ghsa-fhmx-7jhg-8h34
Vulnerability from github
Published
2024-11-19 18:31
Modified
2024-11-22 21:32
Severity ?
4.4 (Medium) - CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
Details

In the Linux kernel, the following vulnerability has been resolved:

io_uring/rw: fix missing NOWAIT check for O_DIRECT start write

When io_uring starts a write, it'll call kiocb_start_write() to bump the super block rwsem, preventing any freezes from happening while that write is in-flight. The freeze side will grab that rwsem for writing, excluding any new writers from happening and waiting for existing writes to finish. But io_uring unconditionally uses kiocb_start_write(), which will block if someone is currently attempting to freeze the mount point. This causes a deadlock where freeze is waiting for previous writes to complete, but the previous writes cannot complete, as the task that is supposed to complete them is blocked waiting on starting a new write. This results in the following stuck trace showing that dependency with the write blocked starting a new write:

task:fio state:D stack:0 pid:886 tgid:886 ppid:876 Call trace: __switch_to+0x1d8/0x348 __schedule+0x8e8/0x2248 schedule+0x110/0x3f0 percpu_rwsem_wait+0x1e8/0x3f8 __percpu_down_read+0xe8/0x500 io_write+0xbb8/0xff8 io_issue_sqe+0x10c/0x1020 io_submit_sqes+0x614/0x2110 __arm64_sys_io_uring_enter+0x524/0x1038 invoke_syscall+0x74/0x268 el0_svc_common.constprop.0+0x160/0x238 do_el0_svc+0x44/0x60 el0_svc+0x44/0xb0 el0t_64_sync_handler+0x118/0x128 el0t_64_sync+0x168/0x170 INFO: task fsfreeze:7364 blocked for more than 15 seconds. Not tainted 6.12.0-rc5-00063-g76aaf945701c #7963

with the attempting freezer stuck trying to grab the rwsem:

task:fsfreeze state:D stack:0 pid:7364 tgid:7364 ppid:995 Call trace: __switch_to+0x1d8/0x348 __schedule+0x8e8/0x2248 schedule+0x110/0x3f0 percpu_down_write+0x2b0/0x680 freeze_super+0x248/0x8a8 do_vfs_ioctl+0x149c/0x1b18 __arm64_sys_ioctl+0xd0/0x1a0 invoke_syscall+0x74/0x268 el0_svc_common.constprop.0+0x160/0x238 do_el0_svc+0x44/0x60 el0_svc+0x44/0xb0 el0t_64_sync_handler+0x118/0x128 el0t_64_sync+0x168/0x170

Fix this by having the io_uring side honor IOCB_NOWAIT, and only attempt a blocking grab of the super block rwsem if it isn't set. For normal issue where IOCB_NOWAIT would always be set, this returns -EAGAIN which will have io_uring core issue a blocking attempt of the write. That will in turn also get completions run, ensuring forward progress.

Since freezing requires CAP_SYS_ADMIN in the first place, this isn't something that can be triggered by a regular user.

Show details on source website

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{
  "affected": [],
  "aliases": [
    "CVE-2024-53052"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-667"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-11-19T18:15:25Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring/rw: fix missing NOWAIT check for O_DIRECT start write\n\nWhen io_uring starts a write, it\u0027ll call kiocb_start_write() to bump the\nsuper block rwsem, preventing any freezes from happening while that\nwrite is in-flight. The freeze side will grab that rwsem for writing,\nexcluding any new writers from happening and waiting for existing writes\nto finish. But io_uring unconditionally uses kiocb_start_write(), which\nwill block if someone is currently attempting to freeze the mount point.\nThis causes a deadlock where freeze is waiting for previous writes to\ncomplete, but the previous writes cannot complete, as the task that is\nsupposed to complete them is blocked waiting on starting a new write.\nThis results in the following stuck trace showing that dependency with\nthe write blocked starting a new write:\n\ntask:fio             state:D stack:0     pid:886   tgid:886   ppid:876\nCall trace:\n __switch_to+0x1d8/0x348\n __schedule+0x8e8/0x2248\n schedule+0x110/0x3f0\n percpu_rwsem_wait+0x1e8/0x3f8\n __percpu_down_read+0xe8/0x500\n io_write+0xbb8/0xff8\n io_issue_sqe+0x10c/0x1020\n io_submit_sqes+0x614/0x2110\n __arm64_sys_io_uring_enter+0x524/0x1038\n invoke_syscall+0x74/0x268\n el0_svc_common.constprop.0+0x160/0x238\n do_el0_svc+0x44/0x60\n el0_svc+0x44/0xb0\n el0t_64_sync_handler+0x118/0x128\n el0t_64_sync+0x168/0x170\nINFO: task fsfreeze:7364 blocked for more than 15 seconds.\n      Not tainted 6.12.0-rc5-00063-g76aaf945701c #7963\n\nwith the attempting freezer stuck trying to grab the rwsem:\n\ntask:fsfreeze        state:D stack:0     pid:7364  tgid:7364  ppid:995\nCall trace:\n __switch_to+0x1d8/0x348\n __schedule+0x8e8/0x2248\n schedule+0x110/0x3f0\n percpu_down_write+0x2b0/0x680\n freeze_super+0x248/0x8a8\n do_vfs_ioctl+0x149c/0x1b18\n __arm64_sys_ioctl+0xd0/0x1a0\n invoke_syscall+0x74/0x268\n el0_svc_common.constprop.0+0x160/0x238\n do_el0_svc+0x44/0x60\n el0_svc+0x44/0xb0\n el0t_64_sync_handler+0x118/0x128\n el0t_64_sync+0x168/0x170\n\nFix this by having the io_uring side honor IOCB_NOWAIT, and only attempt a\nblocking grab of the super block rwsem if it isn\u0027t set. For normal issue\nwhere IOCB_NOWAIT would always be set, this returns -EAGAIN which will\nhave io_uring core issue a blocking attempt of the write. That will in\nturn also get completions run, ensuring forward progress.\n\nSince freezing requires CAP_SYS_ADMIN in the first place, this isn\u0027t\nsomething that can be triggered by a regular user.",
  "id": "GHSA-fhmx-7jhg-8h34",
  "modified": "2024-11-22T21:32:13Z",
  "published": "2024-11-19T18:31:06Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-53052"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/003d2996964c03dfd34860500428f4cdf1f5879e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1d60d74e852647255bd8e76f5a22dc42531e4389"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/26b8c48f369b7591f5679e0b90612f4862a32929"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/485d9232112b17f389b29497ff41b97b3189546b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4e24041ba86d50aaa4c792ae2c88ed01b3d96243"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9e8debb8e51354b201db494689198078ec2c1e75"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}


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