{"id":"CVE-2026-74449","state":"PUBLISHED","title":"drm/amd/display: Fix divide-by-zero in calculate_mcache_setting on zero viewport","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/amd/display: Fix divide-by-zero in calculate_mcache_setting on zero viewport\n\nIf a plane reaches calculate_mcache_setting with a zero-area viewport,\ncalculate_mcache_setting exits early with num_mcaches == 0 and\nmvmpg_width/height == 0. This will cause a divide-by-zero panic and can\nalso cause an underflow on num_mcaches.\n\nFix this by changing calculate_mcache_setting to bool and adding guards\nafter each calculate_mcache_row_bytes call. If num_mcaches or\nmvmpg_width/height is zero, return a false. Callers will propagate the\nfailure as a rejected mode, which prevents the panic.\n\n(cherry picked from commit 29c0f7c655f47bcbd575ff75e58480df6ec3c9da)","publishedAt":"2026-08-15T12:26:54.519Z","updatedAt":"2026-10-21T12:45:40.556Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"70839da6360500a82e4d5f78499284474cbed7c1","status":"affected","lessThan":"70f5f4ddba0d2d89e77ec13b79cdcfbef33be0d9","versionType":"git"},{"version":"70839da6360500a82e4d5f78499284474cbed7c1","status":"affected","lessThan":"23a541c31b45fa813b33269376f6bd53535429a8","versionType":"git"},{"version":"70839da6360500a82e4d5f78499284474cbed7c1","status":"affected","lessThan":"1f93537881fd22712732a60ad12572a3fd40c0ec","versionType":"git"},{"version":"70839da6360500a82e4d5f78499284474cbed7c1","status":"affected","lessThan":"f327e389c07cfc3a2f6ff54f6214e1a52d457edc","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_core/dml2_core_dcn4_calcs.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.11","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.11","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.57","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.8","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_core/dml2_core_dcn4_calcs.c"]}],"references":["https://git.kernel.org/stable/c/70f5f4ddba0d2d89e77ec13b79cdcfbef33be0d9","https://git.kernel.org/stable/c/23a541c31b45fa813b33269376f6bd53535429a8","https://git.kernel.org/stable/c/1f93537881fd22712732a60ad12572a3fd40c0ec","https://git.kernel.org/stable/c/f327e389c07cfc3a2f6ff54f6214e1a52d457edc"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/74xxx/CVE-2026-74449.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-74449","state":"PUBLISHED","datePublished":"2026-08-15T12:26:54.519Z","dateUpdated":"2026-10-21T12:45:40.556Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-15T05:44:03.899Z"},"containers":{"cna":{"title":"drm/amd/display: Fix divide-by-zero in calculate_mcache_setting on zero viewport","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/amd/display: Fix divide-by-zero in calculate_mcache_setting on zero viewport\n\nIf a plane reaches calculate_mcache_setting with a zero-area viewport,\ncalculate_mcache_setting exits early with num_mcaches == 0 and\nmvmpg_width/height == 0. This will cause a divide-by-zero panic and can\nalso cause an underflow on num_mcaches.\n\nFix this by changing calculate_mcache_setting to bool and adding guards\nafter each calculate_mcache_row_bytes call. If num_mcaches or\nmvmpg_width/height is zero, return a false. Callers will propagate the\nfailure as a rejected mode, which prevents the panic.\n\n(cherry picked from commit 29c0f7c655f47bcbd575ff75e58480df6ec3c9da)"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"70839da6360500a82e4d5f78499284474cbed7c1","status":"affected","lessThan":"70f5f4ddba0d2d89e77ec13b79cdcfbef33be0d9","versionType":"git"},{"version":"70839da6360500a82e4d5f78499284474cbed7c1","status":"affected","lessThan":"23a541c31b45fa813b33269376f6bd53535429a8","versionType":"git"},{"version":"70839da6360500a82e4d5f78499284474cbed7c1","status":"affected","lessThan":"1f93537881fd22712732a60ad12572a3fd40c0ec","versionType":"git"},{"version":"70839da6360500a82e4d5f78499284474cbed7c1","status":"affected","lessThan":"f327e389c07cfc3a2f6ff54f6214e1a52d457edc","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_core/dml2_core_dcn4_calcs.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.11","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.11","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.57","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.8","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_core/dml2_core_dcn4_calcs.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/70f5f4ddba0d2d89e77ec13b79cdcfbef33be0d9"},{"url":"https://git.kernel.org/stable/c/23a541c31b45fa813b33269376f6bd53535429a8"},{"url":"https://git.kernel.org/stable/c/1f93537881fd22712732a60ad12572a3fd40c0ec"},{"url":"https://git.kernel.org/stable/c/f327e389c07cfc3a2f6ff54f6214e1a52d457edc"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The bug is reached during DRM atomic display validation on AMDGPU DCN4.x (dml21 path): userspace ioctl → amdgpu_dm atomic commit → dc_validate_global_state/dc_validate_with_context → dcn401/dcn42_validate_bandwidth → dml2_validate → dml21_validate → dml2_check_mode_supported → dml2_core_calcs_mode_support_ex → calculate_mcache_setting; no network or physical bus is involved.\nAC:L - An attacker with DRM card access can submit atomic commits that configure DCC-enabled planes and repeatedly probe scaler/viewport edge cases (including degenerate zero-area viewports or zero mvmpg dimensions) to reach calculate_mcache_setting; once triggered, num_mcaches==0 deterministically underflows loop bounds and causes divide-by-zero without races or uncontrollable heap layout.\nPR:L - Exploitation requires only standard local DRM display privileges to perform atomic modeset ioctl on /dev/dri/card* (typical for session-owning desktop users in the video/render group), not init-namespace root/CAP_SYS_ADMIN; user namespaces do not grant independent access to the host GPU display stack.\nUI:N - No victim interaction is required beyond the attacker issuing their own DRM atomic commit to configure a plane with DCC compression enabled; the kernel panic/corruption occurs during in-kernel DML bandwidth validation, not from another user opening files or mounting filesystems.\nS:U - The vulnerability corrupts kernel memory and can enable local privilege escalation within the same host kernel running the AMDGPU display driver; it does not cross a VM, IOMMU, or sandbox boundary such as KVM guest-to-host escape.\nC:H - When num_mcaches is zero, unsigned underflow in loop bounds (n < *num_mcaches_l - 1) and indexing (mcache_offsets_l[*num_mcaches_l - 1]) performs massive out-of-bounds reads/writes past the fixed-size mcache_offsets arrays in kernel DML state, enabling disclosure of adjacent kernel heap memory rather than a pure crash with no data exposure.\nI:H - The same num_mcaches underflow drives unbounded out-of-bounds writes into mode_lib mcache offset arrays and related DML structures during calculate_mcache_setting, providing attacker-influenced kernel memory corruption primitives that could be leveraged for control-flow hijacking beyond a simple denial-of-service fault.\nA:H - The vulnerable path performs integer divide-by-zero on zero mvmpg_access_width/num_mcaches and executes out-of-bounds mcache offset writes, either of which can immediately trigger a kernel oops or panic during display mode validation, denying service to all users on affected AMD DCN4.x systems until reboot."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-21T12:45:40.556Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.11","versionEndExcluding":"6.12.114"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.11","versionEndExcluding":"6.18.57"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.11","versionEndExcluding":"7.1.8"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.11","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-74449","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T18:56:48.300764Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-16T19:05:46.407Z"}}]}}}