linux-kernel - Re: [PATCH] drm/amdgpu: Fix a null pointer access when the smc

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Message-ID: <CADnq5_P-fxbkGbzDAys+pob-mdDJOX0QZYVsVvS=7FyGZukjOQ@mail.gmail.com>
Date:   Mon, 23 Oct 2023 16:27:34 -0400
From:   Alex Deucher <alexdeucher@...il.com>
To:     qu.huang@...ux.dev
Cc:     alexander.deucher@....com, tom.stdenis@....com,
        Praful.Swarnakar@....com, srinivasan.shanmugam@....com,
        suhui@...china.com, Xinhui.Pan@....com,
        Harish.Kasiviswanathan@....com, linux-kernel@...r.kernel.org,
        amd-gfx@...ts.freedesktop.org, sumit.semwal@...aro.org,
        linaro-mm-sig@...ts.linaro.org, le.ma@....com,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        victorchengchi.lu@....com, christian.koenig@....com,
        dan.carpenter@...aro.org, Hawking.Zhang@....com
Subject: Re: [PATCH] drm/amdgpu: Fix a null pointer access when the smc_rreg
 pointer is NULL

Applied.  Thanks!

Alex

On Mon, Oct 23, 2023 at 9:06 AM <qu.huang@...ux.dev> wrote:
>
> In certain types of chips, such as VEGA20, reading the amdgpu_regs_smc file could result in an abnormal null pointer access when the smc_rreg pointer is NULL. Below are the steps to reproduce this issue and the corresponding exception log:
>
> 1. Navigate to the directory: /sys/kernel/debug/dri/0
> 2. Execute command: cat amdgpu_regs_smc
> 3. Exception Log::
> [4005007.702554] BUG: kernel NULL pointer dereference, address: 0000000000000000
> [4005007.702562] #PF: supervisor instruction fetch in kernel mode
> [4005007.702567] #PF: error_code(0x0010) - not-present page
> [4005007.702570] PGD 0 P4D 0
> [4005007.702576] Oops: 0010 [#1] SMP NOPTI
> [4005007.702581] CPU: 4 PID: 62563 Comm: cat Tainted: G           OE     5.15.0-43-generic #46-Ubunt       u
> [4005007.702590] RIP: 0010:0x0
> [4005007.702598] Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
> [4005007.702600] RSP: 0018:ffffa82b46d27da0 EFLAGS: 00010206
> [4005007.702605] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffa82b46d27e68
> [4005007.702609] RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff9940656e0000
> [4005007.702612] RBP: ffffa82b46d27dd8 R08: 0000000000000000 R09: ffff994060c07980
> [4005007.702615] R10: 0000000000020000 R11: 0000000000000000 R12: 00007f5e06753000
> [4005007.702618] R13: ffff9940656e0000 R14: ffffa82b46d27e68 R15: 00007f5e06753000
> [4005007.702622] FS:  00007f5e0755b740(0000) GS:ffff99479d300000(0000) knlGS:0000000000000000
> [4005007.702626] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [4005007.702629] CR2: ffffffffffffffd6 CR3: 00000003253fc000 CR4: 00000000003506e0
> [4005007.702633] Call Trace:
> [4005007.702636]  <TASK>
> [4005007.702640]  amdgpu_debugfs_regs_smc_read+0xb0/0x120 [amdgpu]
> [4005007.703002]  full_proxy_read+0x5c/0x80
> [4005007.703011]  vfs_read+0x9f/0x1a0
> [4005007.703019]  ksys_read+0x67/0xe0
> [4005007.703023]  __x64_sys_read+0x19/0x20
> [4005007.703028]  do_syscall_64+0x5c/0xc0
> [4005007.703034]  ? do_user_addr_fault+0x1e3/0x670
> [4005007.703040]  ? exit_to_user_mode_prepare+0x37/0xb0
> [4005007.703047]  ? irqentry_exit_to_user_mode+0x9/0x20
> [4005007.703052]  ? irqentry_exit+0x19/0x30
> [4005007.703057]  ? exc_page_fault+0x89/0x160
> [4005007.703062]  ? asm_exc_page_fault+0x8/0x30
