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workqueue: fix parse_affn_scope() prefix matching bug

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parse_affn_scope() uses strncasecmp() with the length of the candidate
name, which means it only checks if the input *starts with* a known
scope name.

Given that the upcoming diff will create "cache_shard" affinity scope,
writing "cache_shard" to a workqueue's affinity_scope sysfs attribute
always matches "cache" first, making it impossible to select
"cache_shard" via sysfs, so, this fix enable it to distinguish "cache"
and "cache_shard"

Fix by replacing the hand-rolled prefix matching loop with
sysfs_match_string(), which uses sysfs_streq() for exact matching
(modulo trailing newlines). Also add the missing const qualifier to
the wq_affn_names[] array declaration.

Note that sysfs_streq() is case-sensitive, unlike the previous
strncasecmp() approach. This is intentional and consistent with
how other sysfs attributes handle string matching in the kernel.

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Breno Leitao 2026-03-12 09:12:02 -07:00 committed by Tejun Heo
parent b39bf7f0fa
commit 1abaae9b38
1 changed files with 2 additions and 8 deletions
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10
kernel/workqueue.c
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@ -405,7 +405,7 @@ struct work_offq_data {
u32 flags;
};
static const char *wq_affn_names[WQ_AFFN_NR_TYPES] = {
static const char * const wq_affn_names[WQ_AFFN_NR_TYPES] = {
[WQ_AFFN_DFL] = "default",
[WQ_AFFN_CPU] = "cpu",
[WQ_AFFN_SMT] = "smt",
@ -7093,13 +7093,7 @@ int workqueue_unbound_housekeeping_update(const struct cpumask *hk)
static int parse_affn_scope(const char *val)
{
int i;
for (i = 0; i < ARRAY_SIZE(wq_affn_names); i++) {
if (!strncasecmp(val, wq_affn_names[i], strlen(wq_affn_names[i])))
return i;
}
return -EINVAL;
return sysfs_match_string(wq_affn_names, val);
}
static int wq_affn_dfl_set(const char *val, const struct kernel_param *kp)