Greeting,

FYI, we noticed UBSAN:array-index-out-of-bounds_in_fs/namespace.c due to commit (built with gcc-11):

commit: 0fc58d2df77109ff6f18a334b1479e7b5fd9449e ("vfs: prepare for mount write barrier")
https://github.com/amir73il/linux mnt_write_barrier

in testcase: boot

on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G

caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):


If you fix the issue, kindly add following tag
| Reported-by: kernel test robot <oliver.sang@intel.com>
| Link: https://lore.kernel.org/oe-lkp/202211240919.3dafb6ca-oliver.sang@intel.com


[    0.690640][    T0] UBSAN: array-index-out-of-bounds in fs/namespace.c:223:19
[    0.691494][    T0] index 2 is out of range for type 'int [2]'
[    0.692135][    T0] CPU: 0 PID: 0 Comm: swapper Not tainted 6.1.0-rc4-00019-g0fc58d2df771 #1
[    0.693059][    T0] Call Trace:
[ 0.693417][ T0] dump_stack_lvl (??:?) 
[ 0.693924][ T0] dump_stack (??:?) 
[ 0.694383][ T0] ubsan_epilogue (ubsan.c:?) 
[ 0.694919][ T0] __ubsan_handle_out_of_bounds (??:?) 
[ 0.695487][ T0] ? kstrdup (??:?) 
[ 0.695487][ T0] alloc_vfsmnt (namespace.c:?) 
[ 0.695487][ T0] vfs_create_mount (??:?) 
[ 0.695487][ T0] vfs_kern_mount (??:?) 
[ 0.695487][ T0] ? shmem_parse_one (shmem.c:?) 
[ 0.695487][ T0] kern_mount (??:?) 
[ 0.695487][ T0] shmem_init (??:?) 
[ 0.695487][ T0] mnt_init (??:?) 
[ 0.695487][ T0] ? files_init (??:?) 
[ 0.695487][ T0] vfs_caches_init (??:?) 
[ 0.695487][ T0] start_kernel (??:?) 
[ 0.695487][ T0] i386_start_kernel (??:?) 
[ 0.695487][ T0] startup_32_smp (??:?) 
[    0.695491][    T0] ================================================================================
[    0.699894][    T0] Last level iTLB entries: 4KB 0, 2MB 0, 4MB 0
[    0.700578][    T0] Last level dTLB entries: 4KB 0, 2MB 0, 4MB 0, 1GB 0
[    0.701319][    T0] CPU: Intel Xeon E312xx (Sandy Bridge) (family: 0x6, model: 0x2a, stepping: 0x1)


To reproduce:

        # build kernel
	cd linux
	cp config-6.1.0-rc4-00019-g0fc58d2df771 .config
	make HOSTCC=gcc-11 CC=gcc-11 ARCH=i386 olddefconfig prepare modules_prepare bzImage modules
	make HOSTCC=gcc-11 CC=gcc-11 ARCH=i386 INSTALL_MOD_PATH=<mod-install-dir> modules_install
	cd <mod-install-dir>
	find lib/ | cpio -o -H newc --quiet | gzip > modules.cgz


        git clone https://github.com/intel/lkp-tests.git
        cd lkp-tests
        bin/lkp qemu -k <bzImage> -m modules.cgz job-script # job-script is attached in this email

        # if come across any failure that blocks the test,
        # please remove ~/.lkp and /lkp dir to run from a clean state.



-- 
0-DAY CI Kernel Test Service
https://01.org/lkp