Sun, 26 Apr 2020 20:48:12 -0700

syzbot found the following crash on:

HEAD commit: c578ddb3 Merge tag 'linux-kselftest-5.7-rc3' of git://git... git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=10fbf0d8100000 kernel config: https://syzkaller.appspot.com/x/.config?x=b7a70e992f2f9b68 dashboard link: https://syzkaller.appspot.com/bug?extid=e3372a2afe1e7ef04bc7 compiler: gcc (GCC) 9.0.0 20181231 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15438330100000

Bisection is inconclusive: the first bad commit could be any of:

85b5bafb drm/cma-helper: Remove drm_fb_cma_fbdev_init_with_funcs() dff1c703 drm/tinydrm: Use drm_fbdev_generic_setup() 23167fa9 drm/panel: simple: Add support for Rocktech RK070ER9427 LCD panel 9060d7f4 drm/fb-helper: Finish the generic fbdev emulation 2230ca12 dt-bindings: display: Document the EDT et* displays in one file. e896c132 drm/debugfs: Add internal client debugfs file 894a677f drm/cma-helper: Use the generic fbdev emulation aa7e6455 drm/panel: Add support for the EDT ETM0700G0BDH6 244007ec drm/pl111: Set .gem_prime_vmap and .gem_prime_mmap aad34de2 drm/panel: Add support for the EDT ETM0700G0EDH6 7a6aca49 dt-bindings: Add vendor prefix for DLC Display Co., Ltd. d536540f drm/fb-helper: Add generic fbdev emulation .fb_probe function 0ca0c827 drm/panel: simple: Add DLC DLC0700YZG-1 panel c76f0f7c drm: Begin an API for in-kernel clients 5ba57bab drm: vkms: select DRM_KMS_HELPER 5fa8e4a2 drm/panel: Make of_drm_find_panel() return an ERR_PTR() instead of NULL 008095e0 drm/vc4: Add support for the transposer block c59eb3cf drm/panel: Let of_drm_find_panel() return -ENODEV when the panel is disabled 1ebe99a7 drm/vc4: Call drm_atomic_helper_fake_vblank() in the commit path 2e64a174 drm/of: Make drm_of_find_panel_or_bridge() fail when the device is disabled 1b9883ea drm/vc4: Support the case where the DSI device is disabled 6fb42b66 drm/atomic: Call fake_vblank() from the generic commit_tail() helpers b0b7aa40 dt-bindings: display: Add DT bindings for BOE HV070WSA-100 panel b25c60af drm/crtc: Add a generic infrastructure to fake VBLANK events 184d3cf4 drm/vc4: Use wait_for_flip_done() instead of wait_for_vblanks() ae8cf41b drm/panel: simple: Add support for BOE HV070WSA-100 panel to simple-panel 814bde99 drm/connector: Make ->atomic_commit() optional 955f60db drm: Add support for extracting sync signal drive edge from videomode 3b39ad7a drm/panel: simple: Add newhaven, nhd-4.3-480272ef-atxl LCD 425132fd drm/connector: Pass a drm_connector_state to ->atomic_commit() a5d2ade6 drm/panel: simple: Add support for Innolux G070Y2-L01 b82c1f8f drm/atomic: Avoid connector to writeback_connector casts 03fa9aa3 dt-bindings: Add DataImage, Inc. vendor prefix 73915b2b drm/writeback: Fix the "overview" section of the doc 97ceb1fb drm/panel: simple: Add support for DataImage SCF0700C48GGU18 e22e9531 Merge drm-upstream/drm-next into drm-misc-next 3d5664f9 drm/panel: ili9881c: Fix missing assignment to error return ret a0120245 drm/crc: Only report a single overflow when a CRC fd is opened 7ad4e463 drm/panel: p079zca: Refactor panel driver to support multiple panels 8adbbb2e drm/stm: ltdc: rework reset sequence 48bd379a drm/panel: p079zca: Add variable unprepare_delay properties 7868e507 drm/stm: ltdc: filter mode pixel clock vs pad constraint 731edd4c dt-bindings: Add Innolux P097PFG panel bindings f8878bb2 drm: print plane state normalized zpos value ca52bea9 drm/atomic-helper: Use bitwise or for filling a bitmask de04a462 drm/panel: p079zca: Support Innolux P097PFG panel 2bb7a39c dt-bindings: Add vendor prefix for kingdisplay a65020d0 drm/v3d: Fix a grammar nit in the scheduler docs. 2dd4f211 drm/v3d: Add missing v3d documentation structure. ebc950fd dt-bindings: Add KINGDISPLAY KD097D04 panel bindings cd0e0ca6 drm/panel: type promotion bug in s6e8aa0_read_mtp_id() e0d01811 drm/v3d: Remove unnecessary dma_fence_ops. 624bb0c0 drm/v3d: Delay the scheduler timeout if we're still making progress. b6d83fcc drm/panel: p079zca: Use of_device_get_match_data() 408633d2 drm/v3d: use new return type vm_fault_t in v3d_gem_fault decac6b0 dt-bindings: display: sun4i-drm: Add R40 display engine compatible 0b7510d1 drm/tilcdc: Use drm_connector_has_possible_encoder() d978a94b drm/sun4i: Add R40 display engine compatible af11942e drm/sun4i: tcon-top: Cleanup clock handling f8222409 drm/msm: Use drm_connector_has_possible_encoder() 38cb8d96 drm: Add drm_connector_has_possible_encoder() da82107e drm/sun4i: tcon: Release node when traversing of graph 7a667775 dt-bindings: display: sun4i-drm: Add R40 TV TCON description 7b71ca24 drm/radeon: Use drm_connector_for_each_possible_encoder() 4a068c5c drm/sun4i: DW HDMI: Release nodes if error happens during CRTC search ddba766d drm/nouveau: Use drm_connector_for_each_possible_encoder() 98c0e348 drm/amdgpu: Use drm_connector_for_each_possible_encoder() e0f56782 drm/sun4i: mixer: Order includes alphabetically 05db311a drm/sun4i: tcon-top: Add helpers for mux switching 83aefbb8 drm: Add drm_connector_for_each_possible_encoder() 20431c05 drm/i915: Nuke intel_mst_best_encoder() 5e496566 drm/sun4i: tcon-top: Remove mux configuration at probe time 0d998891 drm/fb-helper: Eliminate the .best_encoder() usage ac1fe132 dt-bindings: display: sun4i-drm: Fix order of DW HDMI PHY compatibles 03e3ec9a drm/panel: simple: Add Sharp LQ035Q7DB03 panel support c91b007e drm/vkms: Add extra information about vkms 5685ca0c drm/tinydrm: Fix doc build warnings 854502fa drm/vkms: Add basic CRTC initialization ae61f61f drm/client: Fix: drm_client_new: Don't require DRM to be registered c04372ea drm/vkms: Add mode_config initialization 41111ce1 drm/vkms: vkms_driver can be static 559e50fd drm/vkms: Add dumb operations 1c7c5fd9 drm/vkms: Introduce basic VKMS driver 657cd71e drm: gma500: Changed __attribute__((packed)) to __packed d1648930 drm/vkms: Add connectors helpers

