CVE-2024-41094

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

drm/fbdev-dma: Only set smem_start is enable per module option

Only export struct fb_info.fix.smem_start if that is required by the user and the memory does not come from vmalloc().

Setting struct fb_info.fix.smem_start breaks systems where DMA memory is backed by vmalloc address space. An example error is shown below.

[ 3.536043] ------------[ cut here ]------------ [ 3.540716] virt_to_phys used for non-linear address: 000000007fc4f540 (0xffff800086001000) [ 3.552628] WARNING: CPU: 4 PID: 61 at arch/arm64/mm/physaddr.c:12 __virt_to_phys+0x68/0x98 [ 3.565455] Modules linked in: [ 3.568525] CPU: 4 PID: 61 Comm: kworker/u12:5 Not tainted 6.6.23-06226-g4986cc3e1b75-dirty #250 [ 3.577310] Hardware name: NXP i.MX95 19X19 board (DT) [ 3.582452] Workqueue: events_unbound deferred_probe_work_func [ 3.588291] pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 3.595233] pc : __virt_to_phys+0x68/0x98 [ 3.599246] lr : __virt_to_phys+0x68/0x98 [ 3.603276] sp : ffff800083603990 [ 3.677939] Call trace: [ 3.680393] __virt_to_phys+0x68/0x98 [ 3.684067] drm_fbdev_dma_helper_fb_probe+0x138/0x238 [ 3.689214] __drm_fb_helper_initial_config_and_unlock+0x2b0/0x4c0 [ 3.695385] drm_fb_helper_initial_config+0x4c/0x68 [ 3.700264] drm_fbdev_dma_client_hotplug+0x8c/0xe0 [ 3.705161] drm_client_register+0x60/0xb0 [ 3.709269] drm_fbdev_dma_setup+0x94/0x148

Additionally, DMA memory is assumed to by contiguous in physical address space, which is not guaranteed by vmalloc().

Resolve this by checking the module flag drm_leak_fbdev_smem when DRM allocated the instance of struct fb_info. Fbdev-dma then only sets smem_start only if required (via FBINFO_HIDE_SMEM_START). Also guarantee that the framebuffer is not located in vmalloc address space.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.