FAILED: patch "[PATCH] sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl()" failed to apply to 6.12-stable tree

FAILED: patch "[PATCH] sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl()" failed to apply to 6.12-stable tree

[gregkh]

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 9360dfe4cbd62ff1eb8217b815964931523b75b3
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025031614-broiler-overgrown-4bd4@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 9360dfe4cbd62ff1eb8217b815964931523b75b3 Mon Sep 17 00:00:00 2001
From: Andrea Righi <arighi@nvidia.com>
Date: Mon, 3 Mar 2025 18:51:59 +0100
Subject: [PATCH] sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl()

If a BPF scheduler provides an invalid CPU (outside the nr_cpu_ids
range) as prev_cpu to scx_bpf_select_cpu_dfl() it can cause a kernel
crash.

To prevent this, validate prev_cpu in scx_bpf_select_cpu_dfl() and
trigger an scx error if an invalid CPU is specified.

Fixes: f0e1a0643a59b ("sched_ext: Implement BPF extensible scheduler class")
Cc: stable@vger.kernel.org # v6.12+
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 0f1da199cfc7..7b9dfee858e7 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -6422,6 +6422,9 @@ static bool check_builtin_idle_enabled(void)
 __bpf_kfunc s32 scx_bpf_select_cpu_dfl(struct task_struct *p, s32 prev_cpu,
 				       u64 wake_flags, bool *is_idle)
 {
+	if (!ops_cpu_valid(prev_cpu, NULL))
+		goto prev_cpu;
+
 	if (!check_builtin_idle_enabled())
 		goto prev_cpu;
 

[PATCH 6.12.y] sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl()

[Andrea Righi]

If a BPF scheduler provides an invalid CPU (outside the nr_cpu_ids
range) as prev_cpu to scx_bpf_select_cpu_dfl() it can cause a kernel
crash.

To prevent this, validate prev_cpu in scx_bpf_select_cpu_dfl() and
trigger an scx error if an invalid CPU is specified.

Fixes: f0e1a0643a59b ("sched_ext: Implement BPF extensible scheduler class")
Cc: stable@vger.kernel.org # v6.12+
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
(cherry picked from commit 9360dfe4cbd62ff1eb8217b815964931523b75b3)
---
 kernel/sched/ext.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 325fd5b9d4715..e5cab54dfdd14 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -6052,6 +6052,9 @@ __bpf_kfunc_start_defs();
 __bpf_kfunc s32 scx_bpf_select_cpu_dfl(struct task_struct *p, s32 prev_cpu,
 				       u64 wake_flags, bool *is_idle)
 {
+	if (!ops_cpu_valid(prev_cpu, NULL))
+		goto prev_cpu;
+
 	if (!static_branch_likely(&scx_builtin_idle_enabled)) {
 		scx_ops_error("built-in idle tracking is disabled");
 		goto prev_cpu;
-- 
2.48.1

Re: [PATCH 6.12.y] sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl()

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

Summary of potential issues:
⚠️ Found matching upstream commit but patch is missing proper reference to it
ℹ️ Patch is missing in 6.13.y (ignore if backport was sent)
⚠️ Commit missing in all newer stable branches

Found matching upstream commit: 9360dfe4cbd62ff1eb8217b815964931523b75b3

Status in newer kernel trees:
6.13.y | Not found

Note: The patch differs from the upstream commit:
---
1:  9360dfe4cbd62 < -:  ------------- sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl()
-:  ------------- > 1:  a3b16615d84cc sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl()
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.12.y       |  Success    |  Success   |