On 11/24/20 12:03 AM, Joseph Qi wrote: > Abaci Fuzz reported a shift-out-of-bounds BUG in io_uring_create(): > > [ 59.598207] UBSAN: shift-out-of-bounds in ./include/linux/log2.h:57:13 > [ 59.599665] shift exponent 64 is too large for 64-bit type 'long unsigned int' > [ 59.601230] CPU: 0 PID: 963 Comm: a.out Not tainted 5.10.0-rc4+ #3 > [ 59.602502] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 > [ 59.603673] Call Trace: > [ 59.604286] dump_stack+0x107/0x163 > [ 59.605237] ubsan_epilogue+0xb/0x5a > [ 59.606094] __ubsan_handle_shift_out_of_bounds.cold+0xb2/0x20e > [ 59.607335] ? lock_downgrade+0x6c0/0x6c0 > [ 59.608182] ? rcu_read_lock_sched_held+0xaf/0xe0 > [ 59.609166] io_uring_create.cold+0x99/0x149 > [ 59.610114] io_uring_setup+0xd6/0x140 > [ 59.610975] ? io_uring_create+0x2510/0x2510 > [ 59.611945] ? lockdep_hardirqs_on_prepare+0x286/0x400 > [ 59.613007] ? syscall_enter_from_user_mode+0x27/0x80 > [ 59.614038] ? trace_hardirqs_on+0x5b/0x180 > [ 59.615056] do_syscall_64+0x2d/0x40 > [ 59.615940] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > [ 59.617007] RIP: 0033:0x7f2bb8a0b239 > > This is caused by roundup_pow_of_two() if the input entries larger > enough, e.g. 2^32-1. For sq_entries, it will check first and we allow > at most IORING_MAX_ENTRIES, so it is okay. But for cq_entries, we do > round up first, that may overflow and truncate it to 0, which is not > the expected behavior. So check the cq size first and then do round up. Applied, thanks. -- Jens Axboe
