ghsa-37qc-prgq-xwcm
Vulnerability from github
Published
2024-07-12 15:31
Modified
2024-08-29 15:30
Severity ?
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Details

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

ax25: Fix refcount imbalance on inbound connections

When releasing a socket in ax25_release(), we call netdev_put() to decrease the refcount on the associated ax.25 device. However, the execution path for accepting an incoming connection never calls netdev_hold(). This imbalance leads to refcount errors, and ultimately to kernel crashes.

A typical call trace for the above situation will start with one of the following errors:

refcount_t: decrement hit 0; leaking memory.
refcount_t: underflow; use-after-free.

And will then have a trace like:

Call Trace:
<TASK>
? show_regs+0x64/0x70
? __warn+0x83/0x120
? refcount_warn_saturate+0xb2/0x100
? report_bug+0x158/0x190
? prb_read_valid+0x20/0x30
? handle_bug+0x3e/0x70
? exc_invalid_op+0x1c/0x70
? asm_exc_invalid_op+0x1f/0x30
? refcount_warn_saturate+0xb2/0x100
? refcount_warn_saturate+0xb2/0x100
ax25_release+0x2ad/0x360
__sock_release+0x35/0xa0
sock_close+0x19/0x20
[...]

On reboot (or any attempt to remove the interface), the kernel gets stuck in an infinite loop:

unregister_netdevice: waiting for ax0 to become free. Usage count = 0

This patch corrects these issues by ensuring that we call netdev_hold() and ax25_dev_hold() for new connections in ax25_accept(). This makes the logic leading to ax25_accept() match the logic for ax25_bind(): in both cases we increment the refcount, which is ultimately decremented in ax25_release().

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{
   affected: [],
   aliases: [
      "CVE-2024-40910",
   ],
   database_specific: {
      cwe_ids: [],
      github_reviewed: false,
      github_reviewed_at: null,
      nvd_published_at: "2024-07-12T13:15:14Z",
      severity: "MODERATE",
   },
   details: "In the Linux kernel, the following vulnerability has been resolved:\n\nax25: Fix refcount imbalance on inbound connections\n\nWhen releasing a socket in ax25_release(), we call netdev_put() to\ndecrease the refcount on the associated ax.25 device. However, the\nexecution path for accepting an incoming connection never calls\nnetdev_hold(). This imbalance leads to refcount errors, and ultimately\nto kernel crashes.\n\nA typical call trace for the above situation will start with one of the\nfollowing errors:\n\n    refcount_t: decrement hit 0; leaking memory.\n    refcount_t: underflow; use-after-free.\n\nAnd will then have a trace like:\n\n    Call Trace:\n    <TASK>\n    ? show_regs+0x64/0x70\n    ? __warn+0x83/0x120\n    ? refcount_warn_saturate+0xb2/0x100\n    ? report_bug+0x158/0x190\n    ? prb_read_valid+0x20/0x30\n    ? handle_bug+0x3e/0x70\n    ? exc_invalid_op+0x1c/0x70\n    ? asm_exc_invalid_op+0x1f/0x30\n    ? refcount_warn_saturate+0xb2/0x100\n    ? refcount_warn_saturate+0xb2/0x100\n    ax25_release+0x2ad/0x360\n    __sock_release+0x35/0xa0\n    sock_close+0x19/0x20\n    [...]\n\nOn reboot (or any attempt to remove the interface), the kernel gets\nstuck in an infinite loop:\n\n    unregister_netdevice: waiting for ax0 to become free. Usage count = 0\n\nThis patch corrects these issues by ensuring that we call netdev_hold()\nand ax25_dev_hold() for new connections in ax25_accept(). This makes the\nlogic leading to ax25_accept() match the logic for ax25_bind(): in both\ncases we increment the refcount, which is ultimately decremented in\nax25_release().",
   id: "GHSA-37qc-prgq-xwcm",
   modified: "2024-08-29T15:30:31Z",
   published: "2024-07-12T15:31:27Z",
   references: [
      {
         type: "ADVISORY",
         url: "https://nvd.nist.gov/vuln/detail/CVE-2024-40910",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/3c34fb0bd4a4237592c5ecb5b2e2531900c55774",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/52100fd74ad07b53a4666feafff1cd11436362d3",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/a723a6c8d4831cc8e2c7b0c9f3f0c010d4671964",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/f4df9d6c8d4e4c818252b0419c2165d66eabd4eb",
      },
   ],
   schema_version: "1.4.0",
   severity: [
      {
         score: "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
         type: "CVSS_V3",
      },
   ],
}


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