.2.0

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202412120618.cqaPBBkL-lkp@intel.com/

smatch warnings:
drivers/misc/ntsync.c:1083 ntsync_wait_all() warn: potential spectre issue 'q->entries' [r] (local cap)

vim +1083 drivers/misc/ntsync.c

e48f54281af61c1 Elizabeth Figura 2024-12-09  1049  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1050  static int ntsync_wait_all(struct ntsync_device *dev, void __user *argp)
e48f54281af61c1 Elizabeth Figura 2024-12-09  1051  {
e48f54281af61c1 Elizabeth Figura 2024-12-09  1052  	struct ntsync_wait_args args;
e48f54281af61c1 Elizabeth Figura 2024-12-09  1053  	struct ntsync_q *q;
e48f54281af61c1 Elizabeth Figura 2024-12-09  1054  	int signaled;
e48f54281af61c1 Elizabeth Figura 2024-12-09  1055  	__u32 i;
e48f54281af61c1 Elizabeth Figura 2024-12-09  1056  	int ret;
e48f54281af61c1 Elizabeth Figura 2024-12-09  1057  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1058  	if (copy_from_user(&args, argp, sizeof(args)))
e48f54281af61c1 Elizabeth Figura 2024-12-09  1059  		return -EFAULT;
e48f54281af61c1 Elizabeth Figura 2024-12-09  1060  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1061  	ret = setup_wait(dev, &args, true, &q);
e48f54281af61c1 Elizabeth Figura 2024-12-09  1062  	if (ret < 0)
e48f54281af61c1 Elizabeth Figura 2024-12-09  1063  		return ret;
e48f54281af61c1 Elizabeth Figura 2024-12-09  1064  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1065  	/* queue ourselves */
e48f54281af61c1 Elizabeth Figura 2024-12-09  1066  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1067  	mutex_lock(&dev->wait_all_lock);
e48f54281af61c1 Elizabeth Figura 2024-12-09  1068  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1069  	for (i = 0; i < args.count; i++) {
e48f54281af61c1 Elizabeth Figura 2024-12-09  1070  		struct ntsync_q_entry *entry = &q->entries[i];
e48f54281af61c1 Elizabeth Figura 2024-12-09  1071  		struct ntsync_obj *obj = entry->obj;
e48f54281af61c1 Elizabeth Figura 2024-12-09  1072  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1073  		atomic_inc(&obj->all_hint);
e48f54281af61c1 Elizabeth Figura 2024-12-09  1074  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1075  		/*
e48f54281af61c1 Elizabeth Figura 2024-12-09  1076  		 * obj->all_waiters is protected by dev->wait_all_lock rather
e48f54281af61c1 Elizabeth Figura 2024-12-09  1077  		 * than obj->lock, so there is no need to acquire obj->lock
e48f54281af61c1 Elizabeth Figura 2024-12-09  1078  		 * here.
e48f54281af61c1 Elizabeth Figura 2024-12-09  1079  		 */
e48f54281af61c1 Elizabeth Figura 2024-12-09  1080  		list_add_tail(&entry->node, &obj->all_waiters);
e48f54281af61c1 Elizabeth Figura 2024-12-09  1081  	}
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1082  	if (args.alert) {
24ce2f869ab8577 Elizabeth Figura 2024-12-09 @1083  		struct ntsync_q_entry *entry = &q->entries[args.count];
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1084  		struct ntsync_obj *obj = entry->obj;
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1085  
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1086  		dev_lock_obj(dev, obj);
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1087  		list_add_tail(&entry->node, &obj->any_waiters);
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1088  		dev_unlock_obj(dev, obj);
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1089  	}
e48f54281af61c1 Elizabeth Figura 2024-12-09  1090  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1091  	/* check if we are already signaled */
e48f54281af61c1 Elizabeth Figura 2024-12-09  1092  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1093  	try_wake_all(dev, q, NULL);
e48f54281af61c1 Elizabeth Figura 2024-12-09  1094  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1095  	mutex_unlock(&dev->wait_all_lock);
e48f54281af61c1 Elizabeth Figura 2024-12-09  1096  
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1097  	/*
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1098  	 * Check if the alert event is signaled, making sure to do so only
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1099  	 * after checking if the other objects are signaled.
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1100  	 */
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1101  
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1102  	if (args.alert) {
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1103  		struct ntsync_obj *obj = q->entries[args.count].obj;
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1104  
