Re: test_vsyscall.c:500:22: warning: '__builtin_memcmp_eq' specified bound 4096 exceeds source size 0

[Greg Kroah-Hartman]

On Thu, Jan 06, 2022 at 02:55:53PM +0530, Naresh Kamboju wrote:
> While building selftests the following warnings were noticed for x86_64
> architecture on Linux stable v5.15.13 kernel.
> 
> metadata:
>   git repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
>   git commit: 734eb1fd2073f503f5c6b44f1c0d453ca6986b84
>   git describe: v5.15.13
>   toolchain":  gcc-11
>   kernel-config: https://builds.tuxbuild.com/23HFo8abXIL6i4FFfSYiJlqAYMW/config
> 
> x86_64-linux-gnu-gcc -m64 -o \
> /home/tuxbuild/.cache/tuxmake/builds/current/kselftest/x86/test_vsyscall_64 \
>  -O2 -g -std=gnu99 -pthread -Wall -no-pie \
>  -DCAN_BUILD_64 test_vsyscall.c helpers.h -lrt -ldl
> 
> test_vsyscall.c: In function 'test_process_vm_readv':
> test_vsyscall.c:500:22: warning: '__builtin_memcmp_eq' specified bound
> 4096 exceeds source size 0 [-Wstringop-overread]
>   500 |                 if (!memcmp(buf, (const void
> *)0xffffffffff600000, 4096)) {
>       |                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Reported-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx>
> 
> Build link:
> https://builds.tuxbuild.com/23HFo8abXIL6i4FFfSYiJlqAYMW/
> 
> # To install tuxmake on your system globally:
> # sudo pip3 install -U tuxmake
> 
> tuxmake --runtime podman --target-arch x86_64 --toolchain gcc-11 \
>  --kconfig https://builds.tuxbuild.com/23HFo8abXIL6i4FFfSYiJlqAYMW/config \
>  cpupower headers kernel kselftest kselftest-merge modules

Is this a new regression from 5.15.0?  Is it also present on Linus's tree?

thanks,

greg k-h