{"cve":"CVE-2022-50344","nvd":{"published":"2025-09-16T17:15:34.070","modified":"2026-06-17T05:23:16.823","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix null-ptr-deref in ext4_write_info\n\nI caught a null-ptr-deref bug as follows:\n==================================================================\nKASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]\nCPU: 1 PID: 1589 Comm: umount Not tainted 5.10.0-02219-dirty #339\nRIP: 0010:ext4_write_info+0x53/0x1b0\n[...]\nCall Trace:\n dquot_writeback_dquots+0x341/0x9a0\n ext4_sync_fs+0x19e/0x800\n __sync_filesystem+0x83/0x100\n sync_filesystem+0x89/0xf0\n generic_shutdown_super+0x79/0x3e0\n kill_block_super+0xa1/0x110\n deactivate_locked_super+0xac/0x130\n deactivate_super+0xb6/0xd0\n cleanup_mnt+0x289/0x400\n __cleanup_mnt+0x16/0x20\n task_work_run+0x11c/0x1c0\n exit_to_user_mode_prepare+0x203/0x210\n syscall_exit_to_user_mode+0x5b/0x3a0\n do_syscall_64+0x59/0x70\n entry_SYSCALL_64_after_hwframe+0x44/0xa9\n ==================================================================\n\nAbove issue may happen as follows:\n-------------------------------------\nexit_to_user_mode_prepare\n task_work_run\n  __cleanup_mnt\n   cleanup_mnt\n    deactivate_super\n     deactivate_locked_super\n      kill_block_super\n       generic_shutdown_super\n        shrink_dcache_for_umount\n         dentry = sb->s_root\n         sb->s_root = NULL              <--- Here set NULL\n        sync_filesystem\n         __sync_filesystem\n          sb->s_op->sync_fs > ext4_sync_fs\n           dquot_writeback_dquots\n            sb->dq_op->write_info > ext4_write_info\n             ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2)\n              d_inode(sb->s_root)\n               s_root->d_inode          <--- Null pointer dereference\n\nTo solve this problem, we use ext4_journal_start_sb directly\nto avoid s_root being used.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":["CWE-476"],"references":["https://git.kernel.org/stable/c/3638aa1c7d87c0ca0aef23cf58cae2c48e7daca4","https://git.kernel.org/stable/c/4a657319cfabd6199fd0b7b65bbebf6ded7a11c1","https://git.kernel.org/stable/c/533c60a0b97cee5daab376933f486207e6680fb7","https://git.kernel.org/stable/c/947264e00c46de19a016fd81218118c708fed2f3","https://git.kernel.org/stable/c/bb420e8afc854d2a1caaa23a0c129839acfb7888"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:10:08.713834912+00:00"},"epss":{"cve":"CVE-2022-50344","score":0.00163,"percentile":0.05518,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}