ghsa-hxgr-6xc2-q9mv
Vulnerability from github
Published
2024-05-01 06:31
Modified
2024-06-25 21:31
Details

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

scsi: core: Fix unremoved procfs host directory regression

Commit fc663711b944 ("scsi: core: Remove the /proc/scsi/${proc_name} directory earlier") fixed a bug related to modules loading/unloading, by adding a call to scsi_proc_hostdir_rm() on scsi_remove_host(). But that led to a potential duplicate call to the hostdir_rm() routine, since it's also called from scsi_host_dev_release(). That triggered a regression report, which was then fixed by commit be03df3d4bfe ("scsi: core: Fix a procfs host directory removal regression"). The fix just dropped the hostdir_rm() call from dev_release().

But it happens that this proc directory is created on scsi_host_alloc(), and that function "pairs" with scsi_host_dev_release(), while scsi_remove_host() pairs with scsi_add_host(). In other words, it seems the reason for removing the proc directory on dev_release() was meant to cover cases in which a SCSI host structure was allocated, but the call to scsi_add_host() didn't happen. And that pattern happens to exist in some error paths, for example.

Syzkaller causes that by using USB raw gadget device, error'ing on usb-storage driver, at usb_stor_probe2(). By checking that path, we can see that the BadDevice label leads to a scsi_host_put() after a SCSI host allocation, but there's no call to scsi_add_host() in such path. That leads to messages like this in dmesg (and a leak of the SCSI host proc structure):

usb-storage 4-1:87.51: USB Mass Storage device detected proc_dir_entry 'scsi/usb-storage' already registered WARNING: CPU: 1 PID: 3519 at fs/proc/generic.c:377 proc_register+0x347/0x4e0 fs/proc/generic.c:376

The proper fix seems to still call scsi_proc_hostdir_rm() on dev_release(), but guard that with the state check for SHOST_CREATED; there is even a comment in scsi_host_dev_release() detailing that: such conditional is meant for cases where the SCSI host was allocated but there was no calls to {add,remove}_host(), like the usb-storage case.

This is what we propose here and with that, the error path of usb-storage does not trigger the warning anymore.

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{
  "affected": [],
  "aliases": [
    "CVE-2024-26935"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-05-01T06:15:08Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nscsi: core: Fix unremoved procfs host directory regression\n\nCommit fc663711b944 (\"scsi: core: Remove the /proc/scsi/${proc_name}\ndirectory earlier\") fixed a bug related to modules loading/unloading, by\nadding a call to scsi_proc_hostdir_rm() on scsi_remove_host(). But that led\nto a potential duplicate call to the hostdir_rm() routine, since it\u0027s also\ncalled from scsi_host_dev_release(). That triggered a regression report,\nwhich was then fixed by commit be03df3d4bfe (\"scsi: core: Fix a procfs host\ndirectory removal regression\"). The fix just dropped the hostdir_rm() call\nfrom dev_release().\n\nBut it happens that this proc directory is created on scsi_host_alloc(),\nand that function \"pairs\" with scsi_host_dev_release(), while\nscsi_remove_host() pairs with scsi_add_host(). In other words, it seems the\nreason for removing the proc directory on dev_release() was meant to cover\ncases in which a SCSI host structure was allocated, but the call to\nscsi_add_host() didn\u0027t happen. And that pattern happens to exist in some\nerror paths, for example.\n\nSyzkaller causes that by using USB raw gadget device, error\u0027ing on\nusb-storage driver, at usb_stor_probe2(). By checking that path, we can see\nthat the BadDevice label leads to a scsi_host_put() after a SCSI host\nallocation, but there\u0027s no call to scsi_add_host() in such path. That leads\nto messages like this in dmesg (and a leak of the SCSI host proc\nstructure):\n\nusb-storage 4-1:87.51: USB Mass Storage device detected\nproc_dir_entry \u0027scsi/usb-storage\u0027 already registered\nWARNING: CPU: 1 PID: 3519 at fs/proc/generic.c:377 proc_register+0x347/0x4e0 fs/proc/generic.c:376\n\nThe proper fix seems to still call scsi_proc_hostdir_rm() on dev_release(),\nbut guard that with the state check for SHOST_CREATED; there is even a\ncomment in scsi_host_dev_release() detailing that: such conditional is\nmeant for cases where the SCSI host was allocated but there was no calls to\n{add,remove}_host(), like the usb-storage case.\n\nThis is what we propose here and with that, the error path of usb-storage\ndoes not trigger the warning anymore.",
  "id": "GHSA-hxgr-6xc2-q9mv",
  "modified": "2024-06-25T21:31:12Z",
  "published": "2024-05-01T06:31:41Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-26935"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0053f15d50d50c9312d8ab9c11e2e405812dfcac"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3678cf67ff7136db1dd3bf63c361650db5d92889"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5c2386ba80e779a92ec3bb64ccadbedd88f779b1"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/cea234bb214b17d004dfdccce4491e6ff57c96ee"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d4c34782b6d7b1e68d18d9549451b19433bd4c6c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e293c773c13b830cdc251f155df2254981abc320"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f23a4d6e07570826fe95023ca1aa96a011fa9f84"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f4ff08fab66eb5c0b97e1a24edac052fb40bf5d7"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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