Subject: CVE-2024-26728: drm/amd/display: fix null-pointer dereference on edid reading

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

drm/amd/display: fix null-pointer dereference on edid reading

Use i2c adapter when there isn't aux_mode in dc_link to fix a
null-pointer derefence that happens when running
igt@kms_force_connector_basic in a system with DCN2.1 and HDMI connector
detected as below:

[  +0.178146] BUG: kernel NULL pointer dereference, address: 00000000000004c0
[  +0.000010] #PF: supervisor read access in kernel mode
[  +0.000005] #PF: error_code(0x0000) - not-present page
[  +0.000004] PGD 0 P4D 0
[  +0.000006] Oops: 0000 [#1] PREEMPT SMP NOPTI
[  +0.000006] CPU: 15 PID: 2368 Comm: kms_force_conne Not tainted 6.5.0-asdn+ #152
[  +0.000005] Hardware name: HP HP ENVY x360 Convertible 13-ay1xxx/8929, BIOS F.01 07/14/2021
[  +0.000004] RIP: 0010:i2c_transfer+0xd/0x100
[  +0.000011] Code: ea fc ff ff 66 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 41 54 55 53 <48> 8b 47 10 48 89 fb 48 83 38 00 0f 84 b3 00 00 00 83 3d 2f 80 16
[  +0.000004] RSP: 0018:ffff9c4f89c0fad0 EFLAGS: 00010246
[  +0.000005] RAX: 0000000000000000 RBX: 0000000000000005 RCX: 0000000000000080
[  +0.000003] RDX: 0000000000000002 RSI: ffff9c4f89c0fb20 RDI: 00000000000004b0
[  +0.000003] RBP: ffff9c4f89c0fb80 R08: 0000000000000080 R09: ffff8d8e0b15b980
[  +0.000003] R10: 00000000000380e0 R11: 0000000000000000 R12: 0000000000000080
[  +0.000002] R13: 0000000000000002 R14: ffff9c4f89c0fb0e R15: ffff9c4f89c0fb0f
[  +0.000004] FS:  00007f9ad2176c40(0000) GS:ffff8d90fe9c0000(0000) knlGS:0000000000000000
[  +0.000003] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  +0.000004] CR2: 00000000000004c0 CR3: 0000000121bc4000 CR4: 0000000000750ee0
[  +0.000003] PKRU: 55555554
[  +0.000003] Call Trace:
[  +0.000006]  <TASK>
[  +0.000006]  ? __die+0x23/0x70
[  +0.000011]  ? page_fault_oops+0x17d/0x4c0
[  +0.000008]  ? preempt_count_add+0x6e/0xa0
[  +0.000008]  ? srso_alias_return_thunk+0x5/0x7f
[  +0.000011]  ? exc_page_fault+0x7f/0x180
[  +0.000009]  ? asm_exc_page_fault+0x26/0x30
[  +0.000013]  ? i2c_transfer+0xd/0x100
[  +0.000010]  drm_do_probe_ddc_edid+0xc2/0x140 [drm]
[  +0.000067]  ? srso_alias_return_thunk+0x5/0x7f
[  +0.000006]  ? _drm_do_get_edid+0x97/0x3c0 [drm]
[  +0.000043]  ? __pfx_drm_do_probe_ddc_edid+0x10/0x10 [drm]
[  +0.000042]  edid_block_read+0x3b/0xd0 [drm]
[  +0.000043]  _drm_do_get_edid+0xb6/0x3c0 [drm]
[  +0.000041]  ? __pfx_drm_do_probe_ddc_edid+0x10/0x10 [drm]
[  +0.000043]  drm_edid_read_custom+0x37/0xd0 [drm]
[  +0.000044]  amdgpu_dm_connector_mode_valid+0x129/0x1d0 [amdgpu]
[  +0.000153]  drm_connector_mode_valid+0x3b/0x60 [drm_kms_helper]
[  +0.000000]  __drm_helper_update_and_validate+0xfe/0x3c0 [drm_kms_helper]
[  +0.000000]  ? amdgpu_dm_connector_get_modes+0xb6/0x520 [amdgpu]
[  +0.000000]  ? srso_alias_return_thunk+0x5/0x7f
[  +0.000000]  drm_helper_probe_single_connector_modes+0x2ab/0x540 [drm_kms_helper]
[  +0.000000]  status_store+0xb2/0x1f0 [drm]
[  +0.000000]  kernfs_fop_write_iter+0x136/0x1d0
[  +0.000000]  vfs_write+0x24d/0x440
[  +0.000000]  ksys_write+0x6f/0xf0
[  +0.000000]  do_syscall_64+0x60/0xc0
[  +0.000000]  ? srso_alias_return_thunk+0x5/0x7f
[  +0.000000]  ? syscall_exit_to_user_mode+0x2b/0x40
[  +0.000000]  ? srso_alias_return_thunk+0x5/0x7f
[  +0.000000]  ? do_syscall_64+0x6c/0xc0
[  +0.000000]  ? do_syscall_64+0x6c/0xc0
[  +0.000000]  entry_SYSCALL_64_after_hwframe+0x6e/0xd8
