CVE-2024-35932

drm/vc4: don't check if plane->state->fb == state->fb

Severity Score

"-"

*CVSS v-

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

Track

*SSVC

Descriptions

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

drm/vc4: don't check if plane->state->fb == state->fb

Currently, when using non-blocking commits, we can see the following
kernel warning:

[ 110.908514] ------------[ cut here ]------------
[ 110.908529] refcount_t: underflow; use-after-free.
[ 110.908620] WARNING: CPU: 0 PID: 1866 at lib/refcount.c:87 refcount_dec_not_one+0xb8/0xc0
[ 110.908664] Modules linked in: rfcomm snd_seq_dummy snd_hrtimer snd_seq snd_seq_device cmac algif_hash aes_arm64 aes_generic algif_skcipher af_alg bnep hid_logitech_hidpp vc4 brcmfmac hci_uart btbcm brcmutil bluetooth snd_soc_hdmi_codec cfg80211 cec drm_display_helper drm_dma_helper drm_kms_helper snd_soc_core snd_compress snd_pcm_dmaengine fb_sys_fops sysimgblt syscopyarea sysfillrect raspberrypi_hwmon ecdh_generic ecc rfkill libaes i2c_bcm2835 binfmt_misc joydev snd_bcm2835(C) bcm2835_codec(C) bcm2835_isp(C) v4l2_mem2mem videobuf2_dma_contig snd_pcm bcm2835_v4l2(C) raspberrypi_gpiomem bcm2835_mmal_vchiq(C) videobuf2_v4l2 snd_timer videobuf2_vmalloc videobuf2_memops videobuf2_common snd videodev vc_sm_cma(C) mc hid_logitech_dj uio_pdrv_genirq uio i2c_dev drm fuse dm_mod drm_panel_orientation_quirks backlight ip_tables x_tables ipv6
[ 110.909086] CPU: 0 PID: 1866 Comm: kodi.bin Tainted: G C 6.1.66-v8+ #32
[ 110.909104] Hardware name: Raspberry Pi 3 Model B Rev 1.2 (DT)
[ 110.909114] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 110.909132] pc : refcount_dec_not_one+0xb8/0xc0
[ 110.909152] lr : refcount_dec_not_one+0xb4/0xc0
[ 110.909170] sp : ffffffc00913b9c0
[ 110.909177] x29: ffffffc00913b9c0 x28: 000000556969bbb0 x27: 000000556990df60
[ 110.909205] x26: 0000000000000002 x25: 0000000000000004 x24: ffffff8004448480
[ 110.909230] x23: ffffff800570b500 x22: ffffff802e03a7bc x21: ffffffecfca68c78
[ 110.909257] x20: ffffff8002b42000 x19: ffffff802e03a600 x18: 0000000000000000
[ 110.909283] x17: 0000000000000011 x16: ffffffffffffffff x15: 0000000000000004
[ 110.909308] x14: 0000000000000fff x13: ffffffed577e47e0 x12: 0000000000000003
[ 110.909333] x11: 0000000000000000 x10: 0000000000000027 x9 : c912d0d083728c00
[ 110.909359] x8 : c912d0d083728c00 x7 : 65646e75203a745f x6 : 746e756f63666572
[ 110.909384] x5 : ffffffed579f62ee x4 : ffffffed579eb01e x3 : 0000000000000000
[ 110.909409] x2 : 0000000000000000 x1 : ffffffc00913b750 x0 : 0000000000000001
[ 110.909434] Call trace:
[ 110.909441] refcount_dec_not_one+0xb8/0xc0
[ 110.909461] vc4_bo_dec_usecnt+0x4c/0x1b0 [vc4]
[ 110.909903] vc4_cleanup_fb+0x44/0x50 [vc4]
[ 110.910315] drm_atomic_helper_cleanup_planes+0x88/0xa4 [drm_kms_helper]
[ 110.910669] vc4_atomic_commit_tail+0x390/0x9dc [vc4]
[ 110.911079] commit_tail+0xb0/0x164 [drm_kms_helper]
[ 110.911397] drm_atomic_helper_commit+0x1d0/0x1f0 [drm_kms_helper]
[ 110.911716] drm_atomic_commit+0xb0/0xdc [drm]
[ 110.912569] drm_mode_atomic_ioctl+0x348/0x4b8 [drm]
[ 110.913330] drm_ioctl_kernel+0xec/0x15c [drm]
[ 110.914091] drm_ioctl+0x24c/0x3b0 [drm]
[ 110.914850] __arm64_sys_ioctl+0x9c/0xd4
[ 110.914873] invoke_syscall+0x4c/0x114
[ 110.914897] el0_svc_common+0xd0/0x118
[ 110.914917] do_el0_svc+0x38/0xd0
[ 110.914936] el0_svc+0x30/0x8c
[ 110.914958] el0t_64_sync_handler+0x84/0xf0
[ 110.914979] el0t_64_sync+0x18c/0x190
[ 110.914996] ---[ end trace 0000000000000000 ]---

