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cgroup: Avoid compiler warnings with no subsystems
As done before in commit cb4a316752
("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 <sfr@canb.auug.org.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zefan Li <lizefan.x@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: cgroups@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
parent
9f72daf7ed
commit
d20d30ebb1
1 changed files with 20 additions and 6 deletions
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@ -67,6 +67,14 @@
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/* let's not notify more than 100 times per second */
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#define CGROUP_FILE_NOTIFY_MIN_INTV DIV_ROUND_UP(HZ, 100)
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/*
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* To avoid confusing the compiler (and generating warnings) with code
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* that attempts to access what would be a 0-element array (i.e. sized
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* to a potentially empty array when CGROUP_SUBSYS_COUNT == 0), this
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* constant expression can be added.
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*/
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#define CGROUP_HAS_SUBSYS_CONFIG (CGROUP_SUBSYS_COUNT > 0)
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/*
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* cgroup_mutex is the master lock. Any modification to cgroup or its
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* hierarchy must be performed while holding it.
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@ -248,7 +256,7 @@ static int cgroup_addrm_files(struct cgroup_subsys_state *css,
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*/
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bool cgroup_ssid_enabled(int ssid)
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{
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if (CGROUP_SUBSYS_COUNT == 0)
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if (!CGROUP_HAS_SUBSYS_CONFIG)
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return false;
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return static_key_enabled(cgroup_subsys_enabled_key[ssid]);
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@ -472,7 +480,7 @@ static u16 cgroup_ss_mask(struct cgroup *cgrp)
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static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
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struct cgroup_subsys *ss)
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{
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if (ss)
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if (CGROUP_HAS_SUBSYS_CONFIG && ss)
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return rcu_dereference_check(cgrp->subsys[ss->id],
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lockdep_is_held(&cgroup_mutex));
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else
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@ -550,6 +558,9 @@ struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp,
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{
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struct cgroup_subsys_state *css;
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if (!CGROUP_HAS_SUBSYS_CONFIG)
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return NULL;
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do {
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css = cgroup_css(cgrp, ss);
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@ -577,6 +588,9 @@ struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgrp,
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{
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struct cgroup_subsys_state *css;
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if (!CGROUP_HAS_SUBSYS_CONFIG)
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return NULL;
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rcu_read_lock();
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do {
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@ -647,7 +661,7 @@ struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)
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* the matching css from the cgroup's subsys table is guaranteed to
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* be and stay valid until the enclosing operation is complete.
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*/
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if (cft->ss)
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if (CGROUP_HAS_SUBSYS_CONFIG && cft->ss)
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return rcu_dereference_raw(cgrp->subsys[cft->ss->id]);
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else
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return &cgrp->self;
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@ -695,7 +709,7 @@ EXPORT_SYMBOL_GPL(of_css);
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*/
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#define do_each_subsys_mask(ss, ssid, ss_mask) do { \
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unsigned long __ss_mask = (ss_mask); \
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if (!CGROUP_SUBSYS_COUNT) { /* to avoid spurious gcc warning */ \
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if (!CGROUP_HAS_SUBSYS_CONFIG) { \
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(ssid) = 0; \
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break; \
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} \
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@ -2372,7 +2386,7 @@ struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset,
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struct css_set *cset = tset->cur_cset;
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struct task_struct *task = tset->cur_task;
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while (&cset->mg_node != tset->csets) {
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while (CGROUP_HAS_SUBSYS_CONFIG && &cset->mg_node != tset->csets) {
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if (!task)
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task = list_first_entry(&cset->mg_tasks,
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struct task_struct, cg_list);
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@ -4643,7 +4657,7 @@ void css_task_iter_start(struct cgroup_subsys_state *css, unsigned int flags,
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it->ss = css->ss;
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it->flags = flags;
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if (it->ss)
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if (CGROUP_HAS_SUBSYS_CONFIG && it->ss)
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it->cset_pos = &css->cgroup->e_csets[css->ss->id];
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else
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it->cset_pos = &css->cgroup->cset_links;
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