[linux-rt-devel:linux-5.14.y-rt-rebase 143/245] kernel/futex.c:1887:3: warning: Value stored to 'ret' is never read [clang-analyzer-deadcode.DeadStores]

From: kernel test robot
Date: Tue Aug 17 2021 - 02:19:28 EST

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tree: https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-5.14.y-rt-rebase
head: 0eead4e5a60cb716ec911a552787a69332cf6943
commit: 7384201f9701c226cb1dd04cf76c12c33762bb30 [143/245] futex: Validate waiter correctly in futex_proxy_trylock_atomic()
config: mips-randconfig-c004-20210816 (attached as .config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 44d0a99a12ec7ead4d2f5ef649ba05b40f6d463d)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# install mips cross compiling tool for clang build
# apt-get install binutils-mips-linux-gnu
# https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/commit/?id=7384201f9701c226cb1dd04cf76c12c33762bb30
git remote add linux-rt-devel https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git
git fetch --no-tags linux-rt-devel linux-5.14.y-rt-rebase
git checkout 7384201f9701c226cb1dd04cf76c12c33762bb30
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=mips clang-analyzer

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>

clang-analyzer warnings: (new ones prefixed by >>)
^
kernel/futex.c:3714:6: note: Assuming the condition is false
if (op & FUTEX_CLOCK_REALTIME) {
^~~~~~~~~~~~~~~~~~~~~~~~~
kernel/futex.c:3714:2: note: Taking false branch
if (op & FUTEX_CLOCK_REALTIME) {
^
kernel/futex.c:3721:2: note: 'Default' branch taken. Execution continues on line 3732
switch (cmd) {
^
kernel/futex.c:3732:2: note: Control jumps to 'case 5:' at line 3747
switch (cmd) {
^
kernel/futex.c:3748:10: note: Calling 'futex_wake_op'
return futex_wake_op(uaddr, flags, uaddr2, val, val2, val3);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/futex.c:1699:2: note: Taking false branch
if (unlikely(ret != 0))
^
kernel/futex.c:1702:2: note: Taking false branch
if (unlikely(ret != 0))
^
kernel/futex.c:1710:11: note: Calling 'futex_atomic_op_inuser'
op_ret = futex_atomic_op_inuser(op, uaddr2);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/futex.c:1643:6: note: 'oldval' declared without an initial value
int oldval, ret;
^~~~~~
kernel/futex.c:1645:6: note: Assuming the condition is false
if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28)) {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/futex.c:1645:2: note: Taking false branch
if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28)) {
^
kernel/futex.c:1660:8: note: Calling 'arch_futex_atomic_op_inuser'
ret = arch_futex_atomic_op_inuser(op, oparg, &oldval, uaddr);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/mips/include/asm/futex.h:92:7: note: Assuming the condition is false
if (!access_ok(uaddr, sizeof(u32)))
^
arch/mips/include/asm/uaccess.h:88:2: note: expanded from macro 'access_ok'
likely(__access_ok((addr), (size)))
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler.h:77:38: note: expanded from macro 'likely'
# define likely(x) __builtin_expect(!!(x), 1)
^~~~
arch/mips/include/asm/futex.h:92:2: note: Taking false branch
if (!access_ok(uaddr, sizeof(u32)))
^
arch/mips/include/asm/futex.h:95:2: note: Control jumps to 'case 3:' at line 108
switch (op) {
^
arch/mips/include/asm/futex.h:109:3: note: Left side of '&&' is true
__futex_atomic_op("and $1, %1, %z5",
^
arch/mips/include/asm/futex.h:24:6: note: expanded from macro '__futex_atomic_op'
if (cpu_has_llsc && IS_ENABLED(CONFIG_WAR_R10000_LLSC)) { \
^
arch/mips/include/asm/mach-rc32434/cpu-feature-overrides.h:34:24: note: expanded from macro 'cpu_has_llsc'
#define cpu_has_llsc 1
^
arch/mips/include/asm/futex.h:109:3: note: Taking false branch
__futex_atomic_op("and $1, %1, %z5",
^
arch/mips/include/asm/futex.h:24:2: note: expanded from macro '__futex_atomic_op'
if (cpu_has_llsc && IS_ENABLED(CONFIG_WAR_R10000_LLSC)) { \
^
arch/mips/include/asm/futex.h:109:3: note: Taking true branch
__futex_atomic_op("and $1, %1, %z5",
^
arch/mips/include/asm/futex.h:53:9: note: expanded from macro '__futex_atomic_op'
} else if (cpu_has_llsc) { \
^
arch/mips/include/asm/futex.h:111:3: note: Execution continues on line 120
break;
^
arch/mips/include/asm/futex.h:120:6: note: Assuming 'ret' is not equal to 0
if (!ret)
^~~~
arch/mips/include/asm/futex.h:120:2: note: Taking false branch
if (!ret)
^
arch/mips/include/asm/futex.h:123:2: note: Returning without writing to '*oval'
return ret;
^
kernel/futex.c:1660:8: note: Returning from 'arch_futex_atomic_op_inuser'
ret = arch_futex_atomic_op_inuser(op, oparg, &oldval, uaddr);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/futex.c:1662:6: note: Assuming 'ret' is 0
if (ret)
^~~
kernel/futex.c:1662:2: note: Taking false branch
if (ret)
^
kernel/futex.c:1665:2: note: Control jumps to 'case 4:' at line 1676
switch (cmp) {
^
kernel/futex.c:1677:17: note: The left operand of '>' is a garbage value
return oldval > cmparg;
~~~~~~ ^
>> kernel/futex.c:1887:3: warning: Value stored to 'ret' is never read [clang-analyzer-deadcode.DeadStores]
ret = -EINVAL;
^ ~~~~~~~
kernel/futex.c:1887:3: note: Value stored to 'ret' is never read
ret = -EINVAL;
^ ~~~~~~~
Suppressed 3 warnings (3 in non-user code).
Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
3 warnings generated.
Suppressed 3 warnings (3 in non-user code).
Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
3 warnings generated.
Suppressed 3 warnings (3 in non-user code).
Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
5 warnings generated.
drivers/soundwire/stream.c:847:10: warning: Use of memory after it is freed [clang-analyzer-unix.Malloc]
kfree(bus->defer_msg.msg->buf);
^
drivers/soundwire/stream.c:1755:6: note: Assuming 'stream' is non-null
if (!stream) {
^~~~~~~
drivers/soundwire/stream.c:1755:2: note: Taking false branch
if (!stream) {
^
drivers/soundwire/stream.c:1762:6: note: Assuming field 'state' is equal to SDW_STREAM_ENABLED
if (stream->state != SDW_STREAM_ENABLED) {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/soundwire/stream.c:1762:2: note: Taking false branch
if (stream->state != SDW_STREAM_ENABLED) {
^
drivers/soundwire/stream.c:1769:8: note: Calling '_sdw_disable_stream'
ret = _sdw_disable_stream(stream);
^~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/soundwire/stream.c:1700:2: note: Left side of '&&' is false
list_for_each_entry(m_rt, &stream->master_list, stream_node) {
^
include/linux/list.h:628:13: note: expanded from macro 'list_for_each_entry'
for (pos = list_first_entry(head, typeof(*pos), member); \
^
include/linux/list.h:522:2: note: expanded from macro 'list_first_entry'
list_entry((ptr)->next, type, member)
^
include/linux/list.h:511:2: note: expanded from macro 'list_entry'
container_of(ptr, type, member)
^
include/linux/kernel.h:495:61: note: expanded from macro 'container_of'
BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
^
drivers/soundwire/stream.c:1700:2: note: Taking false branch
list_for_each_entry(m_rt, &stream->master_list, stream_node) {
^
include/linux/list.h:628:13: note: expanded from macro 'list_for_each_entry'
for (pos = list_first_entry(head, typeof(*pos), member); \
^
include/linux/list.h:522:2: note: expanded from macro 'list_first_entry'
list_entry((ptr)->next, type, member)
^
include/linux/list.h:511:2: note: expanded from macro 'list_entry'
container_of(ptr, type, member)
^
note: (skipping 2 expansions in backtrace; use -fmacro-backtrace-limit=0 to see all)
include/linux/compiler_types.h:328:2: note: expanded from macro 'compiletime_assert'
_compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
^
include/linux/compiler_types.h:316:2: note: expanded from macro '_compiletime_assert'
__compiletime_assert(condition, msg, prefix, suffix)
^
include/linux/compiler_types.h:308:3: note: expanded from macro '__compiletime_assert'
if (!(condition)) \
^
drivers/soundwire/stream.c:1700:2: note: Loop condition is false. Exiting loop
list_for_each_entry(m_rt, &stream->master_list, stream_node) {
^
include/linux/list.h:628:13: note: expanded from macro 'list_for_each_entry'
for (pos = list_first_entry(head, typeof(*pos), member); \
^
include/linux/list.h:522:2: note: expanded from macro 'list_first_entry'
list_entry((ptr)->next, type, member)
^
include/linux/list.h:511:2: note: expanded from macro 'list_entry'
container_of(ptr, type, member)
^
note: (skipping 2 expansions in backtrace; use -fmacro-backtrace-limit=0 to see all)
include/linux/compiler_types.h:328:2: note: expanded from macro 'compiletime_assert'
_compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
^
include/linux/compiler_types.h:316:2: note: expanded from macro '_compiletime_assert'
__compiletime_assert(condition, msg, prefix, suffix)
^
include/linux/compiler_types.h:306:2: note: expanded from macro '__compiletime_assert'
do { \
^
drivers/soundwire/stream.c:1700:2: note: Loop condition is false. Execution continues on line 1710