This happens because, although `prepare_fb` and `cleanup_fb` are
perfectly balanced, we cannot guarantee consistency in the check
plane->state->fb == state->fb. This means that sometimes we can increase
the refcount in `prepare_fb` and don't decrease it in `cleanup_fb`. The
opposite can also be true.

In fact, the struct drm_plane .state shouldn't be accessed directly
but instead, the `drm_atomic_get_new_plane_state()` helper function should
be used. So, we could stick to this check, but using
`drm_atomic_get_new_plane_state()`. But actually, this check is not re
---truncated---

En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: drm/vc4: no comprobar si plano->estado->fb == estado->fb Actualmente, al usar confirmaciones sin bloqueo, podemos ver la siguiente advertencia del kernel : [110.908514] ------------[ cortar aquí ]------------ [ 110.908529] refcount_t: subdesbordamiento; uso después de la liberación. [110.908620] ADVERTENCIA: CPU: 0 PID: 1866 en lib/refcount.c:87 refcount_dec_not_one+0xb8/0xc0 [110.908664] Módulos vinculados en: rfcomm snd_seq_dummy snd_hrtimer snd_seq snd_seq_device cmac algif_hash aes _arm64 aes_generic algif_skcipher af_alg bnep hid_logitech_hidpp vc4 brcmfmac hci_uart btbcm brcmutil bluetooth snd_soc_hdmi_codec cfg80211 cec drm_display_helper drm_dma_helper drm_kms_helper snd_soc_core snd_compress snd_pcm_dmaengine fb_sys_fops sysimgblt syscopyarea sysfillrect raspberrypi_hwmon ecdh_generic ecc rfkill libaes i2c_bcm 2835 binfmt_misc joydev snd_bcm2835(C) bcm2835_codec(C) bcm2835_isp(C) v4l2_mem2mem videobuf2_dma_contig snd_pcm bcm2835_v4l2(C) raspberrypi_gpiomem bcm2835_mmal_vchiq(C) 2 snd_timer videobuf2_vmalloc videobuf2_memops videobuf2_common snd videodev vc_sm_cma(C) mc hid_logitech_dj uio_pdrv_genirq uio i2c_dev drm fuse dm_mod drm_panel_orientation_quirks retroiluminación ip_tables x_tables ipv6 [110.909086] CPU: 0 PID: 1866 Comm: kodi.bin Contaminado: GC 6.1.66 -v8+ #32 [110.909104] Nombre del hardware: Frambuesa Pi 3 Modelo B Rev 1.2 (DT) [ 110.909114] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 110.909132] pc : refcount_dec_not_one+0xb8/0xc0 [ 110.909152] lr : refcount_dec_not_one + 0xb4/0xc0 [ 110.909170] sp : ffffffc00913b9c0 [ 110.909177] x29: ffffffc00913b9c0 x28: 000000556969bbb0 x27: 000000556990df60 [ 110.909205 ] x26: 0000000000000002 x25: 00000000000000004 x24: ffffff8004448480 [ 110.909230] x23: ffffff800570b500 x22: ffffff802e03a7bc x21: [110.909257] x20: ffffff8002b42000 x19: ffffff802e03a600 x18: 0000000000000000 [ 110.909283] x17: 00000000000000011 x16: ffffffffffffffff x15: 0000000000000004 [ 110.909308] x14: 0000000000000fff x13: ffffffed577e47e0 x12: 0000000000000003 [ 110.909333] x11: 0000000000000000 x10: 00000000000000027 x9: c912d0d083728c00 [110.909359] x8: c912d0d083728c00 x7 : 65646e75203a745f x6 : 746e756f63666572 [ 110.909384] x5 : ffffffed579f62ee x4 : ffffffed579eb01e x3 : 00000000000000000 [ 110.909409] x2 : 00000000000 x1: ffffffc00913b750 x0: 0000000000000001 [110.909434] Rastreo de llamadas: [110.909441] refcount_dec_not_one+0xb8/0xc0 [110.909461] / 0x1b0 [vc4] [ 110.909903] vc4_cleanup_fb+0x44/0x50 [vc4] [ 110.910315] drm_atomic_helper_cleanup_planes+0x88/0xa4 [drm_kms_helper] [ 110.910669] 0/0x9dc [vc4] [110.911079] commit_tail+0xb0/0x164 [drm_kms_helper] [110.911397 ] drm_atomic_helper_commit+0x1d0/0x1f0 [drm_kms_helper] [ 110.911716] drm_atomic_commit+0xb0/0xdc [drm] [ 110.912569] drm_mode_atomic_ioctl+0x348/0x4b8 [drm] [ 110.913330 ] drm_ioctl_kernel+0xec/0x15c [drm] [ 110.914091] drm_ioctl+0x24c/0x3b0 [drm] [ 110.914850] __arm64_sys_ioctl+0x9c/0xd4 [ 110.914873] invoke_syscall+0x4c/0x114 [ 110.914897] el0_svc_common+0xd0/0x118 [ 110.914917] svc+0x38/0xd0 [ 110.914936] el0_svc+0x30/0x8c [ 110.914958] el0t_64_sync_handler+0x84/ 0xf0 [ 110.914979] el0t_64_sync+0x18c/0x190 [ 110.914996] ---[ end trace 0000000000000000 ]--- Esto sucede porque, aunque `prepare_fb` y `cleanup_fb` están perfectamente equilibrados, no podemos garantizar la coherencia en el plano de verificación->estado ->fb == estado->fb. Esto significa que a veces podemos aumentar el recuento en `prepare_fb` y no disminuirlo en `cleanup_fb`. Lo contrario también puede ser cierto. De hecho, no se debe acceder directamente a la estructura drm_plane .state, sino que se debe utilizar la función auxiliar `drm_atomic_get_new_plane_state()`. Entonces, podríamos ceñirnos a esta verificación, pero usando `drm_atomic_get_new_plane_state()`. Pero en realidad, esta verificación no se re---trunca---

