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

2024-05-0105:17:31

Linux

github.com

linux kernel

vulnerability

scsi core

6.6 Medium

AI Score

Confidence

Low

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

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