bridge.c:157:11: error: variable 'err' is used uninitialized whenever 'if' condition is false

[Please ignore if it is already reported]

Following build warnings/ errors noticed while building linux mainline
master branch
with clang-nightly, clang-13, clang-12, clang-11 and clang-10 for
arm64 architecture.
Whereas gcc-11 build pass.

# to reproduce this build locally: tuxmake --target-arch=arm64
--kconfig=defconfig --toolchain=clang-nightly --wrapper=none
--environment=KBUILD_BUILD_TIMESTAMP=@1630870764
--environment=KBUILD_BUILD_USER=tuxmake
--environment=KBUILD_BUILD_HOST=tuxmake --runtime=podman
--image=855116176053.dkr.ecr.us-east-1.amazonaws.com/tuxmake/arm64_clang-nightly
config default kernel xipkernel modules dtbs dtbs-legacy debugkernel
headers
make --silent --keep-going --jobs=8
O=/home/tuxbuild/.cache/tuxmake/builds/current ARCH=arm64
CROSS_COMPILE=aarch64-linux-gnu- HOSTCC=clang CC=clang defconfig
make --silent --keep-going --jobs=8
O=/home/tuxbuild/.cache/tuxmake/builds/current ARCH=arm64
CROSS_COMPILE=aarch64-linux-gnu- HOSTCC=clang CC=clang
scripts/dtc/include-prefixes/arm/bcm2711-rpi-4-b.dts:220.10-231.4:
Warning (pci_device_reg): /scb/pcie@7d500000/pci@1,0: PCI unit address
format error, expected 0,0
scripts/dtc/include-prefixes/arm/bcm2711-rpi-4-b.dts:220.10-231.4:
Warning (pci_device_reg): /scb/pcie@7d500000/pci@1,0: PCI unit address
format error, expected 0,0
arch/arm64/boot/dts/rockchip/rk3399-gru.dtsi:464.3-52: Warning
(pci_device_reg): /pcie@f8000000/pcie@0,0:reg: PCI reg address is not
configuration space
arch/arm64/boot/dts/rockchip/rk3399-gru.dtsi:464.3-52: Warning
(pci_device_reg): /pcie@f8000000/pcie@0,0:reg: PCI reg address is not
configuration space
arch/arm64/boot/dts/rockchip/rk3399-gru.dtsi:464.3-52: Warning
(pci_device_reg): /pcie@f8000000/pcie@0,0:reg: PCI reg address is not
configuration space
arch/arm64/boot/dts/rockchip/rk3399-gru.dtsi:464.3-52: Warning
(pci_device_reg): /pcie@f8000000/pcie@0,0:reg: PCI reg address is not
configuration space
arch/arm64/kvm/hyp/nvhe/Makefile:58: FORCE prerequisite is missing
drivers/net/ethernet/mellanox/mlx5/core/en/rep/bridge.c:157:11: error:
variable 'err' is used uninitialized whenever 'if' condition is false
[-Werror,-Wsometimes-uninitialized]
        else if (mlx5_esw_bridge_dev_same_hw(rep, esw))
                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/mellanox/mlx5/core/en/rep/bridge.c:164:9: note:
uninitialized use occurs here
        return err;
               ^~~
drivers/net/ethernet/mellanox/mlx5/core/en/rep/bridge.c:157:7: note:
remove the 'if' if its condition is always true
        else if (mlx5_esw_bridge_dev_same_hw(rep, esw))
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/mellanox/mlx5/core/en/rep/bridge.c:140:9: note:
initialize the variable 'err' to silence this warning
        int err;
               ^
                = 0
drivers/net/ethernet/mellanox/mlx5/core/en/rep/bridge.c:262:7: error:
variable 'err' is used uninitialized whenever switch case is taken
[-Werror,-Wsometimes-uninitialized]
        case SWITCHDEV_ATTR_ID_PORT_BRIDGE_FLAGS:
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/mellanox/mlx5/core/en/rep/bridge.c:276:9: note:
uninitialized use occurs here
        return err;
               ^~~
drivers/net/ethernet/mellanox/mlx5/core/en/rep/bridge.c:257:7: error:
variable 'err' is used uninitialized whenever 'if' condition is false
[-Werror,-Wsometimes-uninitialized]
                if (attr->u.brport_flags.mask & ~(BR_LEARNING |
BR_FLOOD | BR_MCAST_FLOOD)) {

^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/mellanox/mlx5/core/en/rep/bridge.c:276:9: note:
uninitialized use occurs here
        return err;
               ^~~
drivers/net/ethernet/mellanox/mlx5/core/en/rep/bridge.c:257:3: note:
remove the 'if' if its condition is always true
                if (attr->u.brport_flags.mask & ~(BR_LEARNING |
BR_FLOOD | BR_MCAST_FLOOD)) {

