mm: Create utility function for accessing a tasks commandline value

introduce get_cmdline() for retreiving the value of a processes proc/self/cmdline value. Acked-by: David Rientjes <rientjes@google.com> Acked-by: Stephen Smalley <sds@tycho.nsa.gov> Acked-by: Richard Guy Briggs <rgb@redhat.com> Signed-off-by: William Roberts <wroberts@tresys.com> Signed-off-by: Eric Paris <eparis@redhat.com>

mm: Create utility function for accessing a tasks commandline value
introduce get_cmdline() for retreiving the value of a processes proc/self/cmdline value. Acked-by: David Rientjes <rientjes@google.com> Acked-by: Stephen Smalley <sds@tycho.nsa.gov> Acked-by: Richard Guy Briggs <rgb@redhat.com> Signed-off-by: William Roberts <wroberts@tresys.com> Signed-off-by: Eric Paris <eparis@redhat.com>
William Roberts · Eric Paris
1 parent 147d2601d8
Showing 2 changed files with 49 additions and 0 deletions Side-by-side Diff
include/linux/mm.h
mm/util.c
@@ -1134,6 +1134,7 @@
 int set_page_dirty(struct page *page);
 int set_page_dirty_lock(struct page *page);
 int clear_page_dirty_for_io(struct page *page);
+int get_cmdline(struct task_struct *task, char *buffer, int buflen);
  
 /* Is the vma a continuation of the stack vma above it? */
 static inline int vma_growsdown(struct vm_area_struct *vma, unsigned long addr)
@@ -413,6 +413,54 @@
 		* sysctl_overcommit_ratio / 100) + total_swap_pages;
 }
  
+/**
+ * get_cmdline() - copy the cmdline value to a buffer.
+ * @task:     the task whose cmdline value to copy.
+ * @buffer:   the buffer to copy to.
+ * @buflen:   the length of the buffer. Larger cmdline values are truncated
+ *            to this length.
+ * Returns the size of the cmdline field copied. Note that the copy does
+ * not guarantee an ending NULL byte.
+ */
+int get_cmdline(struct task_struct *task, char *buffer, int buflen)
+{
+	int res = 0;
+	unsigned int len;
+	struct mm_struct *mm = get_task_mm(task);
+	if (!mm)
+		goto out;
+	if (!mm->arg_end)
+		goto out_mm;	/* Shh! No looking before we're done */
+
+	len = mm->arg_end - mm->arg_start;
+
+	if (len > buflen)
+		len = buflen;
+
+	res = access_process_vm(task, mm->arg_start, buffer, len, 0);
+
+	/*
+	 * If the nul at the end of args has been overwritten, then
+	 * assume application is using setproctitle(3).
+	 */
+	if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
+		len = strnlen(buffer, res);
+		if (len < res) {
+			res = len;
+		} else {
+			len = mm->env_end - mm->env_start;
+			if (len > buflen - res)
+				len = buflen - res;
+			res += access_process_vm(task, mm->env_start,
+						 buffer+res, len, 0);
+			res = strnlen(buffer, res);
+		}
+	}
+out_mm:
+	mmput(mm);
+out:
+	return res;
+}
  
 /* Tracepoints definitions. */
 EXPORT_TRACEPOINT_SYMBOL(kmalloc);
...	...	@@ -1134,6 +1134,7 @@
1134	1134	int set_page_dirty(struct page *page);
1135	1135	int set_page_dirty_lock(struct page *page);
1136	1136	int clear_page_dirty_for_io(struct page *page);
	1137	+int get_cmdline(struct task_struct task, char buffer, int buflen);
1137	1138
1138	1139	/* Is the vma a continuation of the stack vma above it? */
1139	1140	static inline int vma_growsdown(struct vm_area_struct *vma, unsigned long addr)
...	...	@@ -413,6 +413,54 @@
413	413	* sysctl_overcommit_ratio / 100) + total_swap_pages;
414	414	}
415	415
	416	+/**
	417	+ * get_cmdline() - copy the cmdline value to a buffer.
	418	+ * @task: the task whose cmdline value to copy.
	419	+ * @buffer: the buffer to copy to.
	420	+ * @buflen: the length of the buffer. Larger cmdline values are truncated
	421	+ * to this length.
	422	+ * Returns the size of the cmdline field copied. Note that the copy does
	423	+ * not guarantee an ending NULL byte.
	424	+ */
	425	+int get_cmdline(struct task_struct task, char buffer, int buflen)
	426	+{
	427	+ int res = 0;
	428	+ unsigned int len;
	429	+ struct mm_struct *mm = get_task_mm(task);
	430	+ if (!mm)
	431	+ goto out;
	432	+ if (!mm->arg_end)
	433	+ goto out_mm; /* Shh! No looking before we're done */
	434	+
	435	+ len = mm->arg_end - mm->arg_start;
	436	+
	437	+ if (len > buflen)
	438	+ len = buflen;
	439	+
	440	+ res = access_process_vm(task, mm->arg_start, buffer, len, 0);
	441	+
	442	+ /*
	443	+ * If the nul at the end of args has been overwritten, then
	444	+ * assume application is using setproctitle(3).
	445	+ */
	446	+ if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
	447	+ len = strnlen(buffer, res);
	448	+ if (len < res) {
	449	+ res = len;
	450	+ } else {
	451	+ len = mm->env_end - mm->env_start;
	452	+ if (len > buflen - res)
	453	+ len = buflen - res;
	454	+ res += access_process_vm(task, mm->env_start,
	455	+ buffer+res, len, 0);
	456	+ res = strnlen(buffer, res);
	457	+ }
	458	+ }
	459	+out_mm:
	460	+ mmput(mm);
	461	+out:
	462	+ return res;
	463	+}
416	464
417	465	/* Tracepoints definitions. */
418	466	EXPORT_TRACEPOINT_SYMBOL(kmalloc);