Fix panic mounting unformatted zvol

On some older kernels, i.e. 2.6.18, zvol_ioctl_by_inode() may get passed a NULL
file pointer if the user tries to mount a zvol without a filesystem on it.
This change adds checks to prevent a null pointer dereference.

Closes #73.

Signed-off-by: Brian Behlendorf <[email protected]>

1 files changed, 4 insertions, 0 deletions

diff --git a/module/zfs/zvol.c b/module/zfs/zvol.c
index 6e9294292..b2a08fb43 100644
--- a/module/zfs/zvol.c
+++ b/module/zfs/zvol.c
@@ -1002,6 +1002,8 @@ static int
 zvol_ioctl_by_inode(struct inode *inode, struct file *file,
                     unsigned int cmd, unsigned long arg)
 {
+	if (file == NULL || inode == NULL)
+		return -EINVAL;
 	return zvol_ioctl(inode->i_bdev, file->f_mode, cmd, arg);
 }
 
@@ -1010,6 +1012,8 @@ static long
 zvol_compat_ioctl_by_inode(struct file *file,
                            unsigned int cmd, unsigned long arg)
 {
+	if (file == NULL)
+		return -EINVAL;
 	return zvol_compat_ioctl(file->f_dentry->d_inode->i_bdev,
 	                         file->f_mode, cmd, arg);
 }