From: Joseph Qi joseph.qi@linux.alibaba.com
[ Upstream commit eb2667b343361863da7b79be26de641e22844ba0 ]
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.
Fixes: 88ec3211e463 ("io_uring: round-up cq size before comparing with rounded sq size") Reported-by: Abaci Fuzz abaci@linux.alibaba.com Signed-off-by: Joseph Qi joseph.qi@linux.alibaba.com Reviewed-by: Stefano Garzarella sgarzare@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- fs/io_uring.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c index 5d9f8e40b93d3..6d729a278535e 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -8907,14 +8907,16 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p, * to a power-of-two, if it isn't already. We do NOT impose * any cq vs sq ring sizing. */ - p->cq_entries = roundup_pow_of_two(p->cq_entries); - if (p->cq_entries < p->sq_entries) + if (!p->cq_entries) return -EINVAL; if (p->cq_entries > IORING_MAX_CQ_ENTRIES) { if (!(p->flags & IORING_SETUP_CLAMP)) return -EINVAL; p->cq_entries = IORING_MAX_CQ_ENTRIES; } + p->cq_entries = roundup_pow_of_two(p->cq_entries); + if (p->cq_entries < p->sq_entries) + return -EINVAL; } else { p->cq_entries = 2 * p->sq_entries; }