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-rw-r--r--include/linux/cgroup.h14
-rw-r--r--kernel/cgroup.c35
2 files changed, 49 insertions, 0 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 88a734edccb..f5379455bb5 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -205,6 +205,13 @@ struct cftype {
* subsystem, followed by a period */
char name[MAX_CFTYPE_NAME];
int private;
+
+ /*
+ * If non-zero, defines the maximum length of string that can
+ * be passed to write_string; defaults to 64
+ */
+ size_t max_write_len;
+
int (*open)(struct inode *inode, struct file *file);
ssize_t (*read)(struct cgroup *cgrp, struct cftype *cft,
struct file *file,
@@ -249,6 +256,13 @@ struct cftype {
int (*write_s64)(struct cgroup *cgrp, struct cftype *cft, s64 val);
/*
+ * write_string() is passed a nul-terminated kernelspace
+ * buffer of maximum length determined by max_write_len.
+ * Returns 0 or -ve error code.
+ */
+ int (*write_string)(struct cgroup *cgrp, struct cftype *cft,
+ const char *buffer);
+ /*
* trigger() callback can be used to get some kick from the
* userspace, when the actual string written is not important
* at all. The private field can be used to determine the
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 70d083c6fb6..3a99cc2df86 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1363,6 +1363,39 @@ static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
return retval;
}
+static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft,
+ struct file *file,
+ const char __user *userbuf,
+ size_t nbytes, loff_t *unused_ppos)
+{
+ char local_buffer[64];
+ int retval = 0;
+ size_t max_bytes = cft->max_write_len;
+ char *buffer = local_buffer;
+
+ if (!max_bytes)
+ max_bytes = sizeof(local_buffer) - 1;
+ if (nbytes >= max_bytes)
+ return -E2BIG;
+ /* Allocate a dynamic buffer if we need one */
+ if (nbytes >= sizeof(local_buffer)) {
+ buffer = kmalloc(nbytes + 1, GFP_KERNEL);
+ if (buffer == NULL)
+ return -ENOMEM;
+ }
+ if (nbytes && copy_from_user(buffer, userbuf, nbytes))
+ return -EFAULT;
+
+ buffer[nbytes] = 0; /* nul-terminate */
+ strstrip(buffer);
+ retval = cft->write_string(cgrp, cft, buffer);
+ if (!retval)
+ retval = nbytes;
+ if (buffer != local_buffer)
+ kfree(buffer);
+ return retval;
+}
+
static ssize_t cgroup_common_file_write(struct cgroup *cgrp,
struct cftype *cft,
struct file *file,
@@ -1440,6 +1473,8 @@ static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
return cft->write(cgrp, cft, file, buf, nbytes, ppos);
if (cft->write_u64 || cft->write_s64)
return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
+ if (cft->write_string)
+ return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
if (cft->trigger) {
int ret = cft->trigger(cgrp, (unsigned int)cft->private);
return ret ? ret : nbytes;