Description
In the Linux kernel, the following vulnerability has been resolved: fbcon: always restore the old font data in fbcon_do_set_font() Commit a5a923038d70 (fbdev: fbcon: Properly revert changes when vc_resize() failed) started restoring old font data upon failure (of vc_resize()). But it performs so only for user fonts. It means that the "system"/internal fonts are not restored at all. So in result, the very first call to fbcon_do_set_font() performs no restore at all upon failing vc_resize(). This can be reproduced by Syzkaller to crash the system on the next invocation of font_get(). It's rather hard to hit the allocation failure in vc_resize() on the first font_set(), but not impossible. Esp. if fault injection is used to aid the execution/failure. It was demonstrated by Sirius: BUG: unable to handle page fault for address: fffffffffffffff8 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD cb7b067 P4D cb7b067 PUD cb7d067 PMD 0 Oops: 0000 [#1] PREEMPT SMP KASAN CPU: 1 PID: 8007 Comm: poc Not tainted 6.7.0-g9d1694dc91ce #20 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 RIP: 0010:fbcon_get_font+0x229/0x800 drivers/video/fbdev/core/fbcon.c:2286 Call Trace: con_font_get drivers/tty/vt/vt.c:4558 [inline] con_font_op+0x1fc/0xf20 drivers/tty/vt/vt.c:4673 vt_k_ioctl drivers/tty/vt/vt_ioctl.c:474 [inline] vt_ioctl+0x632/0x2ec0 drivers/tty/vt/vt_ioctl.c:752 tty_ioctl+0x6f8/0x1570 drivers/tty/tty_io.c:2803 vfs_ioctl fs/ioctl.c:51 [inline] ... So restore the font data in any case, not only for user fonts. Note the later 'if' is now protected by 'old_userfont' and not 'old_data' as the latter is always set now. (And it is supposed to be non-NULL. Otherwise we would see the bug above again.)
Details
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Affected Packages
| Software | From version | Fixed in |
|---|---|---|
| linux | — | 5.15.0-112.122 |
| linux-allwinner-5.19 | — | — |
| linux-aws | — | 5.15.0-1063.69 |
| linux-aws-5.0 | — | — |
| linux-aws-5.11 | — | — |
| linux-aws-5.13 | — | — |
| linux-aws-5.15 | — | 5.15.0-1063.69~20.04.1 |
| linux-aws-5.19 | — | — |
| linux-aws-5.3 | — | — |
| linux-aws-5.8 | — | — |
| linux-aws-6.2 | — | — |
| linux-aws-6.5 | — | 6.5.0-1023.23~22.04.1 |
| linux-aws-fips | — | 5.15.0-1063.69+fips1 |
| linux-azure | — | 5.15.0-1066.75 |
| linux-azure-5.11 | — | — |
| linux-azure-5.13 | — | — |
| linux-azure-5.15 | — | 5.15.0-1065.74~20.04.1 |
| linux-azure-5.19 | — | — |
| linux-azure-5.3 | — | — |
| linux-azure-5.8 | — | — |
| linux-azure-6.2 | — | — |
| linux-azure-6.5 | — | 6.5.0-1024.25~22.04.1 |
| linux-azure-edge | — | — |
| linux-azure-fde | — | — |
| linux-azure-fde-5.19 | — | — |
| linux-azure-fde-6.2 | — | — |
| linux-azure-fde-6.8 | — | — |
| linux-azure-fips | — | 5.15.0-1065.74+fips1 |
