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CVE-2025-38449

Description

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

POC

Reference

No PoCs from references.

Github

- https://github.com/w4zu/Debian_security