^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/mellanox/mlx5/core/en/rep/bridge.c:247:9: note:
initialize the variable 'err' to silence this warning
        int err;
               ^
                = 0
3 errors generated.
make[6]: *** [scripts/Makefile.build:277:
drivers/net/ethernet/mellanox/mlx5/core/en/rep/bridge.o] Error 1
make[6]: Target '__build' not remade because of errors.
make[5]: *** [scripts/Makefile.build:540:
drivers/net/ethernet/mellanox/mlx5/core] Error 2
make[5]: Target '__build' not remade because of errors.
make[4]: *** [scripts/Makefile.build:540: drivers/net/ethernet/mellanox] Error 2
make[4]: Target '__build' not remade because of errors.
make[3]: *** [scripts/Makefile.build:540: drivers/net/ethernet] Error 2
make[3]: Target '__build' not remade because of errors.
make[2]: *** [scripts/Makefile.build:540: drivers/net] Error 2
make[2]: Target '__build' not remade because of errors.
make[1]: *** [Makefile:1872: drivers] Error 2
make[1]: Target '__all' not remade because of errors.
make: *** [Makefile:219: __sub-make] Error 2
make: Target '__all' not remade because of errors.

Build config:
https://builds.tuxbuild.com/1xjZrnXEZfc3qYzziclNRaugAaN/config

Reported-by: Linux Kernel Functional Testing <redacted>

meta data:
-----------
    git_describe: v5.14-9687-g27151f177827
    git_repo: https://gitlab.com/Linaro/lkft/mirrors/torvalds/linux-mainline
    git_sha: 27151f177827d478508e756c7657273261aaf8a9
    git_short_log: 27151f177827 (\Merge tag
'perf-tools-for-v5.15-2021-09-04' of
git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux\)
    kconfig: [
        defconfig
    ],
    kernel_version: 5.14.0
    status_message: failure while building tuxmake target(s): default
    target_arch: arm64
    toolchain: clang-nightly, clang-13, clang-12, clang-11 and clang-10

steps to reproduce:
https://builds.tuxbuild.com/1xjZrnXEZfc3qYzziclNRaugAaN/tuxmake_reproducer.sh

--
Linaro LKFT
https://lkft.linaro.org

On Mon, Sep 6, 2021 at 2:11 AM Naresh Kamboju [off-list ref] wrote:

drivers/net/ethernet/mellanox/mlx5/core/en/rep/bridge.c:157:11: error:
variable 'err' is used uninitialized whenever 'if' condition is false

That compiler warning (now error) seems to be entirely valid.

That's a

    if (..)
    else if (..)

and if neither are valid then the code will return an uninitialized 'err'.

It's possible the two conditionals are guaranteed to cover all cases,
but as the compiler says, in that case the "if" in the else clause is
pointless and should be removed.

But it does look like 'ret' should probably just be initialized to 0.

              Linus

On Mon 06 Sep 2021 at 19:39, Linus Torvalds [off-list ref] wrote:

On Mon, Sep 6, 2021 at 2:11 AM Naresh Kamboju [off-list ref] wrote:

quoted

drivers/net/ethernet/mellanox/mlx5/core/en/rep/bridge.c:157:11: error:
variable 'err' is used uninitialized whenever 'if' condition is false

That compiler warning (now error) seems to be entirely valid.

I agree, this is a real issue. It had been reported before and my fix
for it was submitted by Saeed last week but wasn't accepted since it was
part of larger series that also included features and net-next had
already been closed by that time. As far as I understand it is pending
submission to net as part of series of bug fixes. Sorry for the delay.

That's a

    if (..)
    else if (..)

and if neither are valid then the code will return an uninitialized 'err'.

It's possible the two conditionals are guaranteed to cover all cases,
but as the compiler says, in that case the "if" in the else clause is
pointless and should be removed.

But it does look like 'ret' should probably just be initialized to 0.

Yep, this if exactly what I did in my patch "net/mlx5: Bridge, fix
uninitialized variable usage".

              Linus

On Mon, 2021-09-06 at 20:35 +0300, Vlad Buslov wrote:

On Mon 06 Sep 2021 at 19:39, Linus Torvalds
[off-list ref] wrote:

quoted

On Mon, Sep 6, 2021 at 2:11 AM Naresh Kamboju
[off-list ref] wrote:

quoted

drivers/net/ethernet/mellanox/mlx5/core/en/rep/bridge.c:157:11:
error:
variable 'err' is used uninitialized whenever 'if' condition is
false

That compiler warning (now error) seems to be entirely valid.

I agree, this is a real issue. It had been reported before and my fix
for it was submitted by Saeed last week but wasn't accepted since it
was
part of larger series that also included features and net-next had
already been closed by that time. As far as I understand it is
pending
submission to net as part of series of bug fixes. Sorry for the
delay.

yes, the fix will be submitted shortly to net/rc branch.
due to bad net-next timing the patch couldn't make it to -next.