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Message-ID: <2025040135-CVE-2025-21939-b7d7@gregkh> Date: Tue, 1 Apr 2025 16:40:03 +0100 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-cve-announce@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org> Subject: CVE-2025-21939: drm/xe/hmm: Don't dereference struct page pointers without notifier lock Description =========== In the Linux kernel, the following vulnerability has been resolved: drm/xe/hmm: Don't dereference struct page pointers without notifier lock The pnfs that we obtain from hmm_range_fault() point to pages that we don't have a reference on, and the guarantee that they are still in the cpu page-tables is that the notifier lock must be held and the notifier seqno is still valid. So while building the sg table and marking the pages accesses / dirty we need to hold this lock with a validated seqno. However, the lock is reclaim tainted which makes sg_alloc_table_from_pages_segment() unusable, since it internally allocates memory. Instead build the sg-table manually. For the non-iommu case this might lead to fewer coalesces, but if that's a problem it can be fixed up later in the resource cursor code. For the iommu case, the whole sg-table may still be coalesced to a single contigous device va region. This avoids marking pages that we don't own dirty and accessed, and it also avoid dereferencing struct pages that we don't own. v2: - Use assert to check whether hmm pfns are valid (Matthew Auld) - Take into account that large pages may cross range boundaries (Matthew Auld) v3: - Don't unnecessarily check for a non-freed sg-table. (Matthew Auld) - Add a missing up_read() in an error path. (Matthew Auld) (cherry picked from commit ea3e66d280ce2576664a862693d1da8fd324c317) The Linux kernel CVE team has assigned CVE-2025-21939 to this issue. Affected and fixed versions =========================== Issue introduced in 6.10 with commit 81e058a3e7fd8593d076b4f26f7b8bb49f1d61e3 and fixed in 6.12.19 with commit 2a24c98f0e4cc994334598d4f3a851972064809d Issue introduced in 6.10 with commit 81e058a3e7fd8593d076b4f26f7b8bb49f1d61e3 and fixed in 6.13.7 with commit f9326f529da7298a95643c3267f1c0fdb0db55eb Issue introduced in 6.10 with commit 81e058a3e7fd8593d076b4f26f7b8bb49f1d61e3 and fixed in 6.14 with commit 0a98219bcc961edd3388960576e4353e123b4a51 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2025-21939 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: drivers/gpu/drm/xe/xe_hmm.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/2a24c98f0e4cc994334598d4f3a851972064809d https://git.kernel.org/stable/c/f9326f529da7298a95643c3267f1c0fdb0db55eb https://git.kernel.org/stable/c/0a98219bcc961edd3388960576e4353e123b4a51
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