list_for_each_entry(m_rt, &stream->master_list, stream_node) {
^
include/linux/list.h:628:2: note: expanded from macro 'list_for_each_entry'
for (pos = list_first_entry(head, typeof(*pos), member); \
^
drivers/soundwire/stream.c:1712:2: note: Left side of '&&' is false
list_for_each_entry(m_rt, &stream->master_list, stream_node) {
^

vim +/ret +1887 kernel/futex.c

1825
1826 /**
1827 * futex_proxy_trylock_atomic() - Attempt an atomic lock for the top waiter
1828 * @pifutex: the user address of the to futex
1829 * @hb1: the from futex hash bucket, must be locked by the caller
1830 * @hb2: the to futex hash bucket, must be locked by the caller
1831 * @key1: the from futex key
1832 * @key2: the to futex key
1833 * @ps: address to store the pi_state pointer
1834 * @exiting: Pointer to store the task pointer of the owner task
1835 * which is in the middle of exiting
1836 * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0)
1837 *
1838 * Try and get the lock on behalf of the top waiter if we can do it atomically.
1839 * Wake the top waiter if we succeed. If the caller specified set_waiters,
1840 * then direct futex_lock_pi_atomic() to force setting the FUTEX_WAITERS bit.
1841 * hb1 and hb2 must be held by the caller.
1842 *
1843 * @exiting is only set when the return value is -EBUSY. If so, this holds
1844 * a refcount on the exiting task on return and the caller needs to drop it
1845 * after waiting for the exit to complete.
1846 *
1847 * Return:
1848 * - 0 - failed to acquire the lock atomically;
1849 * - >0 - acquired the lock, return value is vpid of the top_waiter
1850 * - <0 - error
1851 */
1852 static int
1853 futex_proxy_trylock_atomic(u32 __user *pifutex, struct futex_hash_bucket *hb1,
1854 struct futex_hash_bucket *hb2, union futex_key *key1,
1855 union futex_key *key2, struct futex_pi_state **ps,
1856 struct task_struct **exiting, int set_waiters)
1857 {
1858 struct futex_q *top_waiter = NULL;
1859 u32 curval;
1860 int ret, vpid;
1861
1862 if (get_futex_value_locked(&curval, pifutex))
1863 return -EFAULT;
1864
1865 if (unlikely(should_fail_futex(true)))
1866 return -EFAULT;
1867
1868 /*
1869 * Find the top_waiter and determine if there are additional waiters.
1870 * If the caller intends to requeue more than 1 waiter to pifutex,
1871 * force futex_lock_pi_atomic() to set the FUTEX_WAITERS bit now,
1872 * as we have means to handle the possible fault. If not, don't set
1873 * the bit unnecessarily as it will force the subsequent unlock to enter
1874 * the kernel.
1875 */
1876 top_waiter = futex_top_waiter(hb1, key1);
1877
1878 /* There are no waiters, nothing for us to do. */
1879 if (!top_waiter)
1880 return 0;
1881
1882 /*
1883 * Ensure that this is a waiter sitting in futex_wait_requeue_pi()
1884 * and waiting on the 'waitqueue' futex which is always !PI.
1885 */
1886 if (!top_waiter->rt_waiter || top_waiter->pi_state)
> 1887 ret = -EINVAL;
1888
1889 /* Ensure we requeue to the expected futex. */
1890 if (!match_futex(top_waiter->requeue_pi_key, key2))
1891 return -EINVAL;
1892
1893 /*
1894 * Try to take the lock for top_waiter. Set the FUTEX_WAITERS bit in
1895 * the contended case or if set_waiters is 1. The pi_state is returned
1896 * in ps in contended cases.
1897 */
1898 vpid = task_pid_vnr(top_waiter->task);
1899 ret = futex_lock_pi_atomic(pifutex, hb2, key2, ps, top_waiter->task,
1900 exiting, set_waiters);
1901 if (ret == 1) {
1902 requeue_pi_wake_futex(top_waiter, key2, hb2);
1903 return vpid;
1904 }
1905 return ret;
1906 }
1907

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx

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