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When unloading driver by "modprobe -r amdgpu", one NULL pointer dereference bug occurs in ras debugfs releasing. The cause is the duplicated debugfs_remove, as drm debugfs_root dir has been cleaned up already by drm_minor_unregister. BUG: kernel NULL pointer dereference, address: 00000000000000a0 PGD 0 P4D 0 Oops: 0002 [#1] SMP PTI CPU: 11 PID: 1526 Comm: modprobe Tainted: G OE 5.6.0-guchchen #1 Hardware name: System manufacturer System Product Name/TUF Z370-PLUS GAMING II, BIOS 0411 09/21/2018 RIP: 0010:down_write+0x15/0x40 Code: eb de e8 7e 17 72 ff cc cc cc cc cc cc cc cc cc cc cc cc cc cc 0f 1f 44 00 00 53 48 89 fb e8 92 d8 ff ff 31 c0 ba 01 00 00 00 <f0> 48 0f b1 13 75 0f 65 48 8b 04 25 c0 8b 01 00 48 89 43 08 5b c3 RSP: 0018:ffffb1590386fcd0 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 00000000000000a0 RCX: 0000000000000000 RDX: 0000000000000001 RSI: ffffffff85b2fcc2 RDI: 00000000000000a0 RBP: ffffb1590386fd30 R08: ffffffff85b2fcc2 R09: 000000000002b3c0 R10: ffff97a330618c40 R11: 00000000000005f6 R12: ffff97a3481beb40 R13: 00000000000000a0 R14: ffff97a3481beb40 R15: 0000000000000000 FS: 00007fb11a717540(0000) GS:ffff97a376cc0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000000000a0 CR3: 00000004066d6006 CR4: 00000000003606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: simple_recursive_removal+0x63/0x370 ? debugfs_remove+0x60/0x60 debugfs_remove+0x40/0x60 amdgpu_ras_fini+0x82/0x230 [amdgpu] ? __kernfs_remove.part.17+0x101/0x1f0 ? kernfs_name_hash+0x12/0x80 amdgpu_device_fini+0x1c0/0x580 [amdgpu] amdgpu_driver_unload_kms+0x3e/0x70 [amdgpu] amdgpu_pci_remove+0x36/0x60 [amdgpu] pci_device_remove+0x3b/0xb0 device_release_driver_internal+0xe5/0x1c0 driver_detach+0x46/0x90 bus_remove_driver+0x58/0xd0 pci_unregister_driver+0x29/0x90 amdgpu_exit+0x11/0x25 [amdgpu] __x64_sys_delete_module+0x13d/0x210 do_syscall_64+0x5f/0x250 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Signed-off-by: Guchun Chen <guchun.chen@amd.com> Reviewed-by: Tao Zhou <tao.zhou1@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.