From: Anton Arapov <aarapov@redhat.com>
Date: Thu, 27 Sep 2007 19:13:16 +0200
Subject: [misc] /proc/<pid>/environ stops at 4k bytes
Message-id: h8odfo3uc3.fsf@pepelac.englab.brq.redhat.com
O-Subject: [RHEL5.2 PATCH] BZ308391: /proc/<pid>/environ stops at 4k bytes
Bugzilla: 308391

BZ#308391:
  https://bugzilla.redhat.com/show_bug.cgi?id=308391

Description:
  On the current kernels, when a process has more than 4k of data in
its environment, /proc/<pid>/environ shows only the first 4k.

Upstream status:
  Patch has been added to the -mm tree.
  http://marc.info/?l=linux-mm-commits&m=119084591013320&w=2

Test status:
  Patch has been tested for compilation and boot. Issue has been
reproduced. Patch fixes it.

Notice:
  BZ#254037 - RHEL4 clone of this bug.

==

Acked-by: Larry Woodman <lwoodman@redhat.com>
Acked-by: Prarit Bhargava <prarit@redhat.com>

Acked-by: Jon Masters <jcm@redhat.com>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index e05b338..f051e75 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -466,22 +466,6 @@ out:
 	return NULL;
 }
 
-static int proc_pid_environ(struct task_struct *task, char * buffer)
-{
-	int res = 0;
-	struct mm_struct *mm = get_task_mm(task);
-	if (mm) {
-		unsigned int len = mm->env_end - mm->env_start;
-		if (len > PAGE_SIZE)
-			len = PAGE_SIZE;
-		res = access_process_vm(task, mm->env_start, buffer, len, 0);
-		if (!ptrace_may_attach(task))
-			res = -ESRCH;
-		mmput(mm);
-	}
-	return res;
-}
-
 static int proc_pid_cmdline(struct task_struct *task, char * buffer)
 {
 	int res = 0;
@@ -922,6 +906,75 @@ static struct file_operations proc_mem_operations = {
 	.open		= mem_open,
 };
 
+static ssize_t environ_read(struct file *file, char __user *buf, 
+			    size_t count, loff_t *ppos)
+{
+	struct task_struct *task = get_proc_task(file->f_dentry->d_inode);
+	char *page;
+	unsigned long src = *ppos;
+	int ret = -ESRCH;
+	struct mm_struct *mm;
+
+	if (!task)
+		goto out_no_task;
+
+	if (!ptrace_may_attach(task))
+		goto out;
+
+	ret = -ENOMEM;
+	page = (char *)__get_free_page(GFP_USER);
+	if (!page)
+		goto out;
+
+	ret = 0;
+
+	mm = get_task_mm(task);
+	if (!mm)
+		goto out_free;
+
+	while (count > 0) {
+		int this_len, retval, max_len;
+
+		this_len = mm->env_end - (mm->env_start + src);
+
+		if (this_len <= 0)
+			break;
+
+		max_len = (count > PAGE_SIZE) ? PAGE_SIZE : count;
+		this_len = (this_len > max_len) ? max_len : this_len;
+
+		retval = access_process_vm(task, (mm->env_start + src),
+					    page, this_len, 0);
+
+		if (retval <= 0) {
+			ret = retval;
+			break;
+		}
+
+		if (copy_to_user(buf, page, retval)) {
+			ret = -EFAULT;
+			break;
+		}
+
+		ret += retval;
+		src += retval;
+		buf += retval;
+		count -= retval;
+	}
+	*ppos = src;
+	mmput(mm);
+out_free:
+	free_page((unsigned long) page);
+out:
+	put_task_struct(task);
+out_no_task:
+	return ret;
+}
+
+static const struct file_operations proc_environ_operations = {
+	.read           = environ_read,
+};
+
 static ssize_t oom_adjust_read(struct file *file, char __user *buf,
 				size_t count, loff_t *ppos)
 {
@@ -1765,8 +1818,7 @@ static struct dentry *proc_pident_lookup(struct inode *dir,
 			break;
 		case PROC_TID_ENVIRON:
 		case PROC_TGID_ENVIRON:
-			inode->i_fop = &proc_info_file_operations;
-			ei->op.proc_read = proc_pid_environ;
+			inode->i_fop = &proc_environ_operations;
 			break;
 		case PROC_TID_AUXV:
 		case PROC_TGID_AUXV: