UBUNTU-CVE-2024-35877
In the Linux kernel, the following vulnerability has been resolved: x86/mm/pat: fix VM_PAT handling in COW mappings PAT handling won't do the right thing in COW mappings: the first PTE (or, in fact, all PTEs) can be replaced during write faults to point at anon folios. Reliably recovering the correct PFN and cachemode using follow_phys() from PTEs will not work in COW mappings. Using follow_phys(), we might just get the address+protection of the anon folio (which is very wrong), or fail on swap/nonswap entries, failing follow_phys() and triggering a WARN_ON_ONCE() in untrack_pfn() and track_pfn_copy(), not properly calling free_pfn_range(). In free_pfn_range(), we either wouldn't call memtype_free() or would call it with the wrong range, possibly leaking memory. To fix that, let's update follow_phys() to refuse returning anon folios, and fallback to using the stored PFN inside vma->vm_pgoff for COW mappings if we run into that. We will now properly handle untrack_pfn() with COW mappings, where we don't need the cachemode. We'll have to fail fork()->track_pfn_copy() if the first page was replaced by an anon folio, though: we'd have to store the cachemode in the VMA to make this work, likely growing the VMA size. For now, lets keep it simple and let track_pfn_copy() just fail in that case: it would have failed in the past with swap/nonswap entries already, and it would have done the wrong thing with anon folios. Simple reproducer to trigger the WARN_ON_ONCE() in untrack_pfn(): <--- C reproducer ---> #include <stdio.h> #include <sys/mman.h> #include <unistd.h> #include <liburing.h> int main(void) { struct io_uring_params p = {}; int ring_fd; size_t size; char *map; ring_fd = io_uring_setup(1, &p); if (ring_fd < 0) { perror("io_uring_setup"); return 1; } size = p.sq_off.array + p.sq_entries * sizeof(unsigned); /* Map the submission queue ring MAP_PRIVATE */ map = mmap(0, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, ring_fd, IORING_OFF_SQ_RING); if (map == MAP_FAILED) { perror("mmap"); return 1; } /* We have at least one page. Let's COW it. */ *map = 0; pause(); return 0; } <--- C reproducer ---> On a system with 16 GiB RAM and swap configured: # ./iouring & # memhog 16G # killall iouring [ 301.552930] ------------[ cut here ]------------ [ 301.553285] WARNING: CPU: 7 PID: 1402 at arch/x86/mm/pat/memtype.c:1060 untrack_pfn+0xf4/0x100 [ 301.553989] Modules linked in: binfmt_misc nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_g [ 301.558232] CPU: 7 PID: 1402 Comm: iouring Not tainted 6.7.5-100.fc38.x86_64 #1 [ 301.558772] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebu4 [ 301.559569] RIP: 0010:untrack_pfn+0xf4/0x100 [ 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 [ 301.561189] RSP: 0018:ffffba2c0377fab8 EFLAGS: 00010282 [ 301.561590] RAX: 00000000ffffffea RBX: ffff9208c8ce9cc0 RCX: 000000010455e047 [ 301.562105] RDX: 07fffffff0eb1e0a RSI: 0000000000000000 RDI: ffff9208c391d200 [ 301.562628] RBP: 0000000000000000 R08: ffffba2c0377fab8 R09: 0000000000000000 [ 301.563145] R10: ffff9208d2292d50 R11: 0000000000000002 R12: 00007fea890e0000 [ 301.563669] R13: 0000000000000000 R14: ffffba2c0377fc08 R15: 0000000000000000 [ 301.564186] FS: 0000000000000000(0000) GS:ffff920c2fbc0000(0000) knlGS:0000000000000000 [ 301.564773] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 301.565197] CR2: 00007fea88ee8a20 CR3: 00000001033a8000 CR4: 0000000000750ef0 [ 301.565725] PKRU: 55555554 [ 301.565944] Call Trace: [ 301.566148] <TASK> [ 301.566325] ? untrack_pfn+0xf4/0x100 [ 301.566618] ? __warn+0x81/0x130 [ 301.566876] ? untrack_pfn+0xf4/0x100 [ 3 ---truncated---
02 / AFFECTED SOFTWARE
Affected packages
11 explicit affected versions
31 explicit affected versions
45 explicit affected versions
50 explicit affected versions
6 explicit affected versions
12 explicit affected versions
19 explicit affected versions
6 explicit affected versions
54 explicit affected versions
6 explicit affected versions
40 explicit affected versions
61 explicit affected versions
51 explicit affected versions
40 explicit affected versions
10 explicit affected versions
5 explicit affected versions
47 explicit affected versions
191 explicit affected versions
7 explicit affected versions
46 explicit affected versions
1 explicit affected versions
88 explicit affected versions
13 explicit affected versions
66 explicit affected versions
2 explicit affected versions
35 explicit affected versions
7 explicit affected versions
14 explicit affected versions
18 explicit affected versions
9 explicit affected versions
97 explicit affected versions
34 explicit affected versions
6 explicit affected versions
90 explicit affected versions
13 explicit affected versions
4 explicit affected versions
23 explicit affected versions
102 explicit affected versions
9 explicit affected versions
1 explicit affected versions
21 explicit affected versions
16 explicit affected versions
