{ "schema_version": "1.6.1", "id": "RPI-CVE-2024-35877", "modified": "2026-10-07T17:22:01Z", "upstream": [ "CVE-2024-35877" ], "published": "2024-05-19T08:35:32Z", "summary": "x86/mm/pat: fix VM_PAT handling in COW mappings", "details": "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 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 \n #include \n #include \n #include \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] \n[ 301.566325] ? untrack_pfn+0xf4/0x100\n[ 301.566618] ? __warn+0x81/0x130\n[ 301.566876] ? untrack_pfn+0xf4/0x100\n[ 3\n---truncated---", "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.1.21-1+rpt1", "1:6.1.47-1+rpt2", "1:6.1.47-1+rpt4", "1:6.1.54-1+rpt2", "1:6.1.58-1+rpt2", "1:6.1.63-1+rpt1", "1:6.1.73-1+rpt1", "1:6.6.20-1+rpt1" ], "ecosystem_specific": { "binaries": [ { 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"url": "https://www.cve.org/CVERecord?id=CVE-2024-35877" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/f18681daaec9665a15c5e7e0f591aad5d0ac622b" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/09e6bb53217bf388a0d2fd7fb21e74ab9dffc173" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/c2b2430b48f3c9eaccd2c3d2ad75bb540d4952f4" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/7cfee26d1950250b14c5cb0a37b142f3fcc6396a" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/97e93367e82752e475a33839a80b33bdbef1209f" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/51b7841f3fe84606ec0bd8da859d22e05e5419ec" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/1341e4b32e1fb1b0acd002ccd56f07bd32f2abc6" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/04c35ab3bdae7fefbd7c7a7355f29fa03a035221" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": 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