CVE-2024-26935 scsi: core: Fix unremoved procfs host directory regression

2024-05-0105:17:31

Linux

www.cve.org

linux kernel

vulnerability

scsi

regression

procfs

module loading

usb

device

error

usb mass storage

warning

fix

error path.

7.7 High

AI Score

Confidence

High

0.0004 Low

EPSS

Percentile

13.2%

JSON

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.

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "drivers/scsi/hosts.c"
    ],
    "versions": [
      {
        "version": "88c3d3bb6469",
        "lessThan": "0053f15d50d5",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "68c665bb1850",
        "lessThan": "5c2386ba80e7",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "2a764d55e938",
        "lessThan": "cea234bb214b",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "7e0ae8667fcd",
        "lessThan": "3678cf67ff71",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "be03df3d4bfe",
        "lessThan": "d4c34782b6d7",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "be03df3d4bfe",
        "lessThan": "e293c773c13b",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "be03df3d4bfe",
        "lessThan": "f4ff08fab66e",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "be03df3d4bfe",
        "lessThan": "f23a4d6e0757",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "drivers/scsi/hosts.c"
    ],
    "versions": [
      {
        "version": "6.3",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "6.3",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.4.274",
        "lessThanOrEqual": "5.4.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.10.215",
        "lessThanOrEqual": "5.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.15.154",
        "lessThanOrEqual": "5.15.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.1.84",
        "lessThanOrEqual": "6.1.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.6.24",
        "lessThanOrEqual": "6.6.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.7.12",
        "lessThanOrEqual": "6.7.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.8.3",
        "lessThanOrEqual": "6.8.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.9",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]