fkie_cve-2021-47118
Vulnerability from fkie_nvd
Published
2024-03-15 21:15
Modified
2024-11-21 06:35
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: pid: take a reference when initializing `cad_pid` During boot, kernel_init_freeable() initializes `cad_pid` to the init task's struct pid. Later on, we may change `cad_pid` via a sysctl, and when this happens proc_do_cad_pid() will increment the refcount on the new pid via get_pid(), and will decrement the refcount on the old pid via put_pid(). As we never called get_pid() when we initialized `cad_pid`, we decrement a reference we never incremented, can therefore free the init task's struct pid early. As there can be dangling references to the struct pid, we can later encounter a use-after-free (e.g. when delivering signals). This was spotted when fuzzing v5.13-rc3 with Syzkaller, but seems to have been around since the conversion of `cad_pid` to struct pid in commit 9ec52099e4b8 ("[PATCH] replace cad_pid by a struct pid") from the pre-KASAN stone age of v2.6.19. Fix this by getting a reference to the init task's struct pid when we assign it to `cad_pid`. Full KASAN splat below. ================================================================== BUG: KASAN: use-after-free in ns_of_pid include/linux/pid.h:153 [inline] BUG: KASAN: use-after-free in task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509 Read of size 4 at addr ffff23794dda0004 by task syz-executor.0/273 CPU: 1 PID: 273 Comm: syz-executor.0 Not tainted 5.12.0-00001-g9aef892b2d15 #1 Hardware name: linux,dummy-virt (DT) Call trace: ns_of_pid include/linux/pid.h:153 [inline] task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509 do_notify_parent+0x308/0xe60 kernel/signal.c:1950 exit_notify kernel/exit.c:682 [inline] do_exit+0x2334/0x2bd0 kernel/exit.c:845 do_group_exit+0x108/0x2c8 kernel/exit.c:922 get_signal+0x4e4/0x2a88 kernel/signal.c:2781 do_signal arch/arm64/kernel/signal.c:882 [inline] do_notify_resume+0x300/0x970 arch/arm64/kernel/signal.c:936 work_pending+0xc/0x2dc Allocated by task 0: slab_post_alloc_hook+0x50/0x5c0 mm/slab.h:516 slab_alloc_node mm/slub.c:2907 [inline] slab_alloc mm/slub.c:2915 [inline] kmem_cache_alloc+0x1f4/0x4c0 mm/slub.c:2920 alloc_pid+0xdc/0xc00 kernel/pid.c:180 copy_process+0x2794/0x5e18 kernel/fork.c:2129 kernel_clone+0x194/0x13c8 kernel/fork.c:2500 kernel_thread+0xd4/0x110 kernel/fork.c:2552 rest_init+0x44/0x4a0 init/main.c:687 arch_call_rest_init+0x1c/0x28 start_kernel+0x520/0x554 init/main.c:1064 0x0 Freed by task 270: slab_free_hook mm/slub.c:1562 [inline] slab_free_freelist_hook+0x98/0x260 mm/slub.c:1600 slab_free mm/slub.c:3161 [inline] kmem_cache_free+0x224/0x8e0 mm/slub.c:3177 put_pid.part.4+0xe0/0x1a8 kernel/pid.c:114 put_pid+0x30/0x48 kernel/pid.c:109 proc_do_cad_pid+0x190/0x1b0 kernel/sysctl.c:1401 proc_sys_call_handler+0x338/0x4b0 fs/proc/proc_sysctl.c:591 proc_sys_write+0x34/0x48 fs/proc/proc_sysctl.c:617 call_write_iter include/linux/fs.h:1977 [inline] new_sync_write+0x3ac/0x510 fs/read_write.c:518 vfs_write fs/read_write.c:605 [inline] vfs_write+0x9c4/0x1018 fs/read_write.c:585 ksys_write+0x124/0x240 fs/read_write.c:658 __do_sys_write fs/read_write.c:670 [inline] __se_sys_write fs/read_write.c:667 [inline] __arm64_sys_write+0x78/0xb0 fs/read_write.c:667 __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline] invoke_syscall arch/arm64/kernel/syscall.c:49 [inline] el0_svc_common.constprop.1+0x16c/0x388 arch/arm64/kernel/syscall.c:129 do_el0_svc+0xf8/0x150 arch/arm64/kernel/syscall.c:168 el0_svc+0x28/0x38 arch/arm64/kernel/entry-common.c:416 el0_sync_handler+0x134/0x180 arch/arm64/kernel/entry-common.c:432 el0_sync+0x154/0x180 arch/arm64/kernel/entry.S:701 The buggy address belongs to the object at ffff23794dda0000 which belongs to the cache pid of size 224 The buggy address is located 4 bytes inside of 224-byte region [ff ---truncated---
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/0711f0d7050b9e07c44bc159bbc64ac0a1022c7f