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17b65cdfe00000

IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+e3372a2afe1e7ef04bc7@syzkaller.appspotmail.com

================================================================== BUG: KASAN: use-after-free in vkms_dumb_create+0x286/0x290 drivers/gpu/drm/vkms/vkms_gem.c:142 Read of size 8 at addr ffff88809e537110 by task syz-executor.0/9558

CPU: 0 PID: 9558 Comm: syz-executor.0 Not tainted 5.7.0-rc2-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x188/0x20d lib/dump_stack.c:118 print_address_description.constprop.0.cold+0xd3/0x315 mm/kasan/report.c:382 __kasan_report.cold+0x35/0x4d mm/kasan/report.c:511 kasan_report+0x33/0x50 mm/kasan/common.c:625 vkms_dumb_create+0x286/0x290 drivers/gpu/drm/vkms/vkms_gem.c:142 drm_mode_create_dumb+0x27c/0x300 drivers/gpu/drm/drm_dumb_buffers.c:94 drm_ioctl_kernel+0x220/0x2f0 drivers/gpu/drm/drm_ioctl.c:787 drm_ioctl+0x4c9/0x980 drivers/gpu/drm/drm_ioctl.c:887 vfs_ioctl fs/ioctl.c:47 [inline] ksys_ioctl+0x11a/0x180 fs/ioctl.c:763 __do_sys_ioctl fs/ioctl.c:772 [inline] __se_sys_ioctl fs/ioctl.c:770 [inline] __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:770 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xb3 RIP: 0033:0x45c829 Code: 0d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 db b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f19a3e30c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000004e2d80 RCX: 000000000045c829 RDX: 0000000020000080 RSI: 00000000c02064b2 RDI: 0000000000000003 RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 000000000000028b R14: 00000000004d3188 R15: 00007f19a3e316d4

