{"id":"DEBIAN-CVE-2021-47089","details":"In the Linux kernel, the following vulnerability has been resolved:  kfence: fix memory leak when cat kfence objects  Hulk robot reported a kmemleak problem:      unreferenced object 0xffff93d1d8cc02e8 (size 248):       comm \"cat\", pid 23327, jiffies 4624670141 (age 495992.217s)       hex dump (first 32 bytes):         00 40 85 19 d4 93 ff ff 00 10 00 00 00 00 00 00  .@..............         00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................       backtrace:          seq_open+0x2a/0x80          full_proxy_open+0x167/0x1e0          do_dentry_open+0x1e1/0x3a0          path_openat+0x961/0xa20          do_filp_open+0xae/0x120          do_sys_openat2+0x216/0x2f0          do_sys_open+0x57/0x80          do_syscall_64+0x33/0x40          entry_SYSCALL_64_after_hwframe+0x44/0xa9     unreferenced object 0xffff93d419854000 (size 4096):       comm \"cat\", pid 23327, jiffies 4624670141 (age 495992.217s)       hex dump (first 32 bytes):         6b 66 65 6e 63 65 2d 23 32 35 30 3a 20 30 78 30  kfence-#250: 0x0         30 30 30 30 30 30 30 37 35 34 62 64 61 31 32 2d  0000000754bda12-       backtrace:          seq_read_iter+0x313/0x440          seq_read+0x14b/0x1a0          full_proxy_read+0x56/0x80          vfs_read+0xa5/0x1b0          ksys_read+0xa0/0xf0          do_syscall_64+0x33/0x40          entry_SYSCALL_64_after_hwframe+0x44/0xa9  I find that we can easily reproduce this problem with the following commands:  \tcat /sys/kernel/debug/kfence/objects \techo scan \u003e /sys/kernel/debug/kmemleak \tcat /sys/kernel/debug/kmemleak  The leaked memory is allocated in the stack below:      do_syscall_64       do_sys_open         do_dentry_open           full_proxy_open             seq_open            ---\u003e alloc seq_file       vfs_read         full_proxy_read           seq_read             seq_read_iter               traverse          ---\u003e alloc seq_buf  And it should have been released in the following process:      do_syscall_64       syscall_exit_to_user_mode         exit_to_user_mode_prepare           task_work_run             ____fput               __fput                 full_proxy_release  ---\u003e free here  However, the release function corresponding to file_operations is not implemented in kfence.  As a result, a memory leak occurs.  Therefore, the solution to this problem is to implement the corresponding release function.","modified":"2026-09-01T20:04:36.693891800Z","published":"2024-03-04T18:15:07.560Z","upstream":["CVE-2021-47089"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2021-47089"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.15.15-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-47089.json"}},{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.15.15-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-47089.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.15.15-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-47089.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L"}]}