{"id":"CVE-2021-47089","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nkfence: fix memory leak when cat kfence objects\n\nHulk robot reported a kmemleak problem:\n\n    unreferenced object 0xffff93d1d8cc02e8 (size 248):\n      comm \"cat\", pid 23327, jiffies 4624670141 (age 495992.217s)\n      hex dump (first 32 bytes):\n        00 40 85 19 d4 93 ff ff 00 10 00 00 00 00 00 00  .@..............\n        00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................\n      backtrace:\n         seq_open+0x2a/0x80\n         full_proxy_open+0x167/0x1e0\n         do_dentry_open+0x1e1/0x3a0\n         path_openat+0x961/0xa20\n         do_filp_open+0xae/0x120\n         do_sys_openat2+0x216/0x2f0\n         do_sys_open+0x57/0x80\n         do_syscall_64+0x33/0x40\n         entry_SYSCALL_64_after_hwframe+0x44/0xa9\n    unreferenced object 0xffff93d419854000 (size 4096):\n      comm \"cat\", pid 23327, jiffies 4624670141 (age 495992.217s)\n      hex dump (first 32 bytes):\n        6b 66 65 6e 63 65 2d 23 32 35 30 3a 20 30 78 30  kfence-#250: 0x0\n        30 30 30 30 30 30 30 37 35 34 62 64 61 31 32 2d  0000000754bda12-\n      backtrace:\n         seq_read_iter+0x313/0x440\n         seq_read+0x14b/0x1a0\n         full_proxy_read+0x56/0x80\n         vfs_read+0xa5/0x1b0\n         ksys_read+0xa0/0xf0\n         do_syscall_64+0x33/0x40\n         entry_SYSCALL_64_after_hwframe+0x44/0xa9\n\nI find that we can easily reproduce this problem with the following\ncommands:\n\n\tcat /sys/kernel/debug/kfence/objects\n\techo scan \u003e /sys/kernel/debug/kmemleak\n\tcat /sys/kernel/debug/kmemleak\n\nThe leaked memory is allocated in the stack below:\n\n    do_syscall_64\n      do_sys_open\n        do_dentry_open\n          full_proxy_open\n            seq_open            ---\u003e alloc seq_file\n      vfs_read\n        full_proxy_read\n          seq_read\n            seq_read_iter\n              traverse          ---\u003e alloc seq_buf\n\nAnd it should have been released in the following process:\n\n    do_syscall_64\n      syscall_exit_to_user_mode\n        exit_to_user_mode_prepare\n          task_work_run\n            ____fput\n              __fput\n                full_proxy_release  ---\u003e free here\n\nHowever, the release function corresponding to file_operations is not\nimplemented in kfence.  As a result, a memory leak occurs.  Therefore,\nthe solution to this problem is to implement the corresponding release\nfunction.","modified":"2026-03-15T22:42:47.578816Z","published":"2024-03-04T18:15:07.560Z","related":["SUSE-SU-2024:2372-1","SUSE-SU-2024:2394-1","SUSE-SU-2024:2939-1"],"references":[{"type":"FIX","url":"https://git.kernel.org/stable/c/2f06c8293d27f6337f907042c602c9c953988c48"},{"type":"FIX","url":"https://git.kernel.org/stable/c/0129ab1f268b6cf88825eae819b9b84aa0a85634"}],"affected":[{"database_specific":{"unresolved_ranges":[{"events":[{"introduced":"5.12"},{"fixed":"5.15.12"}]},{"events":[{"introduced":"0"},{"last_affected":"5.16-rc1"}]},{"events":[{"introduced":"0"},{"last_affected":"5.16-rc2"}]},{"events":[{"introduced":"0"},{"last_affected":"5.16-rc3"}]},{"events":[{"introduced":"0"},{"last_affected":"5.16-rc4"}]},{"events":[{"introduced":"0"},{"last_affected":"5.16-rc5"}]},{"events":[{"introduced":"0"},{"last_affected":"5.16-rc6"}]}],"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-47089.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L"}]}