On Tue, 2016-09-20 at 14:00 +0200, Jiri Pirko wrote: > Hi. > > I'm consistently getting following UBSAN warning on every bootup: > > [ 47.545820] > ================================================================================ > [ 47.554340] UBSAN: Undefined behaviour in > ./arch/x86/include/asm/atomic.h:156:11 > [ 47.561808] signed integer overflow: > [ 47.565420] -2117905507 + -695755206 cannot be represented in type 'int' > [ 47.572226] CPU: 0 PID: 389 Comm: ntpd Not tainted 4.8.0-rc6jiri+ #1 > [ 47.578636] Hardware name: Mellanox Technologies Ltd. Mellanox > switch/Mellanox switch, BIOS 4.6.5 05/21/2015 > [ 47.588586] ffffffff847bf8c0 00000000987b8f47 ffff8803829af5a8 > ffffffff818354e3 > [ 47.596165] 0000000041b58ab3 ffffffff8277e711 ffffffff81835431 > ffff8803829af5d0 > [ 47.603722] ffff8803829af580 ffffffffd6879e3a 1ffffffff08f8214 > ffffed0070535e6c > [ 47.611298] Call Trace: > [ 47.613795] [<ffffffff818354e3>] dump_stack+0xb2/0x10f > [ 47.619077] [<ffffffff81835431>] ? _atomic_dec_and_lock+0xa1/0xa1 > [ 47.625327] [<ffffffff818a884f>] ubsan_epilogue+0xd/0x4e > [ 47.630811] [<ffffffff818a9821>] handle_overflow+0x190/0x1de > [ 47.636627] [<ffffffff818a9691>] ? > __ubsan_handle_negate_overflow+0x140/0x140 > [ 47.643914] [<ffffffff81863130>] ? > iov_iter_copy_from_user_atomic+0x6e0/0x6e0 > [ 47.651219] [<ffffffff811e6f79>] ? __lock_acquire.isra.17+0xb79/0xe50 > [ 47.657832] [<ffffffff81e581f2>] ? ip_generic_getfrag+0xd2/0x190 > [ 47.664011] [<ffffffff81e58120>] ? ip_setup_cork+0x320/0x320 > [ 47.669827] [<ffffffff818a987d>] __ubsan_handle_add_overflow+0xe/0x10 > [ 47.676444] [<ffffffff81e41d52>] ip_idents_reserve+0xb2/0xe0 > [ 47.682254] [<ffffffff81e443e9>] __ip_select_ident+0x159/0x1b0 > [ 47.688248] [<ffffffff81e44290>] ? update_or_create_fnhe+0x850/0x850 > [ 47.694782] [<ffffffff81e58120>] ? ip_setup_cork+0x320/0x320 > [ 47.700624] [<ffffffff81e5ef40>] __ip_make_skb+0x8a0/0xab0 > [ 47.706259] [<ffffffff81e5f3fd>] ip_make_skb+0x17d/0x1d0 > [ 47.711717] [<ffffffff81e58120>] ? ip_setup_cork+0x320/0x320 > [ 47.717526] [<ffffffff81e5f280>] ? ip_flush_pending_frames+0x20/0x20 > [ 47.724032] [<ffffffff81e46ef0>] ? ip_rt_update_pmtu+0x4f0/0x4f0 > [ 47.730231] [<ffffffff81f35291>] ? xfrm_lookup_route+0x21/0xe0 > [ 47.736216] [<ffffffff81ec0cdb>] udp_sendmsg+0x9db/0xf60 > [ 47.741668] [<ffffffff81e58120>] ? ip_setup_cork+0x320/0x320 > [ 47.747472] [<ffffffff81ec0300>] ? udp_abort+0x70/0x70 > [ 47.752763] [<ffffffff81ede3d8>] inet_sendmsg+0x198/0x220 > [ 47.758324] [<ffffffff81ede292>] ? inet_sendmsg+0x52/0x220 > [ 47.763982] [<ffffffff81ede240>] ? inet_recvmsg+0x300/0x300 > [ 47.769728] [<ffffffff81d6fd25>] sock_sendmsg+0xa5/0xd0 > [ 47.775100] [<ffffffff81d72f70>] SYSC_sendto+0x1d0/0x280 > [ 47.780551] [<ffffffff81d72da0>] ? SYSC_connect+0x200/0x200 > [ 47.786283] [<ffffffff814f66df>] ? poll_select_copy_remaining+0x2af/0x310 > [ 47.793265] [<ffffffff814f6430>] ? set_fd_set+0x60/0x60 > [ 47.798665] [<ffffffff811ee360>] ? do_raw_spin_trylock+0x90/0x90 > [ 47.804853] [<ffffffff814f80e3>] ? SyS_select+0x1a3/0x200 > [ 47.810399] [<ffffffff814f7f40>] ? core_sys_select+0x570/0x570 > [ 47.816415] [<ffffffff8100467c>] ? exit_to_usermode_loop+0xec/0x110 > [ 47.822842] [<ffffffff811e8abd>] ? lockdep_sys_exit+0x2d/0xb0 > [ 47.828769] [<ffffffff81004016>] ? lockdep_sys_exit_thunk+0x16/0x30 > [ 47.835199] [<ffffffff81d7433e>] SyS_sendto+0xe/0x10 > [ 47.840321] [<ffffffff820381f2>] entry_SYSCALL_64_fastpath+0x1a/0xa9 > [ 47.846826] > ================================================================================ > > Looks like this might be result of following commit: > > commit 04ca6973f7c1a0d8537f2d9906a0cf8e69886d75 > Author: Eric Dumazet <eduma...@google.com> > Date: Sat Jul 26 08:58:10 2014 +0200 > > ip: make IP identifiers less predictable > > Eric, could you please take look at that?
Sure I do not think we have to worry here. These is best effort, and unfortunately atomic_t are int. Adding uatomic_t helpers in the kernel with unsigned int would be a huge effort, given this would touch all arches.