> [4005007.703068]  entry_SYSCALL_64_after_hwframe+0x44/0xae
> [4005007.703075] RIP: 0033:0x7f5e07672992
> [4005007.703079] Code: c0 e9 b2 fe ff ff 50 48 8d 3d fa b2 0c 00 e8 c5 1d 02 00 0f 1f 44 00 00 f3 0f        1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 0f 05 <48> 3d 00 f0 ff ff 77 56 c3 0f 1f 44 00 00 48 83 e       c 28 48 89 54 24
> [4005007.703083] RSP: 002b:00007ffe03097898 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
> [4005007.703088] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007f5e07672992
> [4005007.703091] RDX: 0000000000020000 RSI: 00007f5e06753000 RDI: 0000000000000003
> [4005007.703094] RBP: 00007f5e06753000 R08: 00007f5e06752010 R09: 00007f5e06752010
> [4005007.703096] R10: 0000000000000022 R11: 0000000000000246 R12: 0000000000022000
> [4005007.703099] R13: 0000000000000003 R14: 0000000000020000 R15: 0000000000020000
> [4005007.703105]  </TASK>
> [4005007.703107] Modules linked in: nf_tables libcrc32c nfnetlink algif_hash af_alg binfmt_misc nls_       iso8859_1 ipmi_ssif ast intel_rapl_msr intel_rapl_common drm_vram_helper drm_ttm_helper amd64_edac t       tm edac_mce_amd kvm_amd ccp mac_hid k10temp kvm acpi_ipmi ipmi_si rapl sch_fq_codel ipmi_devintf ipm       i_msghandler msr parport_pc ppdev lp parport mtd pstore_blk efi_pstore ramoops pstore_zone reed_solo       mon ip_tables x_tables autofs4 ib_uverbs ib_core amdgpu(OE) amddrm_ttm_helper(OE) amdttm(OE) iommu_v       2 amd_sched(OE) amdkcl(OE) drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops cec rc_core        drm igb ahci xhci_pci libahci i2c_piix4 i2c_algo_bit xhci_pci_renesas dca
> [4005007.703184] CR2: 0000000000000000
> [4005007.703188] ---[ end trace ac65a538d240da39 ]---
> [4005007.800865] RIP: 0010:0x0
> [4005007.800871] Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
> [4005007.800874] RSP: 0018:ffffa82b46d27da0 EFLAGS: 00010206
> [4005007.800878] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffa82b46d27e68
> [4005007.800881] RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff9940656e0000
> [4005007.800883] RBP: ffffa82b46d27dd8 R08: 0000000000000000 R09: ffff994060c07980
> [4005007.800886] R10: 0000000000020000 R11: 0000000000000000 R12: 00007f5e06753000
> [4005007.800888] R13: ffff9940656e0000 R14: ffffa82b46d27e68 R15: 00007f5e06753000
> [4005007.800891] FS:  00007f5e0755b740(0000) GS:ffff99479d300000(0000) knlGS:0000000000000000
> [4005007.800895] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [4005007.800898] CR2: ffffffffffffffd6 CR3: 00000003253fc000 CR4: 00000000003506e0
>
> Signed-off-by: Qu Huang <qu.huang@...ux.dev>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> index a4faea4..05405da 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> @@ -748,6 +748,9 @@ static ssize_t amdgpu_debugfs_regs_smc_read(struct file *f, char __user *buf,
>         ssize_t result = 0;
>         int r;
>
> +       if (!adev->smc_rreg)
> +               return -EPERM;
> +
>         if (size & 0x3 || *pos & 0x3)
>                 return -EINVAL;
>
> @@ -804,6 +807,9 @@ static ssize_t amdgpu_debugfs_regs_smc_write(struct file *f, const char __user *
>         ssize_t result = 0;
>         int r;
>
> +       if (!adev->smc_wreg)
> +               return -EPERM;
> +
>         if (size & 0x3 || *pos & 0x3)
>                 return -EINVAL;
>
> --
> 1.8.3.1