Don't truncate /proc/PID/environ at 4096 characters

/proc/PID/environ currently truncates at 4096 characters, patch based on
the /proc/PID/mem code.

Signed-off-by: James Pearson <james-p@moving-picture.com>
Cc: Anton Arapov <aarapov@redhat.com>
Cc: Jan Engelhardt <jengelh@computergmbh.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 72 insertions, 23 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index ea115d4c9f59..4fe74d156416 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -199,27 +199,6 @@ static int proc_root_link(struct inode *inode, struct dentry **dentry, struct vf
          (task->state == TASK_STOPPED || task->state == TASK_TRACED) && \
          security_ptrace(current,task) == 0))
 
-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;
-
-                res = -ESRCH;
-                if (!ptrace_may_attach(task))
-                        goto out;
-
-                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);
-out:
-                mmput(mm);
-        }
-        return res;
-}
-
 static int proc_pid_cmdline(struct task_struct *task, char * buffer)
 {
         int res = 0;
@@ -658,6 +637,76 @@ static const 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_TEMPORARY);
+        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)
 {
@@ -2049,7 +2098,7 @@ static const struct pid_entry tgid_base_stuff[] = {
         DIR("task",       S_IRUGO|S_IXUGO, task),
         DIR("fd",         S_IRUSR|S_IXUSR, fd),
         DIR("fdinfo",     S_IRUSR|S_IXUSR, fdinfo),
-        INF("environ",    S_IRUSR, pid_environ),
+        REG("environ",    S_IRUSR, environ),
         INF("auxv",       S_IRUSR, pid_auxv),
         INF("status",     S_IRUGO, pid_status),
 #ifdef CONFIG_SCHED_DEBUG
@@ -2336,7 +2385,7 @@ out_no_task:
 static const struct pid_entry tid_base_stuff[] = {
         DIR("fd",        S_IRUSR|S_IXUSR, fd),
         DIR("fdinfo",    S_IRUSR|S_IXUSR, fdinfo),
-        INF("environ",   S_IRUSR, pid_environ),
+        REG("environ",   S_IRUSR, environ),
         INF("auxv",      S_IRUSR, pid_auxv),
         INF("status",    S_IRUGO, pid_status),
 #ifdef CONFIG_SCHED_DEBUG