10 explicit affected versions
45 explicit affected versions
7 explicit affected versions
7 explicit affected versions
12 explicit affected versions
38 explicit affected versions
12 explicit affected versions
14 explicit affected versions
7 explicit affected versions
78 explicit affected versions
12 explicit affected versions
93 explicit affected versions
101 explicit affected versions
12 explicit affected versions
89 explicit affected versions
10 explicit affected versions
2 explicit affected versions
10 explicit affected versions
168 explicit affected versions
37 explicit affected versions
101 explicit affected versions
13 explicit affected versions
10 explicit affected versions
27 explicit affected versions
1 explicit affected versions
31 explicit affected versions
26 explicit affected versions
13 explicit affected versions
6 explicit affected versions
1 explicit affected versions
29 explicit affected versions
81 explicit affected versions
13 explicit affected versions
51 explicit affected versions
1 explicit affected versions
77 explicit affected versions
49 explicit affected versions
93 explicit affected versions
11 explicit affected versions
33 explicit affected versions
23 explicit affected versions
10 explicit affected versions
95 explicit affected versions
11 explicit affected versions
12 explicit affected versions
118 explicit affected versions
7 explicit affected versions
12 explicit affected versions
92 explicit affected versions
2 explicit affected versions
39 explicit affected versions
32 explicit affected versions
111 explicit affected versions
48 explicit affected versions
131 explicit affected versions
10 explicit affected versions
26 explicit affected versions
8 explicit affected versions
27 explicit affected versions
1 explicit affected versions
8 explicit affected versions
13 explicit affected versions
7 explicit affected versions
118 explicit affected versions
51 explicit affected versions
16 explicit affected versions
51 explicit affected versions
8 explicit affected versions
40 explicit affected versions
3 explicit affected versions
72 explicit affected versions
1 explicit affected versions
2 explicit affected versions
58 explicit affected versions
51 explicit affected versions
71 explicit affected versions
5 explicit affected versions
12 explicit affected versions
37 explicit affected versions
27 explicit affected versions
23 explicit affected versions
1 explicit affected versions
1 explicit affected versions
75 explicit affected versions
1 explicit affected versions
8 explicit affected versions
12 explicit affected versions
5 explicit affected versions
2 explicit affected versions
8 explicit affected versions
1 explicit affected versions
10 explicit affected versions
4 explicit affected versions
13 explicit affected versions
81 explicit affected versions
13 explicit affected versions
45 explicit affected versions
7 explicit affected versions
73 explicit affected versions
43 explicit affected versions
10 explicit affected versions
12 explicit affected versions
12 explicit affected versions
80 explicit affected versions
44 explicit affected versions
16 explicit affected versions
3 explicit affected versions
13 explicit affected versions
26 explicit affected versions
37 explicit affected versions
37 explicit affected versions
8 explicit affected versions
14 explicit affected versions
38 explicit affected versions
40 explicit affected versions
9 explicit affected versions
40 explicit affected versions
11 explicit affected versions
145 explicit affected versions
48 explicit affected versions
7 explicit affected versions
21 explicit affected versions
78 explicit affected versions
52 explicit affected versions
122 explicit affected versions
101 explicit affected versions
4 explicit affected versions
1 explicit affected versions
1 explicit affected versions
46 explicit affected versions
94 explicit affected versions
13 explicit affected versions
43 explicit affected versions
46 explicit affected versions
125 explicit affected versions
145 explicit affected versions
10 explicit affected versions
8 explicit affected versions
3 explicit affected versions
14 explicit affected versions
81 explicit affected versions
4 explicit affected versions
70 explicit affected versions
11 explicit affected versions
1 explicit affected versions
48 explicit affected versions
2 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
