On Thu, 30 Sept 2021 at 05:12, yangerkun <yangerkun@xxxxxxxxxx> wrote: > > Our testcase trigger follow UAF: > > [ 153.939147] ================================================================== > [ 153.942199] BUG: KASAN: use-after-free in ext4_dio_read_iter+0xcc/0x1a0 > [ 153.943331] Read of size 8 at addr ffff88803b7f1500 by task fsstress/726 > [ 153.948182] Call Trace: > [ 153.948628] ? dump_stack_lvl+0x73/0x9f > [ 153.950255] ? ext4_dio_read_iter+0xcc/0x1a0 > [ 153.950972] ? ext4_dio_read_iter+0xcc/0x1a0 > [ 153.951693] ? kasan_report.cold+0x81/0x165 > [ 153.952429] ? ext4_dio_read_iter+0xcc/0x1a0 > [ 153.953190] ? __asan_load8+0x74/0x110 > [ 153.953856] ? ext4_dio_read_iter+0xcc/0x1a0 > [ 153.954612] ? ext4_file_read_iter+0x1df/0x2a0 > [ 153.955394] ? ext4_dio_read_iter+0x1a0/0x1a0 > [ 153.956159] ? vfs_iocb_iter_read+0xd5/0x330 > [ 153.956916] ? ovl_read_iter+0x15f/0x270 > [ 153.957605] ? ovl_aio_cleanup_handler+0x2a0/0x2a0 > [ 153.958436] ? aio_setup_rw+0xbf/0xe0 > [ 153.959101] ? aio_read+0x190/0x2d0 > [ 153.959750] ? aio_write+0x3e0/0x3e0 > [ 153.960404] ? __kasan_check_read+0x1d/0x30 > [ 153.961167] ? ext4_file_getattr+0x116/0x1b0 > [ 153.961978] ? __put_user_ns+0x40/0x40 > [ 153.962714] ? kasan_poison+0x40/0x90 > [ 153.963384] ? set_alloc_info+0x46/0x70 > [ 153.964102] ? __kasan_check_write+0x20/0x30 > [ 153.964856] ? __fget_files+0x106/0x180 > [ 153.965571] ? io_submit_one+0xaa7/0x1480 > [ 153.966325] ? aio_poll_complete_work+0x590/0x590 > [ 153.967713] ? ioctl_file_clone+0x110/0x110 > [ 153.969008] ? vfs_getattr_nosec+0x14a/0x190 > [ 153.970539] ? __do_sys_newfstat+0xd6/0xf0 > [ 153.971713] ? __ia32_compat_sys_newfstat+0x40/0x40 > [ 153.973005] ? __x64_sys_io_submit+0x125/0x3b0 > [ 153.974282] ? __ia32_sys_io_submit+0x390/0x390 > [ 153.975575] ? __kasan_check_read+0x1d/0x30 > [ 153.976749] ? do_syscall_64+0x35/0x80 > [ 153.978034] ? entry_SYSCALL_64_after_hwframe+0x44/0xae > [ 153.979436] > [ 153.979738] Allocated by task 726: > [ 153.980352] kasan_save_stack+0x23/0x60 > [ 153.981054] set_alloc_info+0x46/0x70 > [ 153.981745] __kasan_slab_alloc+0x4c/0x90 > [ 153.982492] kmem_cache_alloc+0x153/0x750 > [ 153.983953] ovl_read_iter+0x13b/0x270 > [ 153.984689] aio_read+0x190/0x2d0 > [ 153.985332] io_submit_one+0xaa7/0x1480 > [ 153.986060] __x64_sys_io_submit+0x125/0x3b0 > [ 153.986878] do_syscall_64+0x35/0x80 > [ 153.987590] entry_SYSCALL_64_after_hwframe+0x44/0xae > [ 153.988516] > [ 153.988824] Freed by task 750: > [ 153.989417] kasan_save_stack+0x23/0x60 > [ 153.990140] kasan_set_track+0x24/0x40 > [ 153.990871] kasan_set_free_info+0x30/0x60 > [ 153.991639] __kasan_slab_free+0x137/0x210 > [ 153.992390] kmem_cache_free+0xf8/0x590 > [ 153.993303] ovl_aio_cleanup_handler+0x1ae/0x2a0 > [ 153.994205] ovl_aio_rw_complete+0x31/0x60 > [ 153.995043] iomap_dio_complete_work+0x4b/0x60 > [ 153.995898] iomap_dio_bio_end_io+0x23d/0x270 > [ 153.996742] bio_endio+0x40d/0x440 > [ 153.997376] blk_update_request+0x38f/0x820 > [ 153.998160] scsi_end_request+0x56/0x320 > [ 153.998872] scsi_io_completion+0x10a/0xb60 > [ 153.999655] scsi_finish_command+0x194/0x2b0 > [ 154.000464] scsi_complete+0xd7/0x1f0 > [ 154.001184] blk_complete_reqs+0x92/0xb0 > [ 154.001930] blk_done_softirq+0x29/0x40 > [ 154.002696] __do_softirq+0x133/0x57f > > ext4_dio_read_iter > ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL, 0) > file_accessed(iocb->ki_filp) <== this trigger UAF > > Ret can be -EIOCBQUEUED which means we will not wait for io completion in > iomap_dio_rw. So the release for ovl_aio_req will be done when io > completion routine call ovl_aio_rw_complete(or ovl_aio_cleanup_handler > in ovl_read_iter will do this). But once io finish soon, we may already > release ovl_aio_req before we call file_access in ext4_dio_read_iter. > This can trigger the upper UAF. > > Fix it by introduce refcount in ovl_aio_req like what aio_kiocb has did. Looks good at a glance. Will review more fully. Thanks, MIklos
