[PATCH] cgroup: Avoid compiler warnings with no subsystems
flat view
STALE1868d
From: Kees Cook <hidden>
Date: 2021-08-27 03:47:51
Also in:
linux-hardening, lkml
Subsystem:
control group (cgroup), the rest · Maintainers:
Tejun Heo, Johannes Weiner, Michal Koutný, Linus Torvalds
As done before in commit cb4a31675270 ("cgroup: use bitmask to filter
for_each_subsys"), avoid compiler warnings for the pathological case of
having no subsystems (i.e. CGROUP_SUBSYS_COUNT == 0). This condition is
hit for the arm multi_v7_defconfig config under -Wzero-length-bounds:
In file included from ./arch/arm/include/generated/asm/rwonce.h:1,
from include/linux/compiler.h:264,
from include/uapi/linux/swab.h:6,
from include/linux/swab.h:5,
from arch/arm/include/asm/opcodes.h:86,
from arch/arm/include/asm/bug.h:7,
from include/linux/bug.h:5,
from include/linux/thread_info.h:13,
from include/asm-generic/current.h:5,
from ./arch/arm/include/generated/asm/current.h:1,
from include/linux/sched.h:12,
from include/linux/cgroup.h:12,
from kernel/cgroup/cgroup-internal.h:5,
from kernel/cgroup/cgroup.c:31:
kernel/cgroup/cgroup.c: In function 'of_css':
kernel/cgroup/cgroup.c:651:42: warning: array subscript '<unknown>' is outside the bounds of an
interior zero-length array 'struct cgroup_subsys_state *[0]' [-Wzero-length-bounds]
651 | return rcu_dereference_raw(cgrp->subsys[cft->ss->id]);
Reported-by: Stephen Rothwell <redacted>
Cc: Tejun Heo <redacted>
Cc: Zefan Li <redacted>
Cc: Johannes Weiner <redacted>
Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Signed-off-by: Kees Cook <redacted>
---
kernel/cgroup/cgroup.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index d0725c1a8db5..d23100878002 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c@@ -472,7 +472,7 @@ 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 (CGROUP_SUBSYS_COUNT && ss) return rcu_dereference_check(cgrp->subsys[ss->id], lockdep_is_held(&cgroup_mutex)); else
@@ -550,6 +550,9 @@ struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp, { struct cgroup_subsys_state *css; + if (!CGROUP_SUBSYS_COUNT) + return NULL; + do { css = cgroup_css(cgrp, ss);
@@ -577,6 +580,9 @@ struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgrp, { struct cgroup_subsys_state *css; + if (!CGROUP_SUBSYS_COUNT) + return NULL; + rcu_read_lock(); do {
@@ -647,7 +653,7 @@ 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 (CGROUP_SUBSYS_COUNT && cft->ss) return rcu_dereference_raw(cgrp->subsys[cft->ss->id]); else return &cgrp->self;
@@ -2372,7 +2378,7 @@ struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset, struct css_set *cset = tset->cur_cset; struct task_struct *task = tset->cur_task; - while (&cset->mg_node != tset->csets) { + while (CGROUP_SUBSYS_COUNT && &cset->mg_node != tset->csets) { if (!task) task = list_first_entry(&cset->mg_tasks, struct task_struct, cg_list);
@@ -4643,7 +4649,7 @@ void css_task_iter_start(struct cgroup_subsys_state *css, unsigned int flags, it->ss = css->ss; it->flags = flags; - if (it->ss) + if (CGROUP_SUBSYS_COUNT && it->ss) it->cset_pos = &css->cgroup->e_csets[css->ss->id]; else it->cset_pos = &css->cgroup->cset_links;
--
2.30.2