On Fri, Jun 25, 2021 at 10:52 AM Hillf Danton <hdanton@xxxxxxxx> wrote: > > On Thu, 24 Jun 2021 21:53:15 -0700 > > syzbot found the following issue on: > > > > HEAD commit: a1f92694 Add linux-next specific files for 20210518 > > git tree: linux-next > > console output: https://syzkaller.appspot.com/x/log.txt?x=12cb6184300000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=d612e75ffd53a6d3 > > dashboard link: https://syzkaller.appspot.com/bug?extid=19c5a4b75931e8d63aab > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13f87f20300000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11f82d34300000 > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+19c5a4b75931e8d63aab@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > ================================================================== > > BUG: KASAN: use-after-free in v4l2_ioctl+0x1f1/0x250 drivers/media/v4l2-core/v4l2-dev.c:364 > > Read of size 8 at addr ffff88801dc54398 by task v4l_id/25000 > > > > CPU: 0 PID: 25000 Comm: v4l_id Not tainted 5.13.0-rc2-next-20210518-syzkaller #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > Call Trace: > > __dump_stack lib/dump_stack.c:88 [inline] > > dump_stack_lvl+0x13e/0x1d6 lib/dump_stack.c:129 > > print_address_description.constprop.0.cold+0x6c/0x309 mm/kasan/report.c:233 > > __kasan_report mm/kasan/report.c:419 [inline] > > kasan_report.cold+0x83/0xdf mm/kasan/report.c:436 > > v4l2_ioctl+0x1f1/0x250 drivers/media/v4l2-core/v4l2-dev.c:364 > > vfs_ioctl fs/ioctl.c:51 [inline] > > __do_sys_ioctl fs/ioctl.c:1069 [inline] > > __se_sys_ioctl fs/ioctl.c:1055 [inline] > > __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:1055 > > do_syscall_64+0x31/0xb0 arch/x86/entry/common.c:47 > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > RIP: 0033:0x7f30112bb017 > > Code: 00 00 00 48 8b 05 81 7e 2b 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 51 7e 2b 00 f7 d8 64 89 01 48 > > RSP: 002b:00007ffcfc119d68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f30112bb017 > > RDX: 00007ffcfc119d70 RSI: 0000000080685600 RDI: 0000000000000003 > > RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000 > > R10: 0000000000000002 R11: 0000000000000246 R12: 000055f2227cb8d0 > > R13: 00007ffcfc119ed0 R14: 0000000000000000 R15: 0000000000000000 > > > > Allocated by task 12321: > > kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38 > > kasan_set_track mm/kasan/common.c:46 [inline] > > set_alloc_info mm/kasan/common.c:431 [inline] > > ____kasan_kmalloc mm/kasan/common.c:510 [inline] > > ____kasan_kmalloc mm/kasan/common.c:469 [inline] > > __kasan_kmalloc+0x9b/0xd0 mm/kasan/common.c:519 > > kmalloc include/linux/slab.h:590 [inline] > > kzalloc include/linux/slab.h:720 [inline] > > stk_camera_probe+0x7d/0xc50 drivers/media/usb/stkwebcam/stk-webcam.c:1281 > > usb_probe_interface+0x315/0x7f0 drivers/usb/core/driver.c:396 > > really_probe+0x291/0xf60 drivers/base/dd.c:576 > > driver_probe_device+0x298/0x410 drivers/base/dd.c:763 > > __device_attach_driver+0x203/0x2c0 drivers/base/dd.c:870 > > bus_for_each_drv+0x15f/0x1e0 drivers/base/bus.c:431 > > __device_attach+0x228/0x4a0 drivers/base/dd.c:938 > > bus_probe_device+0x1e4/0x290 drivers/base/bus.c:491 > > device_add+0xbe0/0x2100 drivers/base/core.c:3320 > > usb_set_configuration+0x113f/0x1910 drivers/usb/core/message.c:2164 > > usb_generic_driver_probe+0xba/0x100 drivers/usb/core/generic.c:238 > > usb_probe_device+0xd9/0x2c0 drivers/usb/core/driver.c:293 > > really_probe+0x291/0xf60 drivers/base/dd.c:576 > > driver_probe_device+0x298/0x410 drivers/base/dd.c:763 > > __device_attach_driver+0x203/0x2c0 drivers/base/dd.c:870 > > bus_for_each_drv+0x15f/0x1e0 drivers/base/bus.c:431 > > __device_attach+0x228/0x4a0 drivers/base/dd.c:938 > > bus_probe_device+0x1e4/0x290 drivers/base/bus.c:491 > > device_add+0xbe0/0x2100 drivers/base/core.c:3320 > > usb_new_device.cold+0x721/0x1058 drivers/usb/core/hub.c:2556 > > hub_port_connect drivers/usb/core/hub.c:5276 [inline] > > hub_port_connect_change drivers/usb/core/hub.c:5416 [inline] > > port_event drivers/usb/core/hub.c:5562 [inline] > > hub_event+0x2357/0x4330 drivers/usb/core/hub.c:5644 > > process_one_work+0x98d/0x1600 kernel/workqueue.c:2275 > > worker_thread+0x64c/0x1120 kernel/workqueue.c:2421 > > kthread+0x3b1/0x4a0 kernel/kthread.c:313 > > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 > > > > Freed by task 16814: > > kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38 > > kasan_set_track+0x1c/0x30 mm/kasan/common.c:46 > > kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:357 > > ____kasan_slab_free mm/kasan/common.c:363 [inline] > > ____kasan_slab_free mm/kasan/common.c:328 [inline] > > __kasan_slab_free+0xfb/0x130 mm/kasan/common.c:371 > > kasan_slab_free include/linux/kasan.h:212 [inline] > > slab_free_hook mm/slub.c:1623 [inline] > > slab_free_freelist_hook+0xdf/0x240 mm/slub.c:1648 > > slab_free mm/slub.c:3208 [inline] > > kfree+0xeb/0x650 mm/slub.c:4274 > > usb_unbind_interface+0x1d8/0x8d0 drivers/usb/core/driver.c:458 > > __device_release_driver+0x3bd/0x6f0 drivers/base/dd.c:1181 > > device_release_driver_internal drivers/base/dd.c:1212 [inline] > > device_release_driver+0x26/0x40 drivers/base/dd.c:1235 > > bus_remove_device+0x2eb/0x5a0 drivers/base/bus.c:533 > > device_del+0x502/0xd40 drivers/base/core.c:3508 > > usb_disable_device+0x35b/0x7b0 drivers/usb/core/message.c:1413 > > usb_disconnect.cold+0x27a/0x78e drivers/usb/core/hub.c:2219 > > hub_port_connect drivers/usb/core/hub.c:5127 [inline] > > hub_port_connect_change drivers/usb/core/hub.c:5416 [inline] > > port_event drivers/usb/core/hub.c:5562 [inline] > > hub_event+0x1c9c/0x4330 drivers/usb/core/hub.c:5644 > > process_one_work+0x98d/0x1600 kernel/workqueue.c:2275 > > worker_thread+0x64c/0x1120 kernel/workqueue.c:2421 > > kthread+0x3b1/0x4a0 kernel/kthread.c:313 > > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 > > > > The buggy address belongs to the object at ffff88801dc54000 > > which belongs to the cache kmalloc-4k of size 4096 > > The buggy address is located 920 bytes inside of > > 4096-byte region [ffff88801dc54000, ffff88801dc55000) > > The buggy address belongs to the page: > > page:ffffea0000771400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1dc50 > > head:ffffea0000771400 order:3 compound_mapcount:0 compound_pincount:0 > > flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff) > > raw: 00fff00000010200 0000000000000000 0000000100000001 ffff888011042140 > > raw: 0000000000000000 0000000000040004 00000001ffffffff 0000000000000000 > > page dumped because: kasan: bad access detected > > page_owner tracks the page as allocated > > page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 11559, ts 1619924100847, free_ts 1619644095689 > > prep_new_page mm/page_alloc.c:2377 [inline] > > get_page_from_freelist+0x125c/0x2ed0 mm/page_alloc.c:4038 > > __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5239 > > alloc_pages+0x18c/0x2a0 mm/mempolicy.c:2272 > > alloc_slab_page mm/slub.c:1686 [inline] > > allocate_slab+0x2c2/0x4c0 mm/slub.c:1826 > > new_slab mm/slub.c:1889 [inline] > > new_slab_objects mm/slub.c:2635 [inline] > > ___slab_alloc+0x4ba/0x820 mm/slub.c:2798 > > __slab_alloc.constprop.0+0xa7/0xf0 mm/slub.c:2838 > > slab_alloc_node mm/slub.c:2920 [inline] > > slab_alloc mm/slub.c:2962 [inline] > > __kmalloc+0x312/0x330 mm/slub.c:4112 > > kmalloc include/linux/slab.h:595 [inline] > > tomoyo_realpath_from_path+0xc3/0x620 security/tomoyo/realpath.c:254 > > tomoyo_get_realpath security/tomoyo/file.c:151 [inline] > > tomoyo_path_perm+0x21b/0x400 security/tomoyo/file.c:822 > > security_inode_getattr+0xcf/0x140 security/security.c:1332 > > vfs_getattr fs/stat.c:139 [inline] > > vfs_statx+0x164/0x390 