From: Xiaoguang Wang xiaoguang.wang@linux.alibaba.com
Abaci Fuzz reported a double-free or invalid-free BUG in io_commit_cqring(): [ 95.504842] BUG: KASAN: double-free or invalid-free in io_commit_cqring+0x3ec/0x8e0 [ 95.505921] [ 95.506225] CPU: 0 PID: 4037 Comm: io_wqe_worker-0 Tainted: G B W 5.10.0-rc5+ #1 [ 95.507434] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 [ 95.508248] Call Trace: [ 95.508683] dump_stack+0x107/0x163 [ 95.509323] ? io_commit_cqring+0x3ec/0x8e0 [ 95.509982] print_address_description.constprop.0+0x3e/0x60 [ 95.510814] ? vprintk_func+0x98/0x140 [ 95.511399] ? io_commit_cqring+0x3ec/0x8e0 [ 95.512036] ? io_commit_cqring+0x3ec/0x8e0 [ 95.512733] kasan_report_invalid_free+0x51/0x80 [ 95.513431] ? io_commit_cqring+0x3ec/0x8e0 [ 95.514047] __kasan_slab_free+0x141/0x160 [ 95.514699] kfree+0xd1/0x390 [ 95.515182] io_commit_cqring+0x3ec/0x8e0 [ 95.515799] __io_req_complete.part.0+0x64/0x90 [ 95.516483] io_wq_submit_work+0x1fa/0x260 [ 95.517117] io_worker_handle_work+0xeac/0x1c00 [ 95.517828] io_wqe_worker+0xc94/0x11a0 [ 95.518438] ? io_worker_handle_work+0x1c00/0x1c00 [ 95.519151] ? __kthread_parkme+0x11d/0x1d0 [ 95.519806] ? io_worker_handle_work+0x1c00/0x1c00 [ 95.520512] ? io_worker_handle_work+0x1c00/0x1c00 [ 95.521211] kthread+0x396/0x470 [ 95.521727] ? _raw_spin_unlock_irq+0x24/0x30 [ 95.522380] ? kthread_mod_delayed_work+0x180/0x180 [ 95.523108] ret_from_fork+0x22/0x30 [ 95.523684] [ 95.523985] Allocated by task 4035: [ 95.524543] kasan_save_stack+0x1b/0x40 [ 95.525136] __kasan_kmalloc.constprop.0+0xc2/0xd0 [ 95.525882] kmem_cache_alloc_trace+0x17b/0x310 [ 95.533930] io_queue_sqe+0x225/0xcb0 [ 95.534505] io_submit_sqes+0x1768/0x25f0 [ 95.535164] __x64_sys_io_uring_enter+0x89e/0xd10 [ 95.535900] do_syscall_64+0x33/0x40 [ 95.536465] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 95.537199] [ 95.537505] Freed by task 4035: [ 95.538003] kasan_save_stack+0x1b/0x40 [ 95.538599] kasan_set_track+0x1c/0x30 [ 95.539177] kasan_set_free_info+0x1b/0x30 [ 95.539798] __kasan_slab_free+0x112/0x160 [ 95.540427] kfree+0xd1/0x390 [ 95.540910] io_commit_cqring+0x3ec/0x8e0 [ 95.541516] io_iopoll_complete+0x914/0x1390 [ 95.542150] io_do_iopoll+0x580/0x700 [ 95.542724] io_iopoll_try_reap_events.part.0+0x108/0x200 [ 95.543512] io_ring_ctx_wait_and_kill+0x118/0x340 [ 95.544206] io_uring_release+0x43/0x50 [ 95.544791] __fput+0x28d/0x940 [ 95.545291] task_work_run+0xea/0x1b0 [ 95.545873] do_exit+0xb6a/0x2c60 [ 95.546400] do_group_exit+0x12a/0x320 [ 95.546967] __x64_sys_exit_group+0x3f/0x50 [ 95.547605] do_syscall_64+0x33/0x40 [ 95.548155] entry_SYSCALL_64_after_hwframe+0x44/0xa9
The reason is that once we got a non EAGAIN error in io_wq_submit_work(), we'll complete req by calling io_req_complete(), which will hold completion_lock to call io_commit_cqring(), but for polled io, io_iopoll_complete() won't hold completion_lock to call io_commit_cqring(), then there maybe concurrent access to ctx->defer_list, double free may happen.
To fix this bug, we always let io_iopoll_complete() complete polled io.
Cc: stable@vger.kernel.org # 5.5+ Reported-by: Abaci Fuzz abaci@linux.alibaba.com Signed-off-by: Xiaoguang Wang xiaoguang.wang@linux.alibaba.com Reviewed-by: Pavel Begunkov asml.silence@gmail.com Reviewed-by: Joseph Qi joseph.qi@linux.alibaba.com Signed-off-by: Pavel Begunkov asml.silence@gmail.com --- fs/io_uring.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c index a2a7c65a77aa..c895a306f919 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -6074,8 +6074,19 @@ static struct io_wq_work *io_wq_submit_work(struct io_wq_work *work) }
if (ret) { - req_set_fail_links(req); - io_req_complete(req, ret); + /* + * io_iopoll_complete() does not hold completion_lock to complete + * polled io, so here for polled io, just mark it done and still let + * io_iopoll_complete() complete it. + */ + if (req->ctx->flags & IORING_SETUP_IOPOLL) { + struct kiocb *kiocb = &req->rw.kiocb; + + kiocb_done(kiocb, ret, NULL); + } else { + req_set_fail_links(req); + io_req_complete(req, ret); + } }
return io_steal_work(req);