linux-cve-announce - CVE-2022-50390: drm/ttm: fix undefined behavior in bit shift for TTM_TT_FLAG_PRIV

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Message-ID: <2025091853-CVE-2022-50390-742c@gregkh>
Date: Thu, 18 Sep 2025 15:34:04 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-50390: drm/ttm: fix undefined behavior in bit shift for TTM_TT_FLAG_PRIV_POPULATED

From: Greg Kroah-Hartman <gregkh@...nel.org>

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

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

drm/ttm: fix undefined behavior in bit shift for TTM_TT_FLAG_PRIV_POPULATED

Shifting signed 32-bit value by 31 bits is undefined, so changing
significant bit to unsigned. The UBSAN warning calltrace like below:

UBSAN: shift-out-of-bounds in ./include/drm/ttm/ttm_tt.h:122:26
left shift of 1 by 31 places cannot be represented in type 'int'
Call Trace:
 <TASK>
 dump_stack_lvl+0x7d/0xa5
 dump_stack+0x15/0x1b
 ubsan_epilogue+0xe/0x4e
 __ubsan_handle_shift_out_of_bounds+0x1e7/0x20c
 ttm_bo_move_memcpy+0x3b4/0x460 [ttm]
 bo_driver_move+0x32/0x40 [drm_vram_helper]
 ttm_bo_handle_move_mem+0x118/0x200 [ttm]
 ttm_bo_validate+0xfa/0x220 [ttm]
 drm_gem_vram_pin_locked+0x70/0x1b0 [drm_vram_helper]
 drm_gem_vram_pin+0x48/0xb0 [drm_vram_helper]
 drm_gem_vram_plane_helper_prepare_fb+0x53/0xe0 [drm_vram_helper]
 drm_gem_vram_simple_display_pipe_prepare_fb+0x26/0x30 [drm_vram_helper]
 drm_simple_kms_plane_prepare_fb+0x4d/0xe0 [drm_kms_helper]
 drm_atomic_helper_prepare_planes+0xda/0x210 [drm_kms_helper]
 drm_atomic_helper_commit+0xc3/0x1e0 [drm_kms_helper]
 drm_atomic_commit+0x9c/0x160 [drm]
 drm_client_modeset_commit_atomic+0x33a/0x380 [drm]
 drm_client_modeset_commit_locked+0x77/0x220 [drm]
 drm_client_modeset_commit+0x31/0x60 [drm]
 __drm_fb_helper_restore_fbdev_mode_unlocked+0xa7/0x170 [drm_kms_helper]
 drm_fb_helper_set_par+0x51/0x90 [drm_kms_helper]
 fbcon_init+0x316/0x790
 visual_init+0x113/0x1d0
 do_bind_con_driver+0x2a3/0x5c0
 do_take_over_console+0xa9/0x270
 do_fbcon_takeover+0xa1/0x170
 do_fb_registered+0x2a8/0x340
 fbcon_fb_registered+0x47/0xe0
 register_framebuffer+0x294/0x4a0
 __drm_fb_helper_initial_config_and_unlock+0x43c/0x880 [drm_kms_helper]
 drm_fb_helper_initial_config+0x52/0x80 [drm_kms_helper]
 drm_fbdev_client_hotplug+0x156/0x1b0 [drm_kms_helper]
 drm_fbdev_generic_setup+0xfc/0x290 [drm_kms_helper]
 bochs_pci_probe+0x6ca/0x772 [bochs]
 local_pci_probe+0x4d/0xb0
 pci_device_probe+0x119/0x320
 really_probe+0x181/0x550
 __driver_probe_device+0xc6/0x220
 driver_probe_device+0x32/0x100
 __driver_attach+0x195/0x200
 bus_for_each_dev+0xbb/0x120
 driver_attach+0x27/0x30
 bus_add_driver+0x22e/0x2f0
 driver_register+0xa9/0x190
 __pci_register_driver+0x90/0xa0
 bochs_pci_driver_init+0x52/0x1000 [bochs]
 do_one_initcall+0x76/0x430
 do_init_module+0x61/0x28a
 load_module+0x1f82/0x2e50
 __do_sys_finit_module+0xf8/0x190
 __x64_sys_finit_module+0x23/0x30
 do_syscall_64+0x58/0x80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
 </TASK>

The Linux kernel CVE team has assigned CVE-2022-50390 to this issue.


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

	Issue introduced in 5.10 with commit 3312be8f6fc8a8dc7cef01986dbd436eab7af0f7 and fixed in 6.0.16 with commit 2ff0309b73d86e8591881ac035af06e01c112e89
	Issue introduced in 5.10 with commit 3312be8f6fc8a8dc7cef01986dbd436eab7af0f7 and fixed in 6.1.2 with commit 6528971fdce0dfc0a28fec42c151a1eccdabadf5
	Issue introduced in 5.10 with commit 3312be8f6fc8a8dc7cef01986dbd436eab7af0f7 and fixed in 6.2 with commit 387659939c00156f8d6bab0fbc55b4eaf2b6bc5b

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-2022-50390
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:
	include/drm/ttm/ttm_tt.h


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/2ff0309b73d86e8591881ac035af06e01c112e89
	https://git.kernel.org/stable/c/6528971fdce0dfc0a28fec42c151a1eccdabadf5
	https://git.kernel.org/stable/c/387659939c00156f8d6bab0fbc55b4eaf2b6bc5b