On Tue, 28 Apr 2020 at 09:47, Hillf Danton <hdanton@xxxxxxxx> wrote: > > > 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@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > ================================================================== > > 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. > I submitted the fix after getting a confirmation from syzbot that the bad refcounting seemed to be causing this race. Please see https://patchwork.kernel.org/patch/11514431/ Thanks, Ezequiel
