Re: drivers/hv/channel_mgmt.c:785:22: warning: Assigned value is garbage or undefined [clang-analyzer-core.uninitialized.Assign]

From: Chen, Rong A
Date: Wed Jul 28 2021 - 04:32:45 EST

Next message: Greg Kroah-Hartman: "Linux 4.4.277"
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In reply to: Haiyang Zhang: "RE: drivers/hv/channel_mgmt.c:785:22: warning: Assigned value is garbage or undefined [clang-analyzer-core.uninitialized.Assign]"
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On 7/27/2021 12:02 AM, Haiyang Zhang wrote:

-----Original Message-----
From: kernel test robot <rong.a.chen@xxxxxxxxx>
Sent: Sunday, July 25, 2021 11:43 PM
To: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
Cc: kbuild-all@xxxxxxxxxxxx; LKML <linux-kernel@xxxxxxxxxxxxxxx>; Wei
Liu <wei.liu@xxxxxxxxxx>; Michael Kelley <mikelley@xxxxxxxxxxxxx>
Subject: drivers/hv/channel_mgmt.c:785:22: warning: Assigned value is
garbage or undefined [clang-analyzer-core.uninitialized.Assign]

Hi Haiyang,

First bad commit (maybe != root cause):

tree:
https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.ke
rnel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git&d
ata=04%7C01%7Chaiyangz%40microsoft.com%7Cb1a7f087851b48a29bf308d94fe7849
0%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637628680585035821%7CUnkn
own%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLC
JXVCI6Mn0%3D%7C1000&sdata=6LkKnX%2BXhjmhh4m%2BzJ7y0JeQcwvwHw8NZP%2Bv
aXSdZV0%3D&reserved=0 master
head: d8079fac168168b25677dc16c00ffaf9fb7df723
commit: 7c9ff3deeee61b253715dcf968a6307af148c9b2 Drivers: hv: vmbus: Fix
duplicate CPU assignments within a device
date: 6 days ago
:::::: branch date: 11 hours ago
:::::: commit date: 6 days ago
config: x86_64-randconfig-c001-20210725 (attached as .config)
compiler: clang version 13.0.0
(https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithu
b.com%2Fllvm%2Fllvm-
project&data=04%7C01%7Chaiyangz%40microsoft.com%7Cb1a7f087851b48a29b
f308d94fe78490%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637628680585
035821%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBT
iI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=MKdTDUGKunqVOWEwafejDKuW0mpeN
aP1ssqiv4SBvzQ%3D&reserved=0
3f2c1e99e44d028d5e9dd685f3c568f2661f2f68)
reproduce (this is a W=1 build):
wget
https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fraw.gi
thubusercontent.com%2Fintel%2Flkp-
tests%2Fmaster%2Fsbin%2Fmake.cross&data=04%7C01%7Chaiyangz%40microso
ft.com%7Cb1a7f087851b48a29bf308d94fe78490%7C72f988bf86f141af91ab2d7cd011
db47%7C1%7C0%7C637628680585035821%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLj
AwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=gu
Hq8MagK88xMw%2F6ZxmhQExnmLoIlYLma4QR1gmUYdM%3D&reserved=0
-O ~/bin/make.cross
chmod +x ~/bin/make.cross
# install x86_64 cross compiling tool for clang build
# apt-get install binutils-x86-64-linux-gnu
#
https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.ke
rnel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Fcom
mit%2F%3Fid%3D7c9ff3deeee61b253715dcf968a6307af148c9b2&data=04%7C01%
7Chaiyangz%40microsoft.com%7Cb1a7f087851b48a29bf308d94fe78490%7C72f988bf
86f141af91ab2d7cd011db47%7C1%7C0%7C637628680585035821%7CUnknown%7CTWFpbG
Zsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D
%7C1000&sdata=N24YX%2FPLzONY5gKOu1U93%2B7uK4jm%2BIQYZzfA6z8FPHo%3D&a
mp;reserved=0
git remote add linus
https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.ke
rnel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git&d
ata=04%7C01%7Chaiyangz%40microsoft.com%7Cb1a7f087851b48a29bf308d94fe7849
0%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637628680585035821%7CUnkn
own%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLC
JXVCI6Mn0%3D%7C1000&sdata=6LkKnX%2BXhjmhh4m%2BzJ7y0JeQcwvwHw8NZP%2Bv
aXSdZV0%3D&reserved=0
git fetch --no-tags linus master
git checkout 7c9ff3deeee61b253715dcf968a6307af148c9b2
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross
clang-analyzer ARCH=x86_64 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 >>)
^~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/hid/hid-core.c:1601:3: note: Taking false branch
if (field->logical_minimum < 0) /* signed values */
^
drivers/hid/hid-core.c:1605:44: note: Passing value via 4th
parameter 'n'
implement(hid, data, offset + n * size, size,
^~~~
drivers/hid/hid-core.c:1605:4: note: Calling 'implement'
implement(hid, data, offset + n * size, size,

