CVE-2024-26737

2024-04-0317:15:51

Linux

web.nvd.nist.gov

linux kernel

vulnerability

bpf racing issue

uaf

timer manipulation

AI Score

6.3

Confidence

Low

EPSS

Percentile

15.5%

JSON

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

bpf: Fix racing between bpf_timer_cancel_and_free and bpf_timer_cancel

The following race is possible between bpf_timer_cancel_and_free
and bpf_timer_cancel. It will lead a UAF on the timer->timer.

bpf_timer_cancel();
spin_lock();
t = timer->time;
spin_unlock();

				bpf_timer_cancel_and_free();
					spin_lock();
					t = timer-&gt;timer;
					timer-&gt;timer = NULL;
					spin_unlock();
					hrtimer_cancel(&t-&gt;timer);
					kfree(t);

/* UAF on t */
hrtimer_cancel(&t-&gt;timer);

In bpf_timer_cancel_and_free, this patch frees the timer->timer
after a rcu grace period. This requires a rcu_head addition
to the “struct bpf_hrtimer”. Another kfree(t) happens in bpf_timer_init,
this does not need a kfree_rcu because it is still under the
spin_lock and timer->timer has not been visible by others yet.

In bpf_timer_cancel, rcu_read_lock() is added because this helper
can be used in a non rcu critical section context (e.g. from
a sleepable bpf prog). Other timer->timer usages in helpers.c
have been audited, bpf_timer_cancel() is the only place where
timer->timer is used outside of the spin_lock.

Another solution considered is to mark a t->flag in bpf_timer_cancel
and clear it after hrtimer_cancel() is done. In bpf_timer_cancel_and_free,
it busy waits for the flag to be cleared before kfree(t). This patch
goes with a straight forward solution and frees timer->timer after
a rcu grace period.

Affected configurations

Vulners

Node

linuxlinux_kernelRange5.15–5.15.150

linuxlinux_kernelRange5.16.0–6.1.80

linuxlinux_kernelRange6.2.0–6.6.19

linuxlinux_kernelRange6.7.0–6.7.7

linuxlinux_kernelRange6.8.0≥

VendorProductVersionCPE
linuxlinux_kernel*cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

Vendor	Product	Version	CPE
linux	linux_kernel	*	cpe:2.3:o:linux:linux_kernel::::::::

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "kernel/bpf/helpers.c"
    ],
    "versions": [
      {
        "version": "b00628b1c7d5",
        "lessThan": "5268bb02107b",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "b00628b1c7d5",
        "lessThan": "addf5e297e6c",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "b00628b1c7d5",
        "lessThan": "8327ed12e8eb",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "b00628b1c7d5",
        "lessThan": "7d80a9e745fa",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "b00628b1c7d5",
        "lessThan": "0281b919e175",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "kernel/bpf/helpers.c"
    ],
    "versions": [
      {
        "version": "5.15",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "5.15",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.15.150",
        "lessThanOrEqual": "5.15.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.1.80",
        "lessThanOrEqual": "6.1.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.6.19",
        "lessThanOrEqual": "6.6.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.7.7",
        "lessThanOrEqual": "6.7.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.8",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]