{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2021-47118", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-03-04T18:12:48.838Z", "datePublished": "2024-03-15T20:14:25.116Z", "dateUpdated": "2026-05-11T13:48:23.853Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-05-11T13:48:23.853Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\npid: take a reference when initializing `cad_pid`\n\nDuring boot, kernel_init_freeable() initializes `cad_pid` to the init\ntask's struct pid. Later on, we may change `cad_pid` via a sysctl, and\nwhen this happens proc_do_cad_pid() will increment the refcount on the\nnew pid via get_pid(), and will decrement the refcount on the old pid\nvia put_pid(). As we never called get_pid() when we initialized\n`cad_pid`, we decrement a reference we never incremented, can therefore\nfree the init task's struct pid early. As there can be dangling\nreferences to the struct pid, we can later encounter a use-after-free\n(e.g. when delivering signals).\n\nThis was spotted when fuzzing v5.13-rc3 with Syzkaller, but seems to\nhave been around since the conversion of `cad_pid` to struct pid in\ncommit 9ec52099e4b8 (\"[PATCH] replace cad_pid by a struct pid\") from the\npre-KASAN stone age of v2.6.19.\n\nFix this by getting a reference to the init task's struct pid when we\nassign it to `cad_pid`.\n\nFull KASAN splat below.\n\n ==================================================================\n BUG: KASAN: use-after-free in ns_of_pid include/linux/pid.h:153 [inline]\n BUG: KASAN: use-after-free in task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509\n Read of size 4 at addr ffff23794dda0004 by task syz-executor.0/273\n\n CPU: 1 PID: 273 Comm: syz-executor.0 Not tainted 5.12.0-00001-g9aef892b2d15 #1\n Hardware name: linux,dummy-virt (DT)\n Call trace:\n ns_of_pid include/linux/pid.h:153 [inline]\n task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509\n do_notify_parent+0x308/0xe60 kernel/signal.c:1950\n exit_notify kernel/exit.c:682 [inline]\n do_exit+0x2334/0x2bd0 kernel/exit.c:845\n do_group_exit+0x108/0x2c8 kernel/exit.c:922\n get_signal+0x4e4/0x2a88 kernel/signal.c:2781\n do_signal arch/arm64/kernel/signal.c:882 [inline]\n do_notify_resume+0x300/0x970 arch/arm64/kernel/signal.c:936\n work_pending+0xc/0x2dc\n\n Allocated by task 0:\n slab_post_alloc_hook+0x50/0x5c0 mm/slab.h:516\n slab_alloc_node mm/slub.c:2907 [inline]\n slab_alloc mm/slub.c:2915 [inline]\n kmem_cache_alloc+0x1f4/0x4c0 mm/slub.c:2920\n alloc_pid+0xdc/0xc00 kernel/pid.c:180\n copy_process+0x2794/0x5e18 kernel/fork.c:2129\n kernel_clone+0x194/0x13c8 kernel/fork.c:2500\n kernel_thread+0xd4/0x110 kernel/fork.c:2552\n rest_init+0x44/0x4a0 init/main.c:687\n arch_call_rest_init+0x1c/0x28\n start_kernel+0x520/0x554 init/main.c:1064\n 0x0\n\n Freed by task 270:\n slab_free_hook mm/slub.c:1562 [inline]\n slab_free_freelist_hook+0x98/0x260 mm/slub.c:1600\n slab_free mm/slub.c:3161 [inline]\n kmem_cache_free+0x224/0x8e0 mm/slub.c:3177\n put_pid.part.4+0xe0/0x1a8 kernel/pid.c:114\n put_pid+0x30/0x48 kernel/pid.c:109\n proc_do_cad_pid+0x190/0x1b0 kernel/sysctl.c:1401\n proc_sys_call_handler+0x338/0x4b0 fs/proc/proc_sysctl.c:591\n proc_sys_write+0x34/0x48 fs/proc/proc_sysctl.c:617\n call_write_iter include/linux/fs.h:1977 [inline]\n new_sync_write+0x3ac/0x510 fs/read_write.c:518\n vfs_write fs/read_write.c:605 [inline]\n vfs_write+0x9c4/0x1018 fs/read_write.c:585\n ksys_write+0x124/0x240 fs/read_write.c:658\n __do_sys_write fs/read_write.c:670 [inline]\n __se_sys_write fs/read_write.c:667 [inline]\n __arm64_sys_write+0x78/0xb0 fs/read_write.c:667\n __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]\n invoke_syscall arch/arm64/kernel/syscall.c:49 [inline]\n el0_svc_common.constprop.1+0x16c/0x388 arch/arm64/kernel/syscall.c:129\n do_el0_svc+0xf8/0x150 arch/arm64/kernel/syscall.c:168\n el0_svc+0x28/0x38 arch/arm64/kernel/entry-common.c:416\n el0_sync_handler+0x134/0x180 arch/arm64/kernel/entry-common.c:432\n el0_sync+0x154/0x180 arch/arm64/kernel/entry.S:701\n\n The buggy address belongs to the object at ffff23794dda0000\n which belongs to the cache pid of size 224\n The buggy address is located 4 bytes inside of\n 224-byte region [ff\n---truncated---" } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "init/main.c" ], "versions": [ { "version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "lessThan": "764c2e892d1fe895392aff62fb353fdce43bb529", "status": "affected", "versionType": "git" }, { "version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "lessThan": "f86c80515a8a3703e0ca2e56deb50fc2879c5ea4", "status": "affected", "versionType": "git" }, { "version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "lessThan": "4dbd8808a591b49b717862e6e0081bcf14a87788", "status": "affected", "versionType": "git" }, { "version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "lessThan": "d106f05432e60f9f62d456ef017687f5c73cb414", "status": "affected", "versionType": "git" }, { "version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "lessThan": "2cd6eedfa6344f5ef5c3dac3aee57a39b5b46dff", "status": "affected", "versionType": "git" }, { "version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "lessThan": "7178be006d495ffb741c329012da289b62dddfe6", "status": "affected", "versionType": "git" }, { "version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "lessThan": "b8ff869f20152fbe66b6c2e2715d26a2f9897cca", "status": "affected", "versionType": "git" }, { "version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "lessThan": "0711f0d7050b9e07c44bc159bbc64ac0a1022c7f", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "init/main.c" ], "versions": [ { "version": "2.6.19", "status": "affected" }, { "version": "0", "lessThan": "2.6.19", "status": "unaffected", "versionType": "semver" }, { "version": "4.4.272", "lessThanOrEqual": "4.4.*", "status": "unaffected", "versionType": "semver" }, { "version": "4.9.272", "lessThanOrEqual": "4.9.*", "status": "unaffected", "versionType": "semver" }, { "version": "4.14.236", "lessThanOrEqual": "4.14.*", "status": "unaffected", "versionType": "semver" }, { "version": "4.19.194", "lessThanOrEqual": "4.19.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.4.125", "lessThanOrEqual": "5.4.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.43", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.12.10", "lessThanOrEqual": "5.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.13", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.19", "versionEndExcluding": "4.4.272" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.19", "versionEndExcluding": "4.9.272" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.19", "versionEndExcluding": "4.14.236" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.19", "versionEndExcluding": "4.19.194" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.19", "versionEndExcluding": "5.4.125" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.19", "versionEndExcluding": "5.10.43" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.19", "versionEndExcluding": "5.12.10" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.19", "versionEndExcluding": "5.13" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/764c2e892d1fe895392aff62fb353fdce43bb529" }, { "url": "https://git.kernel.org/stable/c/f86c80515a8a3703e0ca2e56deb50fc2879c5ea4" }, { "url": "https://git.kernel.org/stable/c/4dbd8808a591b49b717862e6e0081bcf14a87788" }, { "url": "https://git.kernel.org/stable/c/d106f05432e60f9f62d456ef017687f5c73cb414" }, { "url": "https://git.kernel.org/stable/c/2cd6eedfa6344f5ef5c3dac3aee57a39b5b46dff" }, { "url": "https://git.kernel.org/stable/c/7178be006d495ffb741c329012da289b62dddfe6" }, { "url": "https://git.kernel.org/stable/c/b8ff869f20152fbe66b6c2e2715d26a2f9897cca" }, { "url": "https://git.kernel.org/stable/c/0711f0d7050b9e07c44bc159bbc64ac0a1022c7f" } ], "title": "pid: take a reference when initializing `cad_pid`", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "providerMetadata": { "orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2024-08-04T05:24:39.826Z" }, "title": "CVE Program Container", "references": [ { "url": "https://git.kernel.org/stable/c/764c2e892d1fe895392aff62fb353fdce43bb529", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/f86c80515a8a3703e0ca2e56deb50fc2879c5ea4", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/4dbd8808a591b49b717862e6e0081bcf14a87788", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/d106f05432e60f9f62d456ef017687f5c73cb414", "tags": [ "x_transferred" ] }, { "url": 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