CVE-2024-26728 in Linux
Summary
by MITRE • 04/03/2024
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 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]
[ +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 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
---truncated---
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Analysis
by VulDB Data Team • 08/03/2025
The vulnerability CVE-2024-26728 represents a critical null-pointer dereference within the Linux kernel's display subsystem, specifically affecting the AMD display driver component. This flaw manifests during EDID (Extended Display Identification Data) reading operations when a system employs DCN2.1 architecture with an HDMI connector. The issue arises from a logic error where the driver fails to properly handle cases where auxiliary mode (aux_mode) is not available in the dc_link structure, leading to an attempt to access a null pointer at memory address 0x4c0. The error occurs during the execution of kms_force_connector_basic test, which is part of the kernel graphics testing suite and indicates a failure in the driver's ability to correctly identify and handle display connection states.
The technical root cause of this vulnerability lies in the drm/amd/display subsystem's handling of I2C adapter usage during EDID probing. When the driver attempts to read EDID data from an HDMI connector without proper aux_mode availability, it defaults to using an I2C adapter that may not be properly initialized or validated, resulting in a null pointer dereference. The kernel oops trace shows the execution path leading to i2c_transfer function, where the null pointer access occurs, specifically when the drm_do_probe_ddc_edid function attempts to access memory that has not been properly allocated. This condition is classified as a CWE-476 Null Pointer Dereference, which directly impacts system stability and can lead to kernel panics or system crashes. The vulnerability affects systems running kernel versions that include the problematic AMD display driver code, particularly those using DCN2.1 graphics architectures.
The operational impact of this vulnerability extends beyond simple system crashes, as it can be leveraged to cause denial of service conditions in graphical environments. When triggered, the null pointer dereference results in immediate kernel panic, terminating the graphics subsystem and potentially causing the entire system to become unresponsive. Attackers could exploit this by forcing display connection validation processes or by manipulating the display state through kernel interfaces. The vulnerability affects systems using AMD graphics hardware with DCN2.1 architecture, particularly those running kernel versions that include the affected drm/amd/display driver components. This makes it a significant concern for enterprise environments and embedded systems that rely on stable graphics operations.
Mitigation strategies for this vulnerability primarily involve updating the Linux kernel to a patched version that resolves the null pointer dereference issue in the AMD display driver. System administrators should ensure that all affected systems receive the latest kernel updates, particularly those containing the fix for the drm/amd/display subsystem. The patch implemented addresses the core logic error by ensuring proper validation of I2C adapter availability before attempting EDID reading operations, preventing the null pointer dereference. Additionally, organizations should consider implementing monitoring solutions to detect potential exploitation attempts and ensure that graphics subsystems are regularly updated. The fix aligns with ATT&CK technique T1499.004, which involves system disruption through kernel-level vulnerabilities, emphasizing the importance of maintaining updated kernel components to prevent such exploitation vectors. Security teams should also review their kernel update policies to ensure rapid deployment of security patches for critical vulnerabilities like this one.