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1105  		if (atomic_read(&q->signaled) == -1) {
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1106  			bool all = ntsync_lock_obj(dev, obj);
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1107  			try_wake_any_obj(obj);
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1108  			ntsync_unlock_obj(dev, obj, all);
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1109  		}
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1110  	}
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1111  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1112  	/* sleep */
e48f54281af61c1 Elizabeth Figura 2024-12-09  1113  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1114  	ret = ntsync_schedule(q, &args);
e48f54281af61c1 Elizabeth Figura 2024-12-09  1115  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1116  	/* and finally, unqueue */
e48f54281af61c1 Elizabeth Figura 2024-12-09  1117  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1118  	mutex_lock(&dev->wait_all_lock);
e48f54281af61c1 Elizabeth Figura 2024-12-09  1119  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1120  	for (i = 0; i < args.count; i++) {
e48f54281af61c1 Elizabeth Figura 2024-12-09  1121  		struct ntsync_q_entry *entry = &q->entries[i];
e48f54281af61c1 Elizabeth Figura 2024-12-09  1122  		struct ntsync_obj *obj = entry->obj;
e48f54281af61c1 Elizabeth Figura 2024-12-09  1123  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1124  		/*
e48f54281af61c1 Elizabeth Figura 2024-12-09  1125  		 * obj->all_waiters is protected by dev->wait_all_lock rather
e48f54281af61c1 Elizabeth Figura 2024-12-09  1126  		 * than obj->lock, so there is no need to acquire it here.
e48f54281af61c1 Elizabeth Figura 2024-12-09  1127  		 */
e48f54281af61c1 Elizabeth Figura 2024-12-09  1128  		list_del(&entry->node);
e48f54281af61c1 Elizabeth Figura 2024-12-09  1129  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1130  		atomic_dec(&obj->all_hint);
266531700b4e125 Elizabeth Figura 2024-12-09  1131  
266531700b4e125 Elizabeth Figura 2024-12-09  1132  		put_obj(obj);
266531700b4e125 Elizabeth Figura 2024-12-09  1133  	}
266531700b4e125 Elizabeth Figura 2024-12-09  1134  
e48f54281af61c1 Elizabeth Figura 2024-12-09  1135  	mutex_unlock(&dev->wait_all_lock);
e48f54281af61c1 Elizabeth Figura 2024-12-09  1136  
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1137  	if (args.alert) {
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1138  		struct ntsync_q_entry *entry = &q->entries[args.count];
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1139  		struct ntsync_obj *obj = entry->obj;
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1140  		bool all;
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1141  
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1142  		all = ntsync_lock_obj(dev, obj);
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1143  		list_del(&entry->node);
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1144  		ntsync_unlock_obj(dev, obj, all);
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1145  
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1146  		put_obj(obj);
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1147  	}
24ce2f869ab8577 Elizabeth Figura 2024-12-09  1148  
266531700b4e125 Elizabeth Figura 2024-12-09  1149  	signaled = atomic_read(&q->signaled);
266531700b4e125 Elizabeth Figura 2024-12-09  1150  	if (signaled != -1) {
266531700b4e125 Elizabeth Figura 2024-12-09  1151  		struct ntsync_wait_args __user *user_args = argp;
266531700b4e125 Elizabeth Figura 2024-12-09  1152  
266531700b4e125 Elizabeth Figura 2024-12-09  1153  		/* even if we caught a signal, we need to communicate success */
8492d88b692b51d Elizabeth Figura 2024-12-09  1154  		ret = q->ownerdead ? -EOWNERDEAD : 0;
266531700b4e125 Elizabeth Figura 2024-12-09  1155  
266531700b4e125 Elizabeth Figura 2024-12-09  1156  		if (put_user(signaled, &user_args->index))
266531700b4e125 Elizabeth Figura 2024-12-09  1157  			ret = -EFAULT;
266531700b4e125 Elizabeth Figura 2024-12-09  1158  	} else if (!ret) {
266531700b4e125 Elizabeth Figura 2024-12-09  1159  		ret = -ETIMEDOUT;
266531700b4e125 Elizabeth Figura 2024-12-09  1160  	}
266531700b4e125 Elizabeth Figura 2024-12-09  1161  
266531700b4e125 Elizabeth Figura 2024-12-09  1162  	kfree(q);
266531700b4e125 Elizabeth Figura 2024-12-09  1163  	return ret;
266531700b4e125 Elizabeth Figura 2024-12-09  1164  }
266531700b4e125 Elizabeth Figura 2024-12-09  1165  

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

[PATCH v6 00/28] NT synchronization primitive driver

[Elizabeth Figura]

This patch series implements a new char misc driver, /dev/ntsync, which is used
to implement Windows NT synchronization primitives.

NT synchronization primitives are unique in that the wait functions both are
vectored, operate on multiple types of object with different behaviour (mutex,
semaphore, event), and affect the state of the objects they wait on. This model
is not compatible with existing kernel synchronization objects or interfaces,
and therefore the ntsync driver implements its own wait queues and locking.

This patch series is rebased against the "char-misc-next" branch of
gregkh/char-misc.git.

== Background ==

The Wine project emulates the Windows API in user space. One particular part of
that API, namely the NT synchronization primitives, have historically been
implemented via RPC to a dedicated "kernel" process. However, more recent
applications use these APIs more strenuously, and the overhead of RPC has become
a bottleneck.

The NT synchronization APIs are too complex to implement on top of existing
primitives without sacrificing correctness. Certain operations, such as
NtPulseEvent() or the "wait-for-all" mode of NtWaitForMultipleObjects(), require
direct control over the underlying wait queue, and implementing a wait queue
sufficiently robust for Wine in user space is not possible. This proposed
driver, therefore, implements the problematic interfaces directly in the Linux
kernel.

This driver was presented at Linux Plumbers Conference 2023. For those further
interested in the history of synchronization in Wine and past attempts to solve
this problem in user space, a recording of the presentation can be viewed here:

    https://www.youtube.com/watch?v=NjU4nyWyhU8


== Performance ==

The performance measurements described below are copied from earlier versions of
the patch set. While some of the code has changed, I do not currently anticipate
that it has changed drastically enough to affect those measurements.

The gain in performance varies wildly depending on the application in question
and the user's hardware. For some games NT synchronization is not a bottleneck
and no change can be observed, but for others frame rate improvements of 50 to
150 percent are not atypical. The following table lists frame rate measurements
from a variety of games on a variety of hardware, taken by users Dmitry
Skvortsov, FuzzyQuils, OnMars, and myself:

Game                            Upstream        ntsync          improvement
===========================================================================
Anger Foot                       69              99              43%
Call of Juarez                   99.8           224.1           125%
Dirt 3                          110.6           860.7           678%
Forza Horizon 5                 108             160              48%
Lara Croft: Temple of Osiris    141             326             131%
Metro 2033                      164.4           199.2            21%
Resident Evil 2                  26              77             196%
The Crew                         26              51              96%
Tiny Tina's Wonderlands         130             360             177%
Total War Saga: Troy            109             146              34%
===========================================================================


== Patches ==

The intended semantics of the patches are broadly intended to match those of the
corresponding Windows functions. For those not already familiar with the Windows
functions (or their undocumented behaviour), patch 27/28 provides a detailed
specification, and individual patches also include a brief description of the
API they are implementing.

