From: Arnd Bergmann <arnd@kernel.org>
To: linux-kernel@vger.kernel.org, Martin Sebor <msebor@gcc.gnu.org>,
Tejun Heo <tj@kernel.org>, Zefan Li <lizefan.x@bytedance.com>,
Johannes Weiner <hannes@cmpxchg.org>
Cc: "Arnd Bergmann" <arnd@arndb.de>,
x86@kernel.org, "Ning Sun" <ning.sun@intel.com>,
"Jani Nikula" <jani.nikula@linux.intel.com>,
"Kalle Valo" <kvalo@codeaurora.org>,
"Simon Kelley" <simon@thekelleys.org.uk>,
"James Smart" <james.smart@broadcom.com>,
"James E.J. Bottomley" <jejb@linux.ibm.com>,
"Anders Larsen" <al@alarsen.net>,
"Serge Hallyn" <serge@hallyn.com>,
"Imre Deak" <imre.deak@intel.com>,
linux-arm-kernel@lists.infradead.org,
tboot-devel@lists.sourceforge.net,
intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
ath11k@lists.infradead.org, linux-wireless@vger.kernel.org,
netdev@vger.kernel.org, linux-scsi@vger.kernel.org,
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"Roman Gushchin" <guro@fb.com>,
"Christian Brauner" <christian.brauner@ubuntu.com>,
"Alexei Starovoitov" <ast@kernel.org>,
"Andrii Nakryiko" <andriin@fb.com>, "Odin Ugedal" <odin@uged.al>,
"Cong Wang" <xiyou.wangcong@gmail.com>,
"Michal Koutný" <mkoutny@suse.com>,
"Bhaskar Chowdhury" <unixbhaskar@gmail.com>
Subject: [PATCH 06/11] cgroup: fix -Wzero-length-bounds warnings
Date: Mon, 22 Mar 2021 17:02:44 +0100 [thread overview]
Message-ID: <20210322160253.4032422-7-arnd@kernel.org> (raw)
In-Reply-To: <20210322160253.4032422-1-arnd@kernel.org>
From: Arnd Bergmann <arnd@arndb.de>
When cgroups are enabled, but every single subsystem is turned off,
CGROUP_SUBSYS_COUNT is zero, and the cgrp->subsys[] array has no
members.
gcc-11 points out that this leads to an invalid access in any function
that might access this array:
kernel/cgroup/cgroup.c: In function 'cgroup_addrm_files':
kernel/cgroup/cgroup.c:460:58: warning: array subscript '<unknown>' is outside the bounds of an interior zero-length array 'struct cgroup_subsys_state *[0]' [-Wzero-length-bounds]
kernel/cgroup/cgroup.c:460:24: note: in expansion of macro 'rcu_dereference_check'
460 | return rcu_dereference_check(cgrp->subsys[ss->id],
| ^~~~~~~~~~~~~~~~~~~~~
In file included from include/linux/cgroup.h:28,
from kernel/cgroup/cgroup-internal.h:5,
from kernel/cgroup/cgroup.c:31:
include/linux/cgroup-defs.h:422:43: note: while referencing 'subsys'
422 | struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT];
I'm not sure what is expected to happen for such a configuration,
presumably these functions are never calls in that case. Adding a
sanity check in each function we get the warning for manages to shut
up the warnings and do nothing instead.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
I'm grouping this together with the -Wstringop-overread warnings,
since the underlying logic in gcc seems to be the same.
---
kernel/cgroup/cgroup.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 9153b20e5cc6..3477f1dc7872 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -456,7 +456,7 @@ static u16 cgroup_ss_mask(struct cgroup *cgrp)
static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
struct cgroup_subsys *ss)
{
- if (ss)
+ if (ss && (CGROUP_SUBSYS_COUNT > 0))
return rcu_dereference_check(cgrp->subsys[ss->id],
lockdep_is_held(&cgroup_mutex));
else
@@ -534,6 +534,9 @@ struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp,
{
struct cgroup_subsys_state *css;
+ if (CGROUP_SUBSYS_COUNT == 0)
+ return NULL;
+
do {
css = cgroup_css(cgrp, ss);
@@ -561,6 +564,9 @@ struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgrp,
{
struct cgroup_subsys_state *css;
+ if (CGROUP_SUBSYS_COUNT == 0)
+ return NULL;
+
rcu_read_lock();
do {
@@ -630,7 +636,7 @@ struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)
* the matching css from the cgroup's subsys table is guaranteed to
* be and stay valid until the enclosing operation is complete.
