linux-kernel - [PATCH 5.5 072/151] cgroup: fix psi

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Message-Id: <20200317103331.602367219@linuxfoundation.org>
Date:   Tue, 17 Mar 2020 11:54:42 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Qian Cai <cai@....pw>,
        Johannes Weiner <hannes@...xchg.org>, Tejun Heo <tj@...nel.org>
Subject: [PATCH 5.5 072/151] cgroup: fix psi_show() crash on 32bit ino archs

From: Qian Cai <cai@....pw>

commit 190ecb190a9cd8c0599d8499b901e3c32e87966a upstream.

Similar to the commit d7495343228f ("cgroup: fix incorrect
WARN_ON_ONCE() in cgroup_setup_root()"), cgroup_id(root_cgrp) does not
equal to 1 on 32bit ino archs which triggers all sorts of issues with
psi_show() on s390x. For example,

 BUG: KASAN: slab-out-of-bounds in collect_percpu_times+0x2d0/
 Read of size 4 at addr 000000001e0ce000 by task read_all/3667
 collect_percpu_times+0x2d0/0x798
 psi_show+0x7c/0x2a8
 seq_read+0x2ac/0x830
 vfs_read+0x92/0x150
 ksys_read+0xe2/0x188
 system_call+0xd8/0x2b4

Fix it by using cgroup_ino().

Fixes: 743210386c03 ("cgroup: use cgrp->kn->id as the cgroup ID")
Signed-off-by: Qian Cai <cai@....pw>
Acked-by: Johannes Weiner <hannes@...xchg.org>
Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: stable@...r.kernel.org # v5.5
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/cgroup/cgroup.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -3547,21 +3547,21 @@ static int cpu_stat_show(struct seq_file
 static int cgroup_io_pressure_show(struct seq_file *seq, void *v)
 {
 	struct cgroup *cgrp = seq_css(seq)->cgroup;
-	struct psi_group *psi = cgroup_id(cgrp) == 1 ? &psi_system : &cgrp->psi;
+	struct psi_group *psi = cgroup_ino(cgrp) == 1 ? &psi_system : &cgrp->psi;
 
 	return psi_show(seq, psi, PSI_IO);
 }
 static int cgroup_memory_pressure_show(struct seq_file *seq, void *v)
 {
 	struct cgroup *cgrp = seq_css(seq)->cgroup;
-	struct psi_group *psi = cgroup_id(cgrp) == 1 ? &psi_system : &cgrp->psi;
+	struct psi_group *psi = cgroup_ino(cgrp) == 1 ? &psi_system : &cgrp->psi;
 
 	return psi_show(seq, psi, PSI_MEM);
 }
 static int cgroup_cpu_pressure_show(struct seq_file *seq, void *v)
 {
 	struct cgroup *cgrp = seq_css(seq)->cgroup;
-	struct psi_group *psi = cgroup_id(cgrp) == 1 ? &psi_system : &cgrp->psi;
+	struct psi_group *psi = cgroup_ino(cgrp) == 1 ? &psi_system : &cgrp->psi;
 
 	return psi_show(seq, psi, PSI_CPU);
 }