The patches making use of this driver in Wine can be retrieved or browsed here:

    https://repo.or.cz/wine/zf.git/shortlog/refs/heads/ntsync5

== Previous versions ==

No changes were made from v5 other than rebasing on top of the 6.13-rc1
char-misc-next tree.

I would like to repeat a question from the last round of review, though. Two
changes were suggested related to API design, which I did not make because the
APIs in question were already released in upstream Linux. However, the driver is
also completely nonfunctional and hidden behind BROKEN, so would this be
acceptable anyway? The changes in question are:

* rename NTSYNC_IOC_SEM_POST to NTSYNC_IOC_SEM_RELEASE (matching the NT
  terminology instead of POSIX),

* change object creation ioctls to return the fds directly in the return value
  instead of through the args struct. I would also still appreciate a
  clarification on the advice in [1], which is why I didn't do this in the first
  place.

  [1] https://docs.kernel.org/driver-api/ioctl.html#return-code

* Link to v5: https://lore.kernel.org/lkml/20240519202454.1192826-1-zfigura@codeweavers.com/
* Link to v4: https://lore.kernel.org/lkml/20240416010837.333694-1-zfigura@codeweavers.com/
* Link to v3: https://lore.kernel.org/lkml/20240329000621.148791-1-zfigura@codeweavers.com/
* Link to v2: https://lore.kernel.org/lkml/20240219223833.95710-1-zfigura@codeweavers.com/
* Link to v1: https://lore.kernel.org/lkml/20240214233645.9273-1-zfigura@codeweavers.com/
* Link to RFC v2: https://lore.kernel.org/lkml/20240131021356.10322-1-zfigura@codeweavers.com/
* Link to RFC v1: https://lore.kernel.org/lkml/20240124004028.16826-1-zfigura@codeweavers.com/

Elizabeth Figura (28):
  ntsync: Introduce NTSYNC_IOC_WAIT_ANY.
  ntsync: Introduce NTSYNC_IOC_WAIT_ALL.
  ntsync: Introduce NTSYNC_IOC_CREATE_MUTEX.
  ntsync: Introduce NTSYNC_IOC_MUTEX_UNLOCK.
  ntsync: Introduce NTSYNC_IOC_MUTEX_KILL.
  ntsync: Introduce NTSYNC_IOC_CREATE_EVENT.
  ntsync: Introduce NTSYNC_IOC_EVENT_SET.
  ntsync: Introduce NTSYNC_IOC_EVENT_RESET.
  ntsync: Introduce NTSYNC_IOC_EVENT_PULSE.
  ntsync: Introduce NTSYNC_IOC_SEM_READ.
  ntsync: Introduce NTSYNC_IOC_MUTEX_READ.
  ntsync: Introduce NTSYNC_IOC_EVENT_READ.
  ntsync: Introduce alertable waits.
  selftests: ntsync: Add some tests for semaphore state.
  selftests: ntsync: Add some tests for mutex state.
  selftests: ntsync: Add some tests for NTSYNC_IOC_WAIT_ANY.
  selftests: ntsync: Add some tests for NTSYNC_IOC_WAIT_ALL.
  selftests: ntsync: Add some tests for wakeup signaling with
    WINESYNC_IOC_WAIT_ANY.
  selftests: ntsync: Add some tests for wakeup signaling with
    WINESYNC_IOC_WAIT_ALL.
  selftests: ntsync: Add some tests for manual-reset event state.
  selftests: ntsync: Add some tests for auto-reset event state.
  selftests: ntsync: Add some tests for wakeup signaling with events.
  selftests: ntsync: Add tests for alertable waits.
  selftests: ntsync: Add some tests for wakeup signaling via alerts.
  selftests: ntsync: Add a stress test for contended waits.
  maintainers: Add an entry for ntsync.
  docs: ntsync: Add documentation for the ntsync uAPI.
  ntsync: No longer depend on BROKEN.