*/
- if (cft->ss)
+ if (cft->ss && CGROUP_SUBSYS_COUNT > 0)
return rcu_dereference_raw(cgrp->subsys[cft->ss->id]);
else
return &cgrp->self;
@@ -2343,6 +2349,9 @@ struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset,
struct css_set *cset = tset->cur_cset;
struct task_struct *task = tset->cur_task;
+ if (CGROUP_SUBSYS_COUNT == 0)
+ return NULL;
+
while (&cset->mg_node != tset->csets) {
if (!task)
task = list_first_entry(&cset->mg_tasks,
@@ -4523,7 +4532,7 @@ void css_task_iter_start(struct cgroup_subsys_state *css, unsigned int flags,
it->ss = css->ss;
it->flags = flags;
- if (it->ss)
+ if (it->ss && CGROUP_SUBSYS_COUNT > 0)
it->cset_pos = &css->cgroup->e_csets[css->ss->id];
else
it->cset_pos = &css->cgroup->cset_links;
--
2.29.2
next prev parent reply other threads:[~2021-03-22 16:05 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-22 16:02 [PATCH 00/11] treewide: address gcc-11 -Wstringop-overread warnings Arnd Bergmann
2021-03-22 16:02 ` [PATCH 01/11] x86: compressed: avoid gcc-11 -Wstringop-overread warning Arnd Bergmann
2021-03-22 16:02 ` [PATCH 02/11] x86: tboot: avoid Wstringop-overread-warning Arnd Bergmann
2021-03-22 20:29 ` Ingo Molnar
2021-03-22 21:39 ` Arnd Bergmann
2021-03-22 22:07 ` Martin Sebor
2021-03-22 22:49 ` Arnd Bergmann
2021-03-22 23:13 ` Ingo Molnar
2021-03-24 9:11 ` David Laight
2021-03-24 10:39 ` David Laight
2021-03-22 16:02 ` [PATCH 03/11] security: commoncap: fix -Wstringop-overread warning Arnd Bergmann
2021-03-22 16:31 ` Christian Brauner
2021-03-24 20:50 ` James Morris
2021-03-22 16:02 ` [PATCH 04/11] ath11: Wstringop-overread warning Arnd Bergmann
2021-09-28 9:04 ` Kalle Valo
2021-03-22 16:02 ` [PATCH 05/11] qnx: avoid -Wstringop-overread warning Arnd Bergmann
2021-03-22 16:02 ` Arnd Bergmann [this message]
2021-03-30 8:41 ` [PATCH 06/11] cgroup: fix -Wzero-length-bounds warnings Michal Koutný
2021-03-30 9:00 ` Arnd Bergmann
2021-03-30 14:44 ` Michal Koutný
2021-03-22 16:02 ` [PATCH 07/11] ARM: sharpsl_param: work around -Wstringop-overread warning Arnd Bergmann
2021-03-22 16:02 ` [PATCH 08/11] atmel: avoid gcc -Wstringop-overflow warning Arnd Bergmann
2021-03-22 16:02 ` [PATCH 09/11] scsi: lpfc: fix gcc -Wstringop-overread warning Arnd Bergmann
2021-03-22 16:02 ` [PATCH 10/11] drm/i915: avoid stringop-overread warning on pri_latency Arnd Bergmann
2021-03-24 15:30 ` Jani Nikula
2021-03-24 17:22 ` Ville Syrjälä
2021-03-22 16:02 ` [PATCH 11/11] [RFC] drm/i915/dp: fix array overflow warning Arnd Bergmann
2021-03-25 8:05 ` Jani Nikula
2021-03-25 9:53 ` Arnd Bergmann
2021-03-25 14:49 ` Martin Sebor
2021-03-30 10:56 ` Hans de Goede
2021-04-06 4:53 ` [PATCH 00/11] treewide: address gcc-11 -Wstringop-overread warnings Martin K. Petersen
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