*Credits: N/A

CVSS Scores

Attack Vector

Attack Complexity

Privileges Required

User Interaction

Scope

Confidentiality

Integrity

Availability

* Common Vulnerability Scoring System

SSVC

Decision:Track

Exploitation

None

Automatable

Tech. Impact

Partial

* Organization's Worst-case Scenario

Timeline

2024-05-17 CVE Reserved
2024-05-19 CVE Published
2024-05-20 EPSS Updated
2024-08-02 CVE Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CAPEC

References (4)

URL	Tag	Source

URL	Date	SRC

URL	Date	SRC
https://git.kernel.org/stable/c/48bfb4b03c5ff6e1fa1dc73fb915e150b0968c40	2024-04-13
https://git.kernel.org/stable/c/d6b2fe2db1d0927b2d7df5c763eba55d0e1def3c	2024-04-13
https://git.kernel.org/stable/c/5343f724c912c77541029123f47ecd3d2ea63bdd	2024-04-13
https://git.kernel.org/stable/c/5ee0d47dcf33efd8950b347dcf4d20bab12a3fa9	2024-01-11

URL	Date	SRC

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				< 6.1.86 Search vendor "Linux" for product "Linux Kernel" and version " < 6.1.86"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				< 6.6.27 Search vendor "Linux" for product "Linux Kernel" and version " < 6.6.27"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				< 6.8.6 Search vendor "Linux" for product "Linux Kernel" and version " < 6.8.6"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				< 6.9 Search vendor "Linux" for product "Linux Kernel" and version " < 6.9"		en		Affected