CVE-2022-49070
Vulnérabilité moyenne dans Linux (Linux)
Description
In the Linux kernel, the following vulnerability has been resolved: fbdev: Fix unregistering of framebuffers without device OF framebuffers do not have an underlying device in the Linux device hierarchy. Do a regular unregister call instead of hot unplugging such a non-existing device. Fixes a NULL dereference. An example error message on ppc64le is shown below. BUG: Kernel NULL pointer dereference on read at 0x00000060 Faulting instruction address: 0xc00000000080dfa4 Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries [...] CPU: 2 PID: 139 Comm: systemd-udevd Not tainted 5.17.0-ae085d7f9365 #1 NIP: c00000000080dfa4 LR: c00000000080df9c CTR: c000000000797430 REGS: c000000004132fe0 TRAP: 0300 Not tainted (5.17.0-ae085d7f9365) MSR: 8000000002009033 <SF,VEC,EE,ME,IR,DR,RI,LE> CR: 28228282 XER: 20000000 CFAR: c00000000000c80c DAR: 0000000000000060 DSISR: 40000000 IRQMASK: 0 GPR00: c00000000080df9c c000000004133280 c00000000169d200 0000000000000029 GPR04: 00000000ffffefff c000000004132f90 c000000004132f88 0000000000000000 GPR08: c0000000015658f8 c0000000015cd200 c0000000014f57d0 0000000048228283 GPR12: 0000000000000000 c00000003fffe300 0000000020000000 0000000000000000 GPR16: 0000000000000000 0000000113fc4a40 0000000000000005 0000000113fcfb80 GPR20: 000001000f7283b0 0000000000000000 c000000000e4a588 c000000000e4a5b0 GPR24: 0000000000000001 00000000000a0000 c008000000db0168 c0000000021f6ec0 GPR28: c0000000016d65a8 c000000004b36460 0000000000000000 c0000000016d64b0 NIP [c00000000080dfa4] do_remove_conflicting_framebuffers+0x184/0x1d0 [c000000004133280] [c00000000080df9c] do_remove_conflicting_framebuffers+0x17c/0x1d0 (unreliable) [c000000004133350] [c00000000080e4d0] remove_conflicting_framebuffers+0x60/0x150 [c0000000041333a0] [c00000000080e6f4] remove_conflicting_pci_framebuffers+0x134/0x1b0 [c000000004133450] [c008000000e70438] drm_aperture_remove_conflicting_pci_framebuffers+0x90/0x100 [drm] [c000000004133490] [c008000000da0ce4] bochs_pci_probe+0x6c/0xa64 [bochs] [...] [c000000004133db0] [c00000000002aaa0] system_call_exception+0x170/0x2d0 [c000000004133e10] [c00000000000c3cc] system_call_common+0xec/0x250 The bug [1] was introduced by commit 27599aacbaef ("fbdev: Hot-unplug firmware fb devices on forced removal"). Most firmware framebuffers have an underlying platform device, which can be hot-unplugged before loading the native graphics driver. OF framebuffers do not (yet) have that device. Fix the code by unregistering the framebuffer as before without a hot unplug. Tested with 5.17 on qemu ppc64le emulation.
Gravité et risque d'exploitation
CVE-2022-49070 obtient un score CVSS de 5.5/10, soit une gravité moyenne. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.26 %, ce qui la place devant 16.7 % des CVE référencées.
Que faire ?
- Vérifiez si Linux (versions 5.15.33, <2388f826cdc9af2651991adc0feb79de9bdf2232, 5.17.2, <0f525289ff0ddeb380813bd81e0f9bdaaa1c9078, c894ac44786cfed383a6c6b20c1bfb12eb96018a, 4d695d7c276f15adb1d2b64c584c3cf8f4f9e9ce, <5.16.20, 5.16.19, <de33df481545974ba47c46f05194e769e4307843, 27599aacbaefcbf2af7b06b0029459bbf682000d, <5.15.34, 9565a3b5203a4d57acbc1d0e981c6df71864b4ab, <feed87ff122b1640c221d4dd559442ab2cd50bb1, <5.17.3) est présent sur votre parc.
- Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
- À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
- Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.