Re: KASAN: use-after-free Read in vkms_dumb_create

From: Ezequiel Garcia
Date: Tue Apr 28 2020 - 14:59:24 EST

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In reply to: syzbot: "Re: KASAN: use-after-free Read in vkms_dumb_create"
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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

Next message: Greg Kroah-Hartman: "[PATCH 4.19 005/131] vti4: removed duplicate log message."
Previous message: Greg Kroah-Hartman: "[PATCH 5.6 066/167] net: dsa: b53: Fix valid setting for MDB entries"
In reply to: syzbot: "Re: KASAN: use-after-free Read in vkms_dumb_create"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]