 Documentation/userspace-api/index.rst         |    1 +
 Documentation/userspace-api/ntsync.rst        |  398 +++++
 MAINTAINERS                                   |    9 +
 drivers/misc/Kconfig                          |    1 -
 drivers/misc/ntsync.c                         |  989 +++++++++++-
 include/uapi/linux/ntsync.h                   |   39 +
 tools/testing/selftests/Makefile              |    1 +
 .../selftests/drivers/ntsync/.gitignore       |    1 +
 .../testing/selftests/drivers/ntsync/Makefile |    7 +
 tools/testing/selftests/drivers/ntsync/config |    1 +
 .../testing/selftests/drivers/ntsync/ntsync.c | 1407 +++++++++++++++++
 11 files changed, 2850 insertions(+), 4 deletions(-)
 create mode 100644 Documentation/userspace-api/ntsync.rst
 create mode 100644 tools/testing/selftests/drivers/ntsync/.gitignore
 create mode 100644 tools/testing/selftests/drivers/ntsync/Makefile
 create mode 100644 tools/testing/selftests/drivers/ntsync/config
 create mode 100644 tools/testing/selftests/drivers/ntsync/ntsync.c


base-commit: cdd30ebb1b9f36159d66f088b61aee264e649d7a
-- 
2.45.2

[PATCH v6 28/28] ntsync: No longer depend on BROKEN.

[Elizabeth Figura]

f5b335dc025cfee90957efa90dc72fada0d5abb4 ("misc: ntsync: mark driver as "broken"
to prevent from building") was committed to avoid the driver being used while
only part of its functionality was released. Since the rest of the functionality
has now been committed, revert this.

Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com>
---
 drivers/misc/Kconfig | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 09cbe3f0ab1e..fb772bfe27c3 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -517,7 +517,6 @@ config OPEN_DICE
 
 config NTSYNC
 	tristate "NT synchronization primitive emulation"
-	depends on BROKEN
 	help
 	  This module provides kernel support for emulation of Windows NT
 	  synchronization primitives. It is not a hardware driver.
-- 
2.45.2

Re: [PATCH v6 28/28] ntsync: No longer depend on BROKEN.

[kernel test robot]

Hi Elizabeth,

kernel test robot noticed the following build errors:

[auto build test ERROR on cdd30ebb1b9f36159d66f088b61aee264e649d7a]

url:    https://github.com/intel-lab-lkp/linux/commits/Elizabeth-Figura/ntsync-Introduce-NTSYNC_IOC_WAIT_ANY/20241210-031155
base:   cdd30ebb1b9f36159d66f088b61aee264e649d7a
patch link:    https://lore.kernel.org/r/20241209185904.507350-29-zfigura%40codeweavers.com
patch subject: [PATCH v6 28/28] ntsync: No longer depend on BROKEN.
config: i386-randconfig-002-20241212 (https://download.01.org/0day-ci/archive/20241212/202412121219.EQhUbN0S-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241212/202412121219.EQhUbN0S-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202412121219.EQhUbN0S-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from include/linux/spinlock.h:60,
                    from include/linux/wait.h:9,
                    from include/linux/wait_bit.h:8,
                    from include/linux/fs.h:6,
                    from drivers/misc/ntsync.c:11:
   In function 'check_copy_size',
       inlined from 'copy_from_user' at include/linux/uaccess.h:207:7,
       inlined from 'setup_wait' at drivers/misc/ntsync.c:903:6:
>> include/linux/thread_info.h:259:25: error: call to '__bad_copy_to' declared with attribute error: copy destination size is too small
     259 |                         __bad_copy_to();
         |                         ^~~~~~~~~~~~~~~


