CVE-2025-38449

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> drm/gem: Acquire references on GEM handles for framebuffers<br /> <br /> A GEM handle can be released while the GEM buffer object is attached<br /> to a DRM framebuffer. This leads to the release of the dma-buf backing<br /> the buffer object, if any. [1] Trying to use the framebuffer in further<br /> mode-setting operations leads to a segmentation fault. Most easily<br /> happens with driver that use shadow planes for vmap-ing the dma-buf<br /> during a page flip. An example is shown below.<br /> <br /> [ 156.791968] ------------[ cut here ]------------<br /> [ 156.796830] WARNING: CPU: 2 PID: 2255 at drivers/dma-buf/dma-buf.c:1527 dma_buf_vmap+0x224/0x430<br /> [...]<br /> [ 156.942028] RIP: 0010:dma_buf_vmap+0x224/0x430<br /> [ 157.043420] Call Trace:<br /> [ 157.045898] <br /> [ 157.048030] ? show_trace_log_lvl+0x1af/0x2c0<br /> [ 157.052436] ? show_trace_log_lvl+0x1af/0x2c0<br /> [ 157.056836] ? show_trace_log_lvl+0x1af/0x2c0<br /> [ 157.061253] ? drm_gem_shmem_vmap+0x74/0x710<br /> [ 157.065567] ? dma_buf_vmap+0x224/0x430<br /> [ 157.069446] ? __warn.cold+0x58/0xe4<br /> [ 157.073061] ? dma_buf_vmap+0x224/0x430<br /> [ 157.077111] ? report_bug+0x1dd/0x390<br /> [ 157.080842] ? handle_bug+0x5e/0xa0<br /> [ 157.084389] ? exc_invalid_op+0x14/0x50<br /> [ 157.088291] ? asm_exc_invalid_op+0x16/0x20<br /> [ 157.092548] ? dma_buf_vmap+0x224/0x430<br /> [ 157.096663] ? dma_resv_get_singleton+0x6d/0x230<br /> [ 157.101341] ? __pfx_dma_buf_vmap+0x10/0x10<br /> [ 157.105588] ? __pfx_dma_resv_get_singleton+0x10/0x10<br /> [ 157.110697] drm_gem_shmem_vmap+0x74/0x710<br /> [ 157.114866] drm_gem_vmap+0xa9/0x1b0<br /> [ 157.118763] drm_gem_vmap_unlocked+0x46/0xa0<br /> [ 157.123086] drm_gem_fb_vmap+0xab/0x300<br /> [ 157.126979] drm_atomic_helper_prepare_planes.part.0+0x487/0xb10<br /> [ 157.133032] ? lockdep_init_map_type+0x19d/0x880<br /> [ 157.137701] drm_atomic_helper_commit+0x13d/0x2e0<br /> [ 157.142671] ? drm_atomic_nonblocking_commit+0xa0/0x180<br /> [ 157.147988] drm_mode_atomic_ioctl+0x766/0xe40<br /> [...]<br /> [ 157.346424] ---[ end trace 0000000000000000 ]---<br /> <br /> Acquiring GEM handles for the framebuffer&amp;#39;s GEM buffer objects prevents<br /> this from happening. The framebuffer&amp;#39;s cleanup later puts the handle<br /> references.<br /> <br /> Commit 1a148af06000 ("drm/gem-shmem: Use dma_buf from GEM object<br /> instance") triggers the segmentation fault easily by using the dma-buf<br /> field more widely. The underlying issue with reference counting has<br /> been present before.<br /> <br /> v2:<br /> - acquire the handle instead of the BO (Christian)<br /> - fix comment style (Christian)<br /> - drop the Fixes tag (Christian)<br /> - rename err_ gotos<br /> - add missing Link tag