linux-cve-announce - CVE-2025-68208: bpf: account for current allocated stack depth in widen_imprecise

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Message-ID: <2025121633-CVE-2025-68208-d2fc@gregkh>
Date: Tue, 16 Dec 2025 14:54:37 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-68208: bpf: account for current allocated stack depth in widen_imprecise_scalars()

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

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

bpf: account for current allocated stack depth in widen_imprecise_scalars()

The usage pattern for widen_imprecise_scalars() looks as follows:

    prev_st = find_prev_entry(env, ...);
    queued_st = push_stack(...);
    widen_imprecise_scalars(env, prev_st, queued_st);

Where prev_st is an ancestor of the queued_st in the explored states
tree. This ancestor is not guaranteed to have same allocated stack
depth as queued_st. E.g. in the following case:

    def main():
      for i in 1..2:
        foo(i)        // same callsite, differnt param

    def foo(i):
      if i == 1:
        use 128 bytes of stack
      iterator based loop

Here, for a second 'foo' call prev_st->allocated_stack is 128,
while queued_st->allocated_stack is much smaller.
widen_imprecise_scalars() needs to take this into account and avoid
accessing bpf_verifier_state->frame[*]->stack out of bounds.

The Linux kernel CVE team has assigned CVE-2025-68208 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.6.15 with commit ab470fefce2837e66b771c60858118d50bb5bb10 and fixed in 6.6.117 with commit 64b12dca2b0abcb5fc0542887d18b926ea5cf711
	Issue introduced in 6.7 with commit 2793a8b015f7f1caadb9bce9c63dc659f7522676 and fixed in 6.12.59 with commit 9944c7938cd5b3f37b0afec0481c7c015e4f1c58
	Issue introduced in 6.7 with commit 2793a8b015f7f1caadb9bce9c63dc659f7522676 and fixed in 6.17.9 with commit 57e04e2ff56e32f923154f0f7bc476fcb596ffe7
	Issue introduced in 6.7 with commit 2793a8b015f7f1caadb9bce9c63dc659f7522676 and fixed in 6.18 with commit b0c8e6d3d866b6a7f73877f71968dbffd27b7785

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-68208
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	kernel/bpf/verifier.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/64b12dca2b0abcb5fc0542887d18b926ea5cf711
	https://git.kernel.org/stable/c/9944c7938cd5b3f37b0afec0481c7c015e4f1c58
	https://git.kernel.org/stable/c/57e04e2ff56e32f923154f0f7bc476fcb596ffe7
	https://git.kernel.org/stable/c/b0c8e6d3d866b6a7f73877f71968dbffd27b7785