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2cd6eedfa6344f5ef5c3dac3aee57a39b5b46dff
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/4dbd8808a591b49b717862e6e0081bcf14a87788
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7178be006d495ffb741c329012da289b62dddfe6
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/764c2e892d1fe895392aff62fb353fdce43bb529
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b8ff869f20152fbe66b6c2e2715d26a2f9897cca
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d106f05432e60f9f62d456ef017687f5c73cb414
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f86c80515a8a3703e0ca2e56deb50fc2879c5ea4
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/0711f0d7050b9e07c44bc159bbc64ac0a1022c7f
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/2cd6eedfa6344f5ef5c3dac3aee57a39b5b46dff
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/4dbd8808a591b49b717862e6e0081bcf14a87788
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/7178be006d495ffb741c329012da289b62dddfe6
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/764c2e892d1fe895392aff62fb353fdce43bb529
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/b8ff869f20152fbe66b6c2e2715d26a2f9897cca
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/d106f05432e60f9f62d456ef017687f5c73cb414
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/f86c80515a8a3703e0ca2e56deb50fc2879c5ea4
Impacted products
Vendor Product Version


To clipboard 

{
  "cveTags": [],
  "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\u0027s 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\u0027s 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\u0027s 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---"
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: pid: toma una referencia al inicializar `cad_pid` Durante el arranque, kernel_init_freeable() inicializa `cad_pid` en la estructura pid de la tarea de inicio. M\u00e1s adelante, podemos cambiar `cad_pid` mediante un sysctl, y cuando esto suceda, proc_do_cad_pid() incrementar\u00e1 el recuento en el nuevo pid mediante get_pid(), y disminuir\u00e1 el recuento en el pid antiguo mediante put_pid(). Como nunca llamamos a get_pid() cuando inicializamos `cad_pid`, disminuimos una referencia que nunca incrementamos, por lo que podemos liberar la estructura pid de la tarea de inicio antes. Como puede haber referencias pendientes a la estructura pid, m\u00e1s adelante podemos encontrarnos con un use-after-free (por ejemplo, al entregar se\u00f1ales). Esto se detect\u00f3 al fusionar v5.13-rc3 con Syzkaller, pero parece haber existido desde la conversi\u00f3n de `cad_pid` a struct pid en el commit 9ec52099e4b8 (\"[PATCH] reemplaza cad_pid por una estructura pid\") del pre-KASAN edad de piedra de v2.6.19. Solucione este problema obteniendo una referencia a la estructura pid de la tarea de inicio cuando la asignamos a `cad_pid`. S\u00edmbolo completo de KASAN a continuaci\u00f3n. ==================================================== ================ ERROR: KASAN: use-after-free en ns_of_pid include/linux/pid.h:153 [en l\u00ednea] ERROR: KASAN: use-after-free en task_active_pid_ns +0xc0/0xc8 kernel/pid.c:509 Lectura de tama\u00f1o 4 en addr ffff23794dda0004 por tarea syz-executor.0/273 CPU: 1 PID: 273 Comm: syz-executor.0 No contaminado 5.12.0-00001-g9aef892b2d15 # 1 Nombre del hardware: linux,dummy-virt (DT) Rastreo de llamadas: ns_of_pid include/linux/pid.h:153 [en l\u00ednea] task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509 do_notify_parent+0x308/0xe60 kernel/signal.c :1950 exit_notify kernel/exit.c:682 [en l\u00ednea] do_exit+0x2334/0x2bd0 kernel/exit.c:845 do_group_exit+0x108/0x2c8 kernel/exit.c:922 get_signal+0x4e4/0x2a88 kernel/signal.c:2781 do_signal arch/arm64/kernel/signal.c:882 [en l\u00ednea] do_notify_resume+0x300/0x970 arch/arm64/kernel/signal.c:936 