On Thu, Aug 08, 2019 at 02:39:42PM +0200, David Sterba wrote: > The following warning pops up with enabled UBSAN in tests fstests/generic/303: > > [23127.529395] UBSAN: Undefined behaviour in fs/read_write.c:1725:7 > [23127.529400] signed integer overflow: > [23127.529403] 4611686018427322368 + 9223372036854775807 cannot be represented in type 'long long int' > [23127.529412] CPU: 4 PID: 26180 Comm: xfs_io Not tainted 5.2.0-rc2-1.ge195904-vanilla+ #450 > [23127.556999] Hardware name: empty empty/S3993, BIOS PAQEX0-3 02/24/2008 > [23127.557001] Call Trace: > [23127.557060] dump_stack+0x67/0x9b > [23127.557070] ubsan_epilogue+0x9/0x40 > [23127.573496] handle_overflow+0xb3/0xc0 > [23127.573514] do_clone_file_range+0x28f/0x2a0 > [23127.573547] vfs_clone_file_range+0x35/0xb0 > [23127.573564] ioctl_file_clone+0x8d/0xc0 > [23127.590144] do_vfs_ioctl+0x300/0x700 > [23127.590160] ksys_ioctl+0x70/0x80 > [23127.590203] ? trace_hardirqs_off_thunk+0x1a/0x1c > [23127.590210] __x64_sys_ioctl+0x16/0x20 > [23127.590215] do_syscall_64+0x5c/0x1d0 > [23127.590224] entry_SYSCALL_64_after_hwframe+0x49/0xbe > [23127.590231] RIP: 0033:0x7ff6d7250327 > [23127.590241] RSP: 002b:00007ffe3a38f1d8 EFLAGS: 00000206 ORIG_RAX: 0000000000000010 > [23127.590246] RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007ff6d7250327 > [23127.590249] RDX: 00007ffe3a38f220 RSI: 000000004020940d RDI: 0000000000000003 > [23127.590252] RBP: 0000000000000000 R08: 00007ffe3a3c80a0 R09: 00007ffe3a3c8080 > [23127.590255] R10: 000000000fa99fa0 R11: 0000000000000206 R12: 0000000000000000 > [23127.590260] R13: 0000000000000000 R14: 3fffffffffff0000 R15: 00007ff6d750a20c > > As loff_t is a signed type, we should use the safe overflow checks > instead of relying on compiler implementation. > > The bogus values are intentional and the test is supposed to verify the > boundary conditions. > > Signed-off-by: David Sterba <dsterba@xxxxxxxx> Reviewed-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
