On Fri, Jun 5, 2020 at 1:10 AM kernel test robot <rong.a.c...@intel.com> wrote: > > Greeting, > > FYI, we noticed the following commit (built with gcc-4.9): > > commit: a6211caa634da39d861a47437ffcda8b38ef421b ("net: revert "net: get rid > of an signed integer overflow in ip_idents_reserve()"") > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master > > in testcase: boot > > on test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 8G > > 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 <rong.a.c...@intel.com> >
There you go. We decided this was a bogus report, and that UBSAN requires sane compilers. Please read the fine comment that was added in this commit and update your compiler or do not mess with compiler flags. + /* If UBSAN reports an error there, please make sure your compiler + * supports -fno-strict-overflow before reporting it that was a bug + * in UBSAN, and it has been fixed in GCC-8. + */ + return atomic_add_return(segs + delta, p_id) - segs; Thanks. > > [ 35.019158] > ================================================================================ > [ 35.019995] UBSAN: signed-integer-overflow in > arch/x86/include/asm/atomic.h:167:2 > [ 35.020884] -1045826149 + -1341282523 cannot be represented in type 'int' > [ 35.021544] CPU: 0 PID: 350 Comm: systemd-timesyn Tainted: G S > 5.7.0-rc5-00221-ga6211caa634da #1 > [ 35.022550] Call Trace: > [ 35.022812] dump_stack+0x16/0x26 > [ 35.023151] ubsan_epilogue+0x8/0x40 > [ 35.023526] handle_overflow+0x80/0xa0 > [ 35.023925] ? __ip_append_data+0x8ca/0xdd0 > [ 35.024408] __ubsan_handle_add_overflow+0xa/0x10 > [ 35.024872] ip_idents_reserve+0x79/0x90 > [ 35.025263] __ip_select_ident+0x48/0x70 > [ 35.025659] __ip_make_skb+0x32f/0x410 > [ 35.026039] ip_make_skb+0xa6/0xe0 > [ 35.026383] ? ip_reply_glue_bits+0x50/0x50 > [ 35.026770] ? ip_route_output_key_hash+0xb6/0xe0 > [ 35.027221] udp_sendmsg+0x577/0xba0 > [ 35.027551] ? ip_reply_glue_bits+0x50/0x50 > [ 35.027960] ? lock_release+0x9d/0x260 > [ 35.028328] inet_sendmsg+0x2e/0x50 > [ 35.028819] __sys_sendto+0xe2/0x130 > [ 35.029178] ? lock_acquire+0x92/0x310 > [ 35.029552] ? __might_fault+0x41/0x80 > [ 35.029903] ? find_held_lock+0x2d/0xd0 > [ 35.030262] ? lock_release+0x9d/0x260 > [ 35.030620] __ia32_sys_socketcall+0x141/0x240 > [ 35.031064] do_int80_syscall_32+0x46/0x3d0 > [ 35.031470] entry_INT80_32+0x113/0x113 > [ 35.031854] EIP: 0xb7f54a02 > [ 35.032133] Code: 95 01 00 05 25 36 02 00 83 ec 14 8d 80 e8 99 ff ff 50 6a > 02 e8 1f ff 00 00 c7 04 24 7f 00 00 00 e8 7e 87 01 00 66 90 90 cd 80 <c3> 8d > b6 00 00 00 00 8d bc 27 00 00 00 00 8b 1c 24 c3 8d b6 00 00 > [ 35.033938] EAX: ffffffda EBX: 0000000b ECX: bfecd7c8 EDX: 00000000 > [ 35.034562] ESI: b7cd3000 EDI: 00000000 EBP: 00000000 ESP: bfecd7bc > [ 35.035199] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b EFLAGS: 00000293 > [ 35.035865] > ================================================================================ > [ OK ] Started OpenBSD Secure Shell server. > [ OK ] Started LSB: Start and stop bmc-watchdog. > [ OK ] Started LSB: Execute the kexec -e command to reboot system. > [ OK ] Started Login Service. > Starting Preprocess NFS configuration... > [ OK ] Reached target Host and Network Name Lookups. > Starting LSB: Load kernel image with kexec... > [ OK ] Reached target Login Prompts. > [ OK ] Started Preprocess NFS configuration. > Starting Notify NFS peers of a restart... > Starting NFS status monitor for NFSv2/3 locking.... > [ OK ] Started Notify NFS peers of a restart. > [ OK ] Started LSB: Load kernel image with kexec. > [ OK ] Started NFS status monitor for NFSv2/3 locking.. > [ 48.881188] sysrq: Emergency Sync > [ 48.881750] sysrq: Resetting > > > To reproduce: > > # build kernel > cd linux > cp config-5.7.0-rc5-00221-ga6211caa634da .config > make HOSTCC=gcc-4.9 CC=gcc-4.9 ARCH=i386 olddefconfig prepare > modules_prepare bzImage > > git clone https://github.com/intel/lkp-tests.git > cd lkp-tests > bin/lkp qemu -k <bzImage> job-script # job-script is attached in this > email > > > > Thanks, > Rong Chen >