In the Linux kernel, the following vulnerability has been resolved: x86/mm/pat: fix VM_PAT handling in COW mappings PAT handling won't do the right thing in COW mappings: the first PTE (or, in fact, all PTEs) can be replaced during write faults to point at anon folios. Reliably recovering the correct PFN and cachemode using follow_phys() from PTEs will not work in COW mappings. Using follow_phys(), we might just get the address+protection of the anon folio (which is very wrong), or fail on swap/nonswap entries, failing follow_phys() and triggering a WARN_ON_ONCE() in untrack_pfn() and track_pfn_copy(), not properly calling free_pfn_range(). In free_pfn_range(), we either wouldn't call memtype_free() or would call it with the wrong range, possibly leaking memory. To fix that, let's update follow_phys() to refuse returning anon folios, and fallback to using the stored PFN inside vma->vm_pgoff for COW mappings if we run into that. We will now properly handle untrack_pfn() with COW mappings, where we don't need the cachemode. We'll have to fail fork()->track_pfn_copy() if the first page was replaced by an anon folio, though: we'd have to store the cachemode in the VMA to make this work, likely growing the VMA size. For now, lets keep it simple and let track_pfn_copy() just fail in that case: it would have failed in the past with swap/nonswap entries already, and it would have done the wrong thing with anon folios. Simple reproducer to trigger the WARN_ON_ONCE() in untrack_pfn(): <--- C reproducer ---> #include <stdio.h> #include <sys/mman.h> #include <unistd.h> #include <liburing.h> int main(void) { struct io_uring_params p = {}; int ring_fd; size_t size; char *map; ring_fd = io_uring_setup(1, &p); if (ring_fd < 0) { perror("io_uring_setup"); return 1; } size = p.sq_off.array + p.sq_entries * sizeof(unsigned); /* Map the submission queue ring MAP_PRIVATE */ map = mmap(0, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, ring_fd, IORING_OFF_SQ_RING); if (map == MAP_FAILED) { perror("mmap"); return 1; } /* We have at least one page. Let's COW it. */ *map = 0; pause(); return 0; } <--- C reproducer ---> On a system with 16 GiB RAM and swap configured: # ./iouring & # memhog 16G # killall iouring [ 301.552930] ------------[ cut here ]------------ [ 301.553285] WARNING: CPU: 7 PID: 1402 at arch/x86/mm/pat/memtype.c:1060 untrack_pfn+0xf4/0x100 [ 301.553989] Modules linked in: binfmt_misc nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_g [ 301.558232] CPU: 7 PID: 1402 Comm: iouring Not tainted 6.7.5-100.fc38.x86_64 #1 [ 301.558772] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebu4 [ 301.559569] RIP: 0010:untrack_pfn+0xf4/0x100 [ 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 [ 301.561189] RSP: 0018:ffffba2c0377fab8 EFLAGS: 00010282 [ 301.561590] RAX: 00000000ffffffea RBX: ffff9208c8ce9cc0 RCX: 000000010455e047 [ 301.562105] RDX: 07fffffff0eb1e0a RSI: 0000000000000000 RDI: ffff9208c391d200 [ 301.562628] RBP: 0000000000000000 R08: ffffba2c0377fab8 R09: 0000000000000000 [ 301.563145] R10: ffff9208d2292d50 R11: 0000000000000002 R12: 00007fea890e0000 [ 301.563669] R13: 0000000000000000 R14: ffffba2c0377fc08 R15: 0000000000000000 [ 301.564186] FS: 0000000000000000(0000) GS:ffff920c2fbc0000(0000) knlGS:0000000000000000 [ 301.564773] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 301.565197] CR2: 00007fea88ee8a20 CR3: 00000001033a8000 CR4: 0000000000750ef0 [ 301.565725] PKRU: 55555554 [ 301.565944] Call Trace: [ 301.566148] <TASK> [ 301.566325] ? untrack_pfn+0xf4/0x100 [ 301.566618] ? __warn+0x81/0x130 [ 301.566876] ? untrack_pfn+0xf4/0x100 [ 3 ---truncated---
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/04c35ab3bdae7fefbd7c7a7355f29fa03a035221
- https://git.kernel.org/stable/c/04c35ab3bdae7fefbd7c7a7355f29fa03a035221
- https://git.kernel.org/stable/c/09e6bb53217bf388a0d2fd7fb21e74ab9dffc173
- https://git.kernel.org/stable/c/1341e4b32e1fb1b0acd002ccd56f07bd32f2abc6
- https://git.kernel.org/stable/c/51b7841f3fe84606ec0bd8da859d22e05e5419ec
- https://git.kernel.org/stable/c/7cfee26d1950250b14c5cb0a37b142f3fcc6396a
- https://git.kernel.org/stable/c/97e93367e82752e475a33839a80b33bdbef1209f
- https://git.kernel.org/stable/c/c2b2430b48f3c9eaccd2c3d2ad75bb540d4952f4
- https://git.kernel.org/stable/c/f18681daaec9665a15c5e7e0f591aad5d0ac622b
- https://ubuntu.com/security/CVE-2024-35877
- https://ubuntu.com/security/notices/USN-6893-1
- https://ubuntu.com/security/notices/USN-6893-2
- https://ubuntu.com/security/notices/USN-6893-3
- https://ubuntu.com/security/notices/USN-6896-1
- https://ubuntu.com/security/notices/USN-6896-2
- https://ubuntu.com/security/notices/USN-6896-3
- https://ubuntu.com/security/notices/USN-6896-4
- https://ubuntu.com/security/notices/USN-6896-5
- https://ubuntu.com/security/notices/USN-6898-1
- https://ubuntu.com/security/notices/USN-6898-2
- https://ubuntu.com/security/notices/USN-6898-3
- https://ubuntu.com/security/notices/USN-6898-4
- https://ubuntu.com/security/notices/USN-6917-1
- https://ubuntu.com/security/notices/USN-6918-1
- https://ubuntu.com/security/notices/USN-6919-1
- https://ubuntu.com/security/notices/USN-6927-1
- https://ubuntu.com/security/notices/USN-7019-1
- https://ubuntu.com/security/notices/USN-7121-1
- https://ubuntu.com/security/notices/USN-7121-2
- https://ubuntu.com/security/notices/USN-7121-3
- https://ubuntu.com/security/notices/USN-7148-1
- https://www.cve.org/CVERecord?id=CVE-2024-35877