{"id":"CVE-2024-35877","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nx86/mm/pat: fix VM_PAT handling in COW mappings\n\nPAT handling won't do the right thing in COW mappings: the first PTE (or,\nin fact, all PTEs) can be replaced during wri…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nx86/mm/pat: fix VM_PAT handling in COW mappings\n\nPAT handling won't do the right thing in COW mappings: the first PTE (or,\nin fact, all PTEs) can be replaced during wri…","severity":"medium","cvss":5.5,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-401"],"vendor":"linux","product":"linux_kernel","affected":["linux_kernel >= 2.6.29, < 4.19.312","linux_kernel >= 4.20, < 5.4.274","linux_kernel >= 5.5, < 5.10.215","linux_kernel >= 5.11, < 5.15.155","linux_kernel >= 5.16, < 6.1.85","linux_kernel >= 6.2, < 6.6.26","linux_kernel >= 6.7, < 6.8.5","linux_kernel = 6.9","debian_linux = 10.0"],"patched":["linux_kernel 6.8.5"],"published":"2024-05-19","updated":"2026-10-15","sourceUpdated":"2026-10-15T01:17:49.317","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2024-35877","references":[{"url":"https://git.kernel.org/stable/c/04c35ab3bdae7fefbd7c7a7355f29fa03a035221","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/09e6bb53217bf388a0d2fd7fb21e74ab9dffc173","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/1341e4b32e1fb1b0acd002ccd56f07bd32f2abc6","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/51b7841f3fe84606ec0bd8da859d22e05e5419ec","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/7cfee26d1950250b14c5cb0a37b142f3fcc6396a","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/97e93367e82752e475a33839a80b33bdbef1209f","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/c2b2430b48f3c9eaccd2c3d2ad75bb540d4952f4","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/f18681daaec9665a15c5e7e0f591aad5d0ac622b","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/04c35ab3bdae7fefbd7c7a7355f29fa03a035221","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.kernel.org/stable/c/09e6bb53217bf388a0d2fd7fb21e74ab9dffc173","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.kernel.org/stable/c/1341e4b32e1fb1b0acd002ccd56f07bd32f2abc6","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.kernel.org/stable/c/51b7841f3fe84606ec0bd8da859d22e05e5419ec","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.kernel.org/stable/c/7cfee26d1950250b14c5cb0a37b142f3fcc6396a","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.kernel.org/stable/c/97e93367e82752e475a33839a80b33bdbef1209f","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.kernel.org/stable/c/c2b2430b48f3c9eaccd2c3d2ad75bb540d4952f4","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.kernel.org/stable/c/f18681daaec9665a15c5e7e0f591aad5d0ac622b","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2024/06/msg00020.html","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-265688.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}],"tags":["nvd","cve.org"],"epss":0.00254,"epssPercentile":0.16818,"ingestedAt":"2026-10-15T03:30:12.683Z","ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2025-01-16T21:13:41.454834Z"},"slug":"CVE-2024-35877","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nx86/mm/pat: fix VM_PAT handling in COW mappings\n\nPAT handling won't do the right thing in COW mappings: the first PTE (or,\nin fact, all PTEs) can be replaced during write faults to point at anon\nfolios.  Reliably recovering the correct PFN and cachemode using\nfollow_phys() from PTEs will not work in COW mappings.\n\nUsing follow_phys(), we might just get the address+protection of the anon\nfolio (which is very wrong), or fail on swap/nonswap entries, failing\nfollow_phys() and triggering a WARN_ON_ONCE() in untrack_pfn() and\ntrack_pfn_copy(), not properly calling free_pfn_range().