^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/hid/hid-core.c:1421:15: note: Assuming 'n' is <= 32
if (unlikely(n > 32)) {
^
include/linux/compiler.h:78:42: note: expanded from macro 'unlikely'
# define unlikely(x) __builtin_expect(!!(x), 0)
^
drivers/hid/hid-core.c:1421:2: note: Taking false branch
if (unlikely(n > 32)) {
^
drivers/hid/hid-core.c:1425:13: note: Assuming 'n' is >= 32
} else if (n < 32) {
^~~~~~
drivers/hid/hid-core.c:1425:9: note: Taking false branch
} else if (n < 32) {
^
drivers/hid/hid-core.c:1437:30: note: Passing the value 32 via 3rd
parameter 'n'
__implement(report, offset, n, value);
^
drivers/hid/hid-core.c:1437:2: note: Calling '__implement'
__implement(report, offset, n, value);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/hid/hid-core.c:1400:9: note: Assuming the condition is false
while (n - bits_to_set >= 0) {
^~~~~~~~~~~~~~~~~~~~
drivers/hid/hid-core.c:1400:2: note: Loop condition is false.
Execution continues on line 1411
while (n - bits_to_set >= 0) {
^
drivers/hid/hid-core.c:1411:6: note: 'n' is 32
if (n) {
^
drivers/hid/hid-core.c:1411:2: note: Taking true branch
if (n) {
^
drivers/hid/hid-core.c:1412:22: note: The result of the left shift
is undefined due to shifting by '32', which is greater or equal to the
width of type 'unsigned int'
u8 bit_mask = ((1U << n) - 1);
^ ~
drivers/hid/hid-core.c:1984:3: warning: Value stored to 'len' is
never read [clang-analyzer-deadcode.DeadStores]
len += sprintf(buf + len, "%shidraw%d", len ? "," :
"",
^
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/hid/hid-core.c:1984:3: note: Value stored to 'len' is never
read
len += sprintf(buf + len, "%shidraw%d", len ? "," :
"",
^
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Suppressed 5 warnings (5 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.
6 warnings generated.
Suppressed 6 warnings (6 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.
6 warnings generated.
Suppressed 6 warnings (6 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.
7 warnings generated.
Suppressed 7 warnings (7 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.
4 warnings generated.
Suppressed 4 warnings (4 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.
4 warnings generated.
Suppressed 4 warnings (4 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.
4 warnings generated.
Suppressed 4 warnings (4 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.
4 warnings generated.
Suppressed 4 warnings (4 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.
4 warnings generated.
Suppressed 4 warnings (4 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.
4 warnings generated.
Suppressed 4 warnings (4 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.
4 warnings generated.
Suppressed 4 warnings (4 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.
Suppressed 5 warnings (5 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.
4 warnings generated.
Suppressed 4 warnings (4 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.
9 warnings generated.
Suppressed 9 warnings (8 in non-user code, 1 with check filters).
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.
Suppressed 5 warnings (5 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.
6 warnings generated.

drivers/hv/channel_mgmt.c:785:22: warning: Assigned value is garbage
or undefined [clang-analyzer-core.uninitialized.Assign]

channel->target_cpu = target_cpu;
^

The for-loop before the assignment is always executed,
because ncpu = num_online_cpus() > 0:
for (i = 1; i <= ncpu + 1; i++) {

So the variable is assigned before Line 785:
target_cpu = cpumask_first(available_mask);

And, the following code ensures the available_mask is not empty:
if (cpumask_weight(alloced_mask) ==
cpumask_weight(cpumask_of_node(numa_node))) {
/*
* We have cycled through all the CPUs in the node;
* reset the alloced map.
*/
cpumask_clear(alloced_mask);
}

So the robot warning above can be ignored.

Thanks for the detailed explanation, please just ignore it.

Best Regards,
Rong Chen

Thanks,
- Haiyang

Next message: Greg Kroah-Hartman: "Linux 4.4.277"
Previous message: Cristian Marussi: "Re: [PATCH v6 07/17] firmware: arm_scmi: Handle concurrent and out-of-order messages"
In reply to: Haiyang Zhang: "RE: drivers/hv/channel_mgmt.c:785:22: warning: Assigned value is garbage or undefined [clang-analyzer-core.uninitialized.Assign]"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]