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

[syzbot <syzbot+e3372a2afe1e7ef04bc7@syzkaller.appspotmail.com>]

> On Mon, 27 Apr 2020 at 00:48, syzbot
> <syzbot+e3372a2afe1e7ef04bc7@syzkaller.appspotmail.com> wrote:
>>
>> Hello,
>>
>> 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
>> ==================================================================
>>
>>
>> ---
>> This bug is generated by a bot. It may contain errors.
>> See https://goo.gl/tpsmEJ for more information about syzbot.
>> syzbot engineers can be reached at syzkaller@googlegroups.com.
>>
>> syzbot will keep track of this bug report. See:
>> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
>> syzbot can test patches for this bug, for details see:
>> https://goo.gl/tpsmEJ#testing-patches
>
> Let's see if this works...
>
> #syz test: upstream c578ddb3

"upstream" does not look like a valid git repo address.

>
> From 58035231aa036d5710286e242ec9b6d1f2995c85 Mon Sep 17 00:00:00 2001
> From: Ezequiel Garcia <ezequiel@collabora.com>
> Date: Mon, 27 Apr 2020 10:15:06 -0300
> Subject: [PATCH] vkms: Hold gem object while in use
>
> Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
> ---
>  drivers/gpu/drm/vkms/vkms_gem.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/vkms/vkms_gem.c b/drivers/gpu/drm/vkms/vkms_gem.c
> index 2e01186fb943..023e6a45fbf8 100644
> --- 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(struct
> drm_device *dev,
>   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);
>
> @@ -142,6 +141,8 @@ int vkms_dumb_create(struct drm_file *file, struct
> drm_device *dev,
>   args->size = gem_obj->size;
>   args->pitch = pitch;
>
> + drm_gem_object_put_unlocked(gem_obj);
> +
>   DRM_DEBUG_DRIVER("Created object of size %lld\n", size);
>
>   return 0;
> -- 
> 2.26.0.rc2
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