| linux-bluefield | — | — |
| linux-fips | — | 5.15.0-111.121+fips1 |
| linux-gcp | — | 5.15.0-1062.70 |
| linux-gcp-5.11 | — | — |
| linux-gcp-5.13 | — | — |
| linux-gcp-5.15 | — | 5.15.0-1062.70~20.04.1 |
| linux-gcp-5.19 | — | — |
| linux-gcp-5.3 | — | — |
| linux-gcp-5.8 | — | — |
| linux-gcp-6.2 | — | — |
| linux-gcp-6.5 | — | 6.5.0-1024.26~22.04.1 |
| linux-gcp-fips | — | 5.15.0-1062.70+fips1 |
| linux-gke | — | 5.15.0-1060.66 |
| linux-gke-4.15 | — | — |
| linux-gke-5.15 | — | — |
| linux-gke-5.4 | — | — |
| linux-gkeop | — | 5.15.0-1046.53 |
| linux-gkeop-5.15 | — | 5.15.0-1046.53~20.04.1 |
| linux-gkeop-5.4 | — | — |
| linux-hwe | — | — |
| linux-hwe-5.11 | — | — |
| linux-hwe-5.13 | — | — |
| linux-hwe-5.15 | — | 5.15.0-113.123~20.04.1 |
| linux-hwe-5.19 | — | — |
| linux-hwe-5.8 | — | — |
| linux-hwe-6.2 | — | — |
| linux-hwe-6.5 | — | 6.5.0-44.44~22.04.1 |
| linux-hwe-edge | — | — |
| linux-ibm | — | 5.15.0-1056.59 |
| linux-ibm-5.15 | — | 5.15.0-1057.60~20.04.1 |
| linux-intel-5.13 | — | — |
| linux-intel-iot-realtime | — | 5.15.0-1056.58 |
| linux-intel-iotg | — | 5.15.0-1058.64 |
| linux-intel-iotg-5.15 | — | 5.15.0-1058.64~20.04.1 |
| linux-kvm | — | 5.15.0-1060.65 |
| linux-lowlatency | — | 5.15.0-110.120 |
| linux-lowlatency-hwe-5.15 | — | 5.15.0-110.120~20.04.1 |
| linux-lowlatency-hwe-5.19 | — | — |
| linux-lowlatency-hwe-6.2 | — | — |
| linux-lowlatency-hwe-6.5 | — | 6.5.0-44.44.1~22.04.1 |
| linux-nvidia | — | 5.15.0-1058.59 |
| linux-nvidia-6.2 | — | — |
| linux-nvidia-6.5 | — | 6.5.0-1023.24 |
| linux-nvidia-tegra | — | 5.15.0-1026.26 |
| linux-nvidia-tegra-5.15 | — | 5.15.0-1027.27~20.04.1 |
| linux-nvidia-tegra-igx | — | 5.15.0-1015.15 |
| linux-oem | — | — |
| linux-oem-5.10 | — | — |
| linux-oem-5.13 | — | — |
| linux-oem-5.14 | — | — |
| linux-oem-5.17 | — | — |
| linux-oem-5.6 | — | — |
| linux-oem-6.0 | — | — |
| linux-oem-6.1 | — | — |
| linux-oem-6.5 | — | 6.5.0-1027.28 |
| linux-oracle | — | 5.15.0-1061.67 |
| linux-oracle-5.0 | — | — |
| linux-oracle-5.11 | — | — |
| linux-oracle-5.13 | — | — |
| linux-oracle-5.15 | — | 5.15.0-1061.67~20.04.1 |
| linux-oracle-5.3 | — | — |
| linux-oracle-5.8 | — | — |
| linux-oracle-6.5 | — | 6.5.0-1026.26~22.04.1 |
| linux-raspi | — | 5.15.0-1058.61 |
| linux-raspi-realtime | — | 6.8.0-2002.2 |
| linux-raspi2 | — | — |
| linux-realtime | — | 5.15.0-1064.72 |
| linux-riscv | — | — |
| linux-riscv-5.11 | — | — |
| linux-riscv-5.15 | — | 5.15.0-1059.63~20.04.1 |
| linux-riscv-5.19 | — | — |
| linux-riscv-5.8 | — | — |
| linux-riscv-6.5 | — | — |
| linux-starfive-5.19 | — | — |
| linux-starfive-6.2 | — | — |
| linux-starfive-6.5 | — | 6.5.0-1017.18~22.04.1 |
| linux-xilinx-zynqmp | — | 5.15.0-1030.34 |
References
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