\n\nIn free_pfn_range(), we either wouldn't call memtype_free() or would call\nit with the wrong range, possibly leaking memory.\n\nTo fix that, let's update follow_phys() to refuse returning anon folios,\nand fallback to using the stored PFN inside vma->vm_pgoff for COW mappings\nif we run into that.\n\nWe will now properly handle untrack_pfn() with COW mappings, where we\ndon't need the cachemode.  We'll have to fail fork()->track_pfn_copy() if\nthe first page was replaced by an anon folio, though: we'd have to store\nthe cachemode in the VMA to make this work, likely growing the VMA size.\n\nFor now, lets keep it simple and let track_pfn_copy() just fail in that\ncase: it would have failed in the past with swap/nonswap entries already,\nand it would have done the wrong thing with anon folios.\n\nSimple reproducer to trigger the WARN_ON_ONCE() in untrack_pfn():\n\n<--- C reproducer --->\n #include <stdio.h>\n #include <sys/mman.h>\n #include <unistd.h>\n #include <liburing.h>\n\n int main(void)\n {\n         struct io_uring_params p = {};\n         int ring_fd;\n         size_t size;\n         char *map;\n\n         ring_fd = io_uring_setup(1, &p);\n         if (ring_fd < 0) {\n                 perror(\"io_uring_setup\");\n                 return 1;\n         }\n         size = p.sq_off.array + p.sq_entries * sizeof(unsigned);\n\n         /* Map the submission queue ring MAP_PRIVATE */\n         map = mmap(0, size, PROT_READ | PROT_WRITE, MAP_PRIVATE,\n                    ring_fd, IORING_OFF_SQ_RING);\n         if (map == MAP_FAILED) {\n                 perror(\"mmap\");\n                 return 1;\n         }\n\n         /* We have at least one page. Let's COW it. */\n         *map = 0;\n         pause();\n         return 0;\n }\n<--- C reproducer --->\n\nOn a system with 16 GiB RAM and swap configured:\n # ./iouring &\n # memhog 16G\n # killall iouring\n[  301.552930] ------------[ cut here ]------------\n[  301.553285] WARNING: CPU: 7 PID: 1402 at arch/x86/mm/pat/memtype.c:1060 untrack_pfn+0xf4/0x100\n[  301.553989] Modules linked in: binfmt_misc nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_g\n[  301.558232] CPU: 7 PID: 1402 Comm: iouring Not tainted 6.7.5-100.fc38.x86_64 #1\n[  301.558772] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebu4\n[  301.559569] RIP: 0010:untrack_pfn+0xf4/0x100\n[  301.559893] Code: 75 c4 eb cf 48 8b 43 10 8b a8 e8 00 00 00 3b 6b 28 74 b8 48 8b 7b 30 e8 ea 1a f7 000\n[  301.561189] RSP: 0018:ffffba2c0377fab8 EFLAGS: 00010282\n[  301.561590] RAX: 00000000ffffffea RBX: ffff9208c8ce9cc0 RCX: 000000010455e047\n[  301.562105] RDX: 07fffffff0eb1e0a RSI: 0000000000000000 RDI: ffff9208c391d200\n[  301.562628] RBP: 0000000000000000 R08: ffffba2c0377fab8 R09: 0000000000000000\n[  301.563145] R10: ffff9208d2292d50 R11: 0000000000000002 R12: 00007fea890e0000\n[  301.563669] R13: 0000000000000000 R14: ffffba2c0377fc08 R15: 0000000000000000\n[  301.564186] FS:  0000000000000000(0000) GS:ffff920c2fbc0000(0000) knlGS:0000000000000000\n[  301.564773] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n[  301.565197] CR2: 00007fea88ee8a20 CR3: 00000001033a8000 CR4: 0000000000750ef0\n[  301.565725] PKRU: 55555554\n[  301.565944] Call Trace:\n[  301.566148]  <TASK>\n[  301.566325]  ? untrack_pfn+0xf4/0x100\n[  301.566618]  ? __warn+0x81/0x130\n[  301.566876]  ? untrack_pfn+0xf4/0x100\n[  3\n---truncated---\n\n## Affected\n\n- `linux_kernel >= 2.6.29, < 4.19.312`\n- `linux_kernel >= 4.20, < 5.4.274`\n- `linux_kernel >= 5.5, < 5.10.215`\n- `linux_kernel >= 5.11, < 5.15.155`\n- `linux_kernel >= 5.16, < 6.1.85`\n- `linux_kernel >= 6.2, < 6.6.26`\n- `linux_kernel >= 6.7, < 6.8.5`\n- `linux_kernel = 6.9`\n- `debian_linux = 10.0`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 6.8.5`","depth":"sunlit","depthScore":30,"depthScoreParts":{"impact":30.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}