work_pending+0xc/0x2dc Asignado por tarea 0: slab_post_alloc_hook+0x50/0x5c0 mm/slab.h :516 slab_alloc_node mm/slub.c:2907 [en l\u00ednea] slab_alloc mm/slub.c:2915 [en l\u00ednea] kmem_cache_alloc+0x1f4/0x4c0 mm/slub.c:2920 alloc_pid+0xdc/0xc00 kernel/pid.c:180 copy_process+ 0x2794/0x5e18 kernel/fork.c:2129 kernel_clone+0x194/0x13c8 kernel/fork.c:2500 kernel_thread+0xd4/0x110 kernel/fork.c:2552 rest_init+0x44/0x4a0 init/main.c:687 arch_call_rest_init+0x1c/ 0x28 start_kernel+0x520/0x554 init/main.c:1064 0x0 Liberado por la tarea 270: slab_free_hook mm/slub.c:1562 [en l\u00ednea] slab_free_freelist_hook+0x98/0x260 mm/slub.c:1600 slab_free mm/slub.c:3161 [en l\u00ednea] kmem_cache_free+0x224/0x8e0 mm/slub.c:3177 put_pid.part.4+0xe0/0x1a8 kernel/pid.c:114 put_pid+0x30/0x48 kernel/pid.c:109 proc_do_cad_pid+0x190/0x1b0 kernel/ sysctl.c:1401 proc_sys_call_handler+0x338/0x4b0 fs/proc/proc_sysctl.c:591 proc_sys_write+0x34/0x48 fs/proc/proc_sysctl.c:617 call_write_iter include/linux/fs.h:1977 [en l\u00ednea] new_sync_write+0x3ac/ 0x510 fs/read_write.c:518 vfs_write fs/read_write.c:605 [en l\u00ednea] vfs_write+0x9c4/0x1018 fs/read_write.c:585 ksys_write+0x124/0x240 fs/read_write.c:658 __do_sys_write fs/read_write.c: 670 [en l\u00ednea] __se_sys_write fs/read_write.c:667 [en l\u00ednea] __arm64_sys_write+0x78/0xb0 fs/read_write.c:667 __invoke_syscall arch/arm64/kernel/syscall.c:37 [en l\u00ednea] invoke_syscall arch/arm64/kernel/syscall .c:49 [en l\u00ednea] el0_svc_common.constprop.1+0x16c/0x388 arch/arm64/kernel/syscall.c:129 do_el0_svc+0xf8/0x150 arch/arm64/kernel/syscall.c:168 el0_svc+0x28/0x38 arch/ arm64/kernel/entry-common.c:416 el0_sync_handler+0x134/0x180 arch/arm64/kernel/entry-common.c:432 el0_sync+0x154/0x180 arch/arm64/kernel/entry.S:701 La direcci\u00f3n del error pertenece a el objeto en ffff23794dda0000 que pertenece al pid de cach\u00e9 de tama\u00f1o 224.---truncado---"
    }
  ],
  "id": "CVE-2021-47118",
  "lastModified": "2024-11-21T06:35:25.993",
  "metrics": {},
  "published": "2024-03-15T21:15:06.943",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/0711f0d7050b9e07c44bc159bbc64ac0a1022c7f"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/2cd6eedfa6344f5ef5c3dac3aee57a39b5b46dff"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/4dbd8808a591b49b717862e6e0081bcf14a87788"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/7178be006d495ffb741c329012da289b62dddfe6"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/764c2e892d1fe895392aff62fb353fdce43bb529"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/b8ff869f20152fbe66b6c2e2715d26a2f9897cca"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d106f05432e60f9f62d456ef017687f5c73cb414"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f86c80515a8a3703e0ca2e56deb50fc2879c5ea4"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "https://git.kernel.org/stable/c/0711f0d7050b9e07c44bc159bbc64ac0a1022c7f"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "https://git.kernel.org/stable/c/2cd6eedfa6344f5ef5c3dac3aee57a39b5b46dff"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "https://git.kernel.org/stable/c/4dbd8808a591b49b717862e6e0081bcf14a87788"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "https://git.kernel.org/stable/c/7178be006d495ffb741c329012da289b62dddfe6"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "https://git.kernel.org/stable/c/764c2e892d1fe895392aff62fb353fdce43bb529"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "https://git.kernel.org/stable/c/b8ff869f20152fbe66b6c2e2715d26a2f9897cca"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "https://git.kernel.org/stable/c/d106f05432e60f9f62d456ef017687f5c73cb414"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "https://git.kernel.org/stable/c/f86c80515a8a3703e0ca2e56deb50fc2879c5ea4"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}


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