fs/stat.c:207 > > vfs_fstatat fs/stat.c:225 [inline] > > vfs_lstat include/linux/fs.h:3384 [inline] > > __do_sys_newlstat+0x91/0x110 fs/stat.c:380 > > do_syscall_64+0x31/0xb0 arch/x86/entry/common.c:47 > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > page last free stack trace: > > reset_page_owner include/linux/page_owner.h:24 [inline] > > free_pages_prepare mm/page_alloc.c:1305 [inline] > > __free_pages_ok+0x4cb/0xf30 mm/page_alloc.c:1586 > > qlink_free mm/kasan/quarantine.c:146 [inline] > > qlist_free_all+0x5a/0xc0 mm/kasan/quarantine.c:165 > > kasan_quarantine_reduce+0x180/0x200 mm/kasan/quarantine.c:272 > > __kasan_slab_alloc+0x8e/0xa0 mm/kasan/common.c:441 > > kasan_slab_alloc include/linux/kasan.h:236 [inline] > > slab_post_alloc_hook mm/slab.h:512 [inline] > > slab_alloc_node mm/slub.c:2954 [inline] > > slab_alloc mm/slub.c:2962 [inline] > > kmem_cache_alloc+0x285/0x4a0 mm/slub.c:2967 > > getname_flags.part.0+0x50/0x4f0 fs/namei.c:138 > > getname_flags include/linux/audit.h:319 [inline] > > getname fs/namei.c:209 [inline] > > __do_sys_unlink fs/namei.c:4139 [inline] > > __se_sys_unlink fs/namei.c:4137 [inline] > > __x64_sys_unlink+0xb1/0x100 fs/namei.c:4137 > > do_syscall_64+0x31/0xb0 arch/x86/entry/common.c:47 > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > > > Memory state around the buggy address: > > ffff88801dc54280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ffff88801dc54300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > >ffff88801dc54380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ^ > > ffff88801dc54400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ffff88801dc54480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ================================================================== > > Given the uaf in the ioctl path, open count is needed and should be > maintained by stk and is implemented in the diff below with mutex - it > is locked at file open time, released at file release time and aquired > at disconnect time. > > This can be a quick fix to the uaf, though, lights on why the video_get(vdev) > in v4l2_open() fails to prevent stk camera from going home too early are > welcome. Is it the fault on the driver side without an eye on open count? > > +++ x/drivers/media/usb/stkwebcam/stk-webcam.c > @@ -624,8 +624,10 @@ static int v4l_stk_open(struct file *fp) > dev->first_init = 0; > > err = v4l2_fh_open(fp); > - if (!err) > + if (!err) { > usb_autopm_get_interface(dev->interface); > + mutex_trylock(&dev->free_mutex); I haven't read all of it, but doing mutex_trylock w/o checking the return value looks very fishy. Can it ever be the right thing to do?... E.g. the next line we unconditionally do mutex_unlock, are we potentially unlocking a non-locked mutex? > + } > mutex_unlock(&dev->lock); > return err; > } > @@ -633,6 +635,7 @@ static int v4l_stk_open(struct file *fp) > static int v4l_stk_release(struct file *fp) > { > struct stk_camera *dev = video_drvdata(fp); > + int rc; > > mutex_lock(&dev->lock); > if (dev->owner == fp) { > @@ -645,7 +648,9 @@ static int v4l_stk_release(struct file * > > usb_autopm_put_interface(dev->interface); > mutex_unlock(&dev->lock); > - return v4l2_fh_release(fp); > + rc = v4l2_fh_release(fp); > + mutex_unlock(&dev->free_mutex); > + return rc; > } > > static ssize_t stk_read(struct file *fp, char __user *buf, > @@ -1306,6 +1311,7 @@ static int stk_camera_probe(struct usb_i > > spin_lock_init(&dev->spinlock); > mutex_init(&dev->lock); > + mutex_init(&dev->free_mutex); > init_waitqueue_head(&dev->wait_frame); > dev->first_init = 1; /* webcam LED management */ > > @@ -1385,6 +1391,8 @@ static void stk_camera_disconnect(struct > video_unregister_device(&dev->vdev); > v4l2_ctrl_handler_free(&dev->hdl); > v4l2_device_unregister(&dev->v4l2_dev); > + mutex_lock(&dev->free_mutex); > + mutex_unlock(&dev->free_mutex); > kfree(dev); > }