[  +0.000000] RIP: 0033:0x7f9ad46b4b00
[  +0.000000] Code: 40 00 48 8b 15 19 b3 0d 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 80 3d e1 3a 0e 00 00 74 17 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 48 83 ec 28 48 89
[  +0.000000] RSP: 002b:00007ffcbd3bd6d8 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
[  +0.000000] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f9ad46b4b00
[  +0.000000] RDX: 0000000000000002 RSI: 00007f9ad48a7417 RDI: 0000000000000009
[  +0.000000] RBP: 0000000000000002 R08: 0000000000000064 R09: 0000000000000000
[  +0.000000] R10: 0000000000000000 R11: 0000000000000202 R12: 00007f9ad48a7417
[  +0.000000] R13: 0000000000000009 R14: 00007ffcbd3bd760 R15: 0000000000000001
[  +0.000000]  </TASK>
[  +0.000000] Modules linked in: ctr ccm rfcomm snd_seq_dummy snd_hrtimer snd_seq snd_seq_device cmac algif_hash algif_skcipher af_alg bnep btusb btrtl btbcm btintel btmtk bluetooth uvcvideo videobuf2_vmalloc sha3_generic videobuf2_memops uvc jitterentropy_rng videobuf2_v4l2 videodev drbg videobuf2_common ansi_cprng mc ecdh_generic ecc qrtr binfmt_misc hid_sensor_accel_3d hid_sensor_magn_3d hid_sensor_gyro_3d hid_sensor_trigger industrialio_triggered_buffer kfifo_buf industrialio snd_ctl_led joydev hid_sensor_iio_common rtw89_8852ae rtw89_8852a rtw89_pci snd_hda_codec_realtek rtw89_core snd_hda_codec_generic intel_rapl_msr ledtrig_audio intel_rapl_common snd_hda_codec_hdmi mac80211 snd_hda_intel snd_intel_dspcfg kvm_amd snd_hda_codec snd_soc_dmic snd_acp3x_rn snd_acp3x_pdm_dma libarc4 snd_hwdep snd_soc_core kvm snd_hda_core cfg80211 snd_pci_acp6x snd_pcm nls_ascii snd_timer hp_wmi snd_pci_acp5x nls_cp437 snd_rn_pci_acp3x ucsi_acpi sparse_keymap ccp snd platform_profile snd_acp_config typec_ucsi irqbypass vfat sp5100_tco
[  +0.000000]  snd_soc_acpi fat rapl pcspkr wmi_bmof roles rfkill rng_core snd_pci_acp3x soundcore k10temp watchdog typec battery ac amd_pmc acpi_tad button hid_sensor_hub hid_multitouch evdev serio_raw msr parport_pc ppdev lp parport fuse loop efi_pstore configfs ip_tables x_tables autofs4 ext4 crc16 mbcache jbd2 btrfs blake2b_generic dm_crypt dm_mod efivarfs raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx libcrc32c crc32c_generic xor raid6_pq raid1 raid0 multipath linear md_mod amdgpu amdxcp i2c_algo_bit drm_ttm_helper ttm crc32_pclmul crc32c_intel drm_exec gpu_sched drm_suballoc_helper nvme ghash_clmulni_intel drm_buddy drm_display_helper sha512_ssse3 nvme_core ahci xhci_pci sha512_generic hid_generic xhci_hcd libahci rtsx_pci_sdmmc t10_pi i2c_hid_acpi drm_kms_helper i2c_hid mmc_core libata aesni_intel crc64_rocksoft_generic crypto_simd amd_sfh crc64_rocksoft scsi_mod usbcore cryptd crc_t10dif cec drm crct10dif_generic hid rtsx_pci crct10dif_pclmul scsi_common rc_core crc64 i2c_piix4
[  +0.000000]  usb_common crct10dif_common video wmi
[  +0.000000] CR2: 00000000000004c0
[  +0.000000] ---[ end trace 0000000000000000 ]---

The Linux kernel CVE team has assigned CVE-2024-26728 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 6.7 with commit 0e859faf8670 and fixed in 6.7.7 with commit 2d392f7268a1
	Issue introduced in 6.7 with commit 0e859faf8670 and fixed in 6.8 with commit 967176179215

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-26728
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/2d392f7268a1a9bfbd98c831f0f4c964e59aa145
	https://git.kernel.org/stable/c/9671761792156f2339627918bafcd713a8a6f777