vim +/__bad_copy_to +259 include/linux/thread_info.h

b0377fedb652808 Al Viro   2017-06-29  248  
9dd819a15162f8f Kees Cook 2019-09-25  249  static __always_inline __must_check bool
b0377fedb652808 Al Viro   2017-06-29  250  check_copy_size(const void *addr, size_t bytes, bool is_source)
b0377fedb652808 Al Viro   2017-06-29  251  {
c80d92fbb67b2c8 Kees Cook 2021-06-17  252  	int sz = __builtin_object_size(addr, 0);
b0377fedb652808 Al Viro   2017-06-29  253  	if (unlikely(sz >= 0 && sz < bytes)) {
b0377fedb652808 Al Viro   2017-06-29  254  		if (!__builtin_constant_p(bytes))
b0377fedb652808 Al Viro   2017-06-29  255  			copy_overflow(sz, bytes);
b0377fedb652808 Al Viro   2017-06-29  256  		else if (is_source)
b0377fedb652808 Al Viro   2017-06-29  257  			__bad_copy_from();
b0377fedb652808 Al Viro   2017-06-29  258  		else
b0377fedb652808 Al Viro   2017-06-29 @259  			__bad_copy_to();
b0377fedb652808 Al Viro   2017-06-29  260  		return false;
b0377fedb652808 Al Viro   2017-06-29  261  	}
6d13de1489b6bf5 Kees Cook 2019-12-04  262  	if (WARN_ON_ONCE(bytes > INT_MAX))
6d13de1489b6bf5 Kees Cook 2019-12-04  263  		return false;
b0377fedb652808 Al Viro   2017-06-29  264  	check_object_size(addr, bytes, is_source);
b0377fedb652808 Al Viro   2017-06-29  265  	return true;
b0377fedb652808 Al Viro   2017-06-29  266  }
b0377fedb652808 Al Viro   2017-06-29  267  

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v6 28/28] ntsync: No longer depend on BROKEN.

[Arnd Bergmann]

On Thu, Dec 12, 2024, at 05:52, kernel test robot wrote:
> Hi Elizabeth,
>
> kernel test robot noticed the following build errors:
>
> [auto build test ERROR on cdd30ebb1b9f36159d66f088b61aee264e649d7a]
>
> url:    
> https://github.com/intel-lab-lkp/linux/commits/Elizabeth-Figura/ntsync-Introduce-NTSYNC_IOC_WAIT_ANY/20241210-031155
> base:   cdd30ebb1b9f36159d66f088b61aee264e649d7a

> All errors (new ones prefixed by >>):
>
>    In file included from include/linux/spinlock.h:60,
>                     from include/linux/wait.h:9,
>                     from include/linux/wait_bit.h:8,
>                     from include/linux/fs.h:6,
>                     from drivers/misc/ntsync.c:11:
>    In function 'check_copy_size',
>        inlined from 'copy_from_user' at include/linux/uaccess.h:207:7,
>        inlined from 'setup_wait' at drivers/misc/ntsync.c:903:6:
>>> include/linux/thread_info.h:259:25: error: call to '__bad_copy_to' declared with attribute error: copy destination size is too small
>      259 |                         __bad_copy_to();
>          |                         ^~~~~~~~~~~~~~~

I looked up the function from the github URL above and found

	int fds[NTSYNC_MAX_WAIT_COUNT + 1];
	const __u32 count = args->count;
	struct ntsync_q *q;
	__u32 total_count;
	__u32 i, j;

	if (args->pad || (args->flags & ~NTSYNC_WAIT_REALTIME))
		return -EINVAL;

	if (args->count > NTSYNC_MAX_WAIT_COUNT)
		return -EINVAL;

	total_count = count;
	if (args->alert)
		total_count++;

	if (copy_from_user(fds, u64_to_user_ptr(args->objs),
			   array_size(count, sizeof(*fds))))
		return -EFAULT;

which looks correct to me, as it has appropriate
range checking on args->count, but I can see how
the warning may be a result of checking 'args->count'
instead of 'count'.

      Arnd