fs/proc/base.c: fix proc_fault_inject_write() input sanity check

Remove obfuscated zero-length input check and return -EINVAL instead of
-EIO error to make the error message clear to user.  Add whitespace
stripping.  No functionality changes.

The old code:

echo  1  > /proc/pid/make-it-fail (ok)
echo 1foo > /proc/pid/make-it-fail (-bash: echo: write error: Input/output error)

The new code:

echo  1  > /proc/pid/make-it-fail (ok)
echo 1foo > /proc/pid/make-it-fail (-bash: echo: write error: Invalid argument)

This patch is conservative in changes to not breaking existing
scripts/applications.

Signed-off-by: Vincent Li <macli@brc.ubc.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 6 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 5bc587049b37..837469a96598 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1187,17 +1187,16 @@ static ssize_t proc_fault_inject_write(struct file * file,
                 count = sizeof(buffer) - 1;
         if (copy_from_user(buffer, buf, count))
                 return -EFAULT;
-        make_it_fail = simple_strtol(buffer, &end, 0);
-        if (*end == '\n')
-                end++;
+        make_it_fail = simple_strtol(strstrip(buffer), &end, 0);
+        if (*end)
+                return -EINVAL;
         task = get_proc_task(file->f_dentry->d_inode);
         if (!task)
                 return -ESRCH;
         task->make_it_fail = make_it_fail;
         put_task_struct(task);
-        if (end - buffer == 0)
-                return -EIO;
-        return end - buffer;
+
+        return count;
 }
 
 static const struct file_operations proc_fault_inject_operations = {