CVE-2026-80671: perf sched: Fix register_pid() overflow, strcpy, and BUG_ON

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

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

perf sched: Fix register_pid() overflow, strcpy, and BUG_ON

register_pid() has several issues when processing untrusted perf.data:

1. Integer overflow: (pid + 1) * sizeof(struct task_desc *) can wrap
   to a small value on 32-bit systems when pid is large (e.g.
   0x40000000), causing realloc to return a tiny buffer followed by
   out-of-bounds writes in the initialization loop.

2. Heap buffer overflow: strcpy(task->comm, comm) copies the
   untrusted comm string into a fixed 20-byte COMM_LEN buffer with
   no length check.

3. BUG_ON on allocation failure: perf.data is untrusted input, so
   allocation failures should be handled gracefully rather than
   killing the process.

4. Realloc of sched->tasks assigned directly back, leaking the old
   pointer on failure; nr_tasks incremented before the realloc,
   leaving corrupted state on failure.

Cap pid at PID_MAX_LIMIT (4194304, matching the kernel's maximum
on 64-bit), replace strcpy with strlcpy, guard against NULL comm,
replace BUG_ON with NULL returns using safe realloc patterns, and
add NULL checks in callers that dereference the result.

The Linux kernel CVE team has assigned CVE-2026-80671 to this issue.


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

	Issue introduced in 2.6.32 with commit ec156764d424dd67283c2cd5e9f6f1b8388364ac and fixed in 6.18.40 with commit 652cea73b7b7b7c622a2be670e44e3c499c6d49f
	Issue introduced in 2.6.32 with commit ec156764d424dd67283c2cd5e9f6f1b8388364ac and fixed in 7.1.5 with commit 5ea1dcc9418c4e06ce29ed5170596f497ba86872
	Issue introduced in 2.6.32 with commit ec156764d424dd67283c2cd5e9f6f1b8388364ac and fixed in 7.2 with commit 5949d339f5ec98752d56dcd4e36f619a59d513a5

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-2026-80671
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:
	tools/perf/builtin-sched.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/652cea73b7b7b7c622a2be670e44e3c499c6d49f
	https://git.kernel.org/stable/c/5ea1dcc9418c4e06ce29ed5170596f497ba86872
	https://git.kernel.org/stable/c/5949d339f5ec98752d56dcd4e36f619a59d513a5