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Subject[PATCH 6/6] FS: proc, make limits writable
Date
Allow writing strings such as
Max core file size=0:unlimited
to /proc/<pid>/limits to change limits.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
---
fs/proc/base.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 76 insertions(+), 2 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index ea71cae..0d9e3e9 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -129,6 +129,8 @@ struct pid_entry {
NULL, &proc_single_file_operations, \
{ .proc_show = show } )

+static ssize_t proc_info_read(struct file * file, char __user * buf,
+ size_t count, loff_t *ppos);
/*
* Count the number of hardlinks for the pid_entry table, excluding the .
* and .. links.
@@ -522,6 +524,74 @@ static int proc_pid_limits(struct task_struct *task, char *buffer)
return count;
}

+static ssize_t limits_write(struct file *file, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
+ char str[32 + 1 + 16 + 1 + 16 + 1], *delim, *next;
+ struct rlimit new_rlimit;
+ unsigned int i;
+ int ret;
+
+ if (!task) {
+ count = -ESRCH;
+ goto out;
+ }
+ if (copy_from_user(str, buf, min(count, sizeof(str) - 1))) {
+ count = -EFAULT;
+ goto put_task;
+ }
+
+ str[min(count, sizeof(str) - 1)] = 0;
+
+ delim = strchr(str, '=');
+ if (!delim) {
+ count = -EINVAL;
+ goto put_task;
+ }
+ *delim++ = 0; /* for easy 'str' usage */
+ new_rlimit.rlim_cur = simple_strtoul(delim, &next, 0);
+ if (*next != ':') {
+ if (strncmp(delim, "unlimited:", 10)) {
+ count = -EINVAL;
+ goto put_task;
+ }
+ new_rlimit.rlim_cur = RLIM_INFINITY;
+ next = delim + 9; /* move to ':' */
+ }
+ delim = next + 1;
+ new_rlimit.rlim_max = simple_strtoul(delim, &next, 0);
+ if (*next != 0) {
+ if (strcmp(delim, "unlimited")) {
+ count = -EINVAL;
+ goto put_task;
+ }
+ new_rlimit.rlim_max = RLIM_INFINITY;
+ }
+
+ for (i = 0; i < RLIM_NLIMITS; i++)
+ if (!strcmp(str, lnames[i].name))
+ break;
+ if (i >= RLIM_NLIMITS) {
+ count = -EINVAL;
+ goto put_task;
+ }
+
+ ret = setrlimit(task, i, &new_rlimit);
+ if (ret)
+ count = ret;
+
+put_task:
+ put_task_struct(task);
+out:
+ return count;
+}
+
+static const struct file_operations proc_pid_limits_operations = {
+ .read = proc_info_read,
+ .write = limits_write,
+};
+
#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
static int proc_pid_syscall(struct task_struct *task, char *buffer)
{
@@ -2501,7 +2571,9 @@ static const struct pid_entry tgid_base_stuff[] = {
INF("auxv", S_IRUSR, proc_pid_auxv),
ONE("status", S_IRUGO, proc_pid_status),
ONE("personality", S_IRUSR, proc_pid_personality),
- INF("limits", S_IRUSR, proc_pid_limits),
+ NOD("limits", S_IFREG|S_IRUSR|S_IWUSR, NULL,
+ &proc_pid_limits_operations,
+ { .proc_read = proc_pid_limits }),
#ifdef CONFIG_SCHED_DEBUG
REG("sched", S_IRUGO|S_IWUSR, proc_pid_sched_operations),
#endif
@@ -2836,7 +2908,9 @@ static const struct pid_entry tid_base_stuff[] = {
INF("auxv", S_IRUSR, proc_pid_auxv),
ONE("status", S_IRUGO, proc_pid_status),
ONE("personality", S_IRUSR, proc_pid_personality),
- INF("limits", S_IRUSR, proc_pid_limits),
+ NOD("limits", S_IFREG|S_IRUSR|S_IWUSR, NULL,
+ &proc_pid_limits_operations,
+ { .proc_read = proc_pid_limits }),
#ifdef CONFIG_SCHED_DEBUG
REG("sched", S_IRUGO|S_IWUSR, proc_pid_sched_operations),
#endif
--
1.6.3.3


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