From: =?utf-8?b?TWljaGFsIEtvdXRuw70gPG1rb3V0bnlAc3VzZS5jb20+?=

Date: Fri, 26 Aug 2022 18:52:37 +0200

Subject: cgroup: Homogenize cgroup_get_from_id() return value

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Git-commit: fa7e439cf90ba23ea473d0b7d85efd02ae6ccf94

Patch-mainline: v6.1-rc1

References: bsc#1205650

Cgroup id is user provided datum hence extend its return domain to

include possible error reason (similar to cgroup_get_from_fd()).

This change also fixes commit d4ccaf58a847 ("bpf: Introduce cgroup

iter") that would use NULL instead of proper error handling in

d4ccaf58a847 ("bpf: Introduce cgroup iter").

Additionally, neither of: fc_appid_store, bpf_iter_attach_cgroup,

mem_cgroup_get_from_ino (callers of cgroup_get_from_fd) is built without

CONFIG_CGROUPS (depends via CONFIG_BLK_CGROUP, direct, transitive

CONFIG_MEMCG respectively) transitive, so drop the singular definition

not needed with !CONFIG_CGROUPS.

Fixes: d4ccaf58a847 ("bpf: Introduce cgroup iter")

Signed-off-by: Michal Koutný <mkoutny@suse.com>

Signed-off-by: Tejun Heo <tj@kernel.org>

[mkoutny: drop mem_cgroup_get_from_ino() hunk]

---

 block/blk-cgroup-fc-appid.c |    4 ++--

 include/linux/cgroup.h      |    5 -----

 kernel/cgroup/cgroup.c      |    4 ++--

 3 files changed, 4 insertions(+), 9 deletions(-)

--- a/block/blk-cgroup-fc-appid.c

+++ b/block/blk-cgroup-fc-appid.c

@@ -19,8 +19,8 @@ int blkcg_set_fc_appid(char *app_id, u64

 		return -EINVAL;

 	cgrp = cgroup_get_from_id(cgrp_id);

-	if (!cgrp)

-		return -ENOENT;

+	if (IS_ERR(cgrp))

+		return PTR_ERR(cgrp);

 	css = cgroup_get_e_css(cgrp, &io_cgrp_subsys);

 	if (!css) {

 		ret = -ENOENT;

--- a/include/linux/cgroup.h

+++ b/include/linux/cgroup.h

@@ -751,11 +751,6 @@ static inline bool task_under_cgroup_hie

 static inline void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)

 {}

-

-static inline struct cgroup *cgroup_get_from_id(u64 id)

-{

-	return NULL;

-}

 #endif /* !CONFIG_CGROUPS */

 #ifdef CONFIG_CGROUPS

--- a/kernel/cgroup/cgroup.c

+++ b/kernel/cgroup/cgroup.c

@@ -6002,7 +6002,7 @@ void cgroup_path_from_kernfs_id(u64 id,

 /*

  * cgroup_get_from_id : get the cgroup associated with cgroup id

  * @id: cgroup id

- * On success return the cgrp, on failure return NULL

+ * On success return the cgrp or ERR_PTR on failure

  * Only cgroups within current task's cgroup NS are valid.

  */

 struct cgroup *cgroup_get_from_id(u64 id)

@@ -6038,7 +6038,7 @@ put:

 		cgrp = NULL;

 	}

 out:

-	return cgrp;

+	return cgrp ?: ERR_PTR(-ENOENT);

 }

 EXPORT_SYMBOL_GPL(cgroup_get_from_id);