3.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Tejun Heo <tj@xxxxxxxxxx>
commit e605b36575e896edd8161534550c9ea021b03bc0 upstream.
If a cgroup file implements either read_map() or read_seq_string(),
such file is served using seq_file by overriding file->f_op to
cgroup_seqfile_operations, which also overrides the release method to
single_release() from cgroup_file_release().
Because cgroup_file_open() didn't use to acquire any resources, this
used to be fine, but since f7d58818ba42 ("cgroup: pin
cgroup_subsys_state when opening a cgroupfs file"), cgroup_file_open()
pins the css (cgroup_subsys_state) which is put by
cgroup_file_release(). The patch forgot to update the release path
for seq_files and each open/release cycle leaks a css reference.
Fix it by updating cgroup_file_release() to also handle seq_files and
using it for seq_file release path too.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/cgroup.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -231,6 +231,7 @@ static void cgroup_destroy_css_killed(st
static int cgroup_destroy_locked(struct cgroup *cgrp);
static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
bool is_add);
+static int cgroup_file_release(struct inode *inode, struct file *file);
/**
* cgroup_css - obtain a cgroup's css for the specified subsystem
@@ -2471,7 +2472,7 @@ static const struct file_operations cgro
.read = seq_read,
.write = cgroup_file_write,
.llseek = seq_lseek,
- .release = single_release,
+ .release = cgroup_file_release,
};
static int cgroup_file_open(struct inode *inode, struct file *file)
@@ -2532,6 +2533,8 @@ static int cgroup_file_release(struct in
ret = cft->release(inode, file);
if (css->ss)
css_put(css);
+ if (file->f_op == &cgroup_seqfile_operations)
+ single_release(inode, file);
return ret;
}
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