Allocated by task 9558: save_stack+0x1b/0x40 mm/kasan/common.c:49 set_track mm/kasan/common.c:57 [inline] __kasan_kmalloc mm/kasan/common.c:495 [inline] __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:468 kmem_cache_alloc_trace+0x153/0x7d0 mm/slab.c:3551 __vkms_gem_create+0x44/0xf0 include/linux/slab.h:555 vkms_gem_create drivers/gpu/drm/vkms/vkms_gem.c:111 [inline] vkms_gem_create drivers/gpu/drm/vkms/vkms_gem.c:100 [inline] vkms_dumb_create+0x110/0x290 drivers/gpu/drm/vkms/vkms_gem.c:138 drm_mode_create_dumb+0x27c/0x300 drivers/gpu/drm/drm_dumb_buffers.c:94 drm_ioctl_kernel+0x220/0x2f0 drivers/gpu/drm/drm_ioctl.c:787 drm_ioctl+0x4c9/0x980 drivers/gpu/drm/drm_ioctl.c:887 vfs_ioctl fs/ioctl.c:47 [inline] ksys_ioctl+0x11a/0x180 fs/ioctl.c:763 __do_sys_ioctl fs/ioctl.c:772 [inline] __se_sys_ioctl fs/ioctl.c:770 [inline] __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:770 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xb3

Freed by task 9558: save_stack+0x1b/0x40 mm/kasan/common.c:49 set_track mm/kasan/common.c:57 [inline] kasan_set_free_info mm/kasan/common.c:317 [inline] __kasan_slab_free+0xf7/0x140 mm/kasan/common.c:456 __cache_free mm/slab.c:3426 [inline] kfree+0x109/0x2b0 mm/slab.c:3757 drm_gem_object_free+0xf0/0x1f0 drivers/gpu/drm/drm_gem.c:983 kref_put include/linux/kref.h:65 [inline] drm_gem_object_put_unlocked drivers/gpu/drm/drm_gem.c:1017 [inline] drm_gem_object_put_unlocked+0x190/0x1c0 drivers/gpu/drm/drm_gem.c:1002 vkms_gem_create drivers/gpu/drm/vkms/vkms_gem.c:116 [inline] vkms_gem_create drivers/gpu/drm/vkms/vkms_gem.c:100 [inline] vkms_dumb_create+0x14d/0x290 drivers/gpu/drm/vkms/vkms_gem.c:138 drm_mode_create_dumb+0x27c/0x300 drivers/gpu/drm/drm_dumb_buffers.c:94 drm_ioctl_kernel+0x220/0x2f0 drivers/gpu/drm/drm_ioctl.c:787 drm_ioctl+0x4c9/0x980 drivers/gpu/drm/drm_ioctl.c:887 vfs_ioctl fs/ioctl.c:47 [inline] ksys_ioctl+0x11a/0x180 fs/ioctl.c:763 __do_sys_ioctl fs/ioctl.c:772 [inline] __se_sys_ioctl fs/ioctl.c:770 [inline] __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:770 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xb3

The buggy address belongs to the object at ffff88809e537000 which belongs to the cache kmalloc-1k of size 1024 The buggy address is located 272 bytes inside of 1024-byte region [ffff88809e537000, ffff88809e537400) The buggy address belongs to the page: page:ffffea0002794dc0 refcount:1 mapcount:0 mapping:00000000e8234a18 index:0x0 flags: 0xfffe0000000200(slab) raw: 00fffe0000000200 ffffea00027a3608 ffffea0002749008 ffff8880aa000c40 raw: 0000000000000000 ffff88809e537000 0000000100000002 0000000000000000 page dumped because: kasan: bad access detected

Memory state around the buggy address: ffff88809e537000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88809e537080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

...

ffff88809e537100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

                     ^

ffff88809e537180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88809e537200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================

Nothing to do if we're allowed to do nothing in the error case.

--- a/drivers/gpu/drm/vkms/vkms_gem.c +++ b/drivers/gpu/drm/vkms/vkms_gem.c @@ -113,7 +113,6 @@ struct drm_gem_object *vkms_gem_create(s return ERR_CAST(obj);

ret = drm_gem_handle_create(file, &obj->gem, handle); - drm_gem_object_put_unlocked(&obj->gem); if (ret) return ERR_PTR(ret);