Fix zil_commit() NULL dereference

Update the current code to ensure inodes are never dirtied if they are
part of a read-only file system or snapshot.  If they do somehow get
dirtied an attempt will make made to write them to disk.  In the case
of snapshots, which don't have a ZIL, this will result in a NULL
dereference in zil_commit().

Signed-off-by: Richard Yao <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #2405

5 files changed, 24 insertions, 6 deletions

diff --git a/include/sys/zfs_znode.h b/include/sys/zfs_znode.h
index a0200684e..4bb8a7761 100644
--- a/include/sys/zfs_znode.h
+++ b/include/sys/zfs_znode.h
@@ -337,6 +337,7 @@ extern void	zfs_znode_dmu_fini(znode_t *);
 extern int	zfs_inode_alloc(struct super_block *, struct inode **ip);
 extern void	zfs_inode_destroy(struct inode *);
 extern void	zfs_inode_update(znode_t *);
+extern void	zfs_mark_inode_dirty(struct inode *);
 
 extern void zfs_log_create(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
     znode_t *dzp, znode_t *zp, char *name, vsecattr_t *, zfs_fuid_info_t *,
diff --git a/module/zfs/zfs_vnops.c b/module/zfs/zfs_vnops.c
index 91f743aaa..4f531733e 100644
--- a/module/zfs/zfs_vnops.c
+++ b/module/zfs/zfs_vnops.c
@@ -3965,7 +3965,8 @@ zfs_putpage(struct inode *ip, struct page *pp, struct writeback_control *wbc)
 		 * writepages() normally handles the entire commit for
 		 * performance reasons.
 		 */
-		zil_commit(zsb->z_log, zp->z_id);
+		if (zsb->z_log != NULL)
+			zil_commit(zsb->z_log, zp->z_id);
 	}
 
 	ZFS_EXIT(zsb);
diff --git a/module/zfs/zfs_znode.c b/module/zfs/zfs_znode.c
index 8cd0d8379..23e090712 100644
--- a/module/zfs/zfs_znode.c
+++ b/module/zfs/zfs_znode.c
@@ -511,6 +511,21 @@ zfs_inode_update(znode_t *zp)
 	spin_unlock(&ip->i_lock);
 }
 
+/*
+ * Safely mark an inode dirty.  Inodes which are part of a read-only
+ * file system or snapshot may not be dirtied.
+ */
+void
+zfs_mark_inode_dirty(struct inode *ip)
+{
+	zfs_sb_t *zsb = ITOZSB(ip);
+
+	if (zfs_is_readonly(zsb) || dmu_objset_is_snapshot(zsb->z_os))
+		return;
+
+	mark_inode_dirty(ip);
+}
+
 static uint64_t empty_xattr;
 static uint64_t pad[4];
 static zfs_acl_phys_t acl_phys;
diff --git a/module/zfs/zpl_file.c b/module/zfs/zpl_file.c
index 2a7bcb9b0..d37cf07f9 100644
--- a/module/zfs/zpl_file.c
+++ b/module/zfs/zpl_file.c
@@ -55,7 +55,7 @@ zpl_release(struct inode *ip, struct file *filp)
 	int error;
 
 	if (ITOZ(ip)->z_atime_dirty)
-		mark_inode_dirty(ip);
+		zfs_mark_inode_dirty(ip);
 
 	crhold(cr);
 	error = -zfs_close(ip, filp->f_flags, cr);
@@ -445,7 +445,8 @@ zpl_writepages(struct address_space *mapping, struct writeback_control *wbc)
 	if (sync_mode != wbc->sync_mode) {
 		ZFS_ENTER(zsb);
 		ZFS_VERIFY_ZP(zp);
-		zil_commit(zsb->z_log, zp->z_id);
+		if (zsb->z_log != NULL)
+			zil_commit(zsb->z_log, zp->z_id);
 		ZFS_EXIT(zsb);
 
 		/*
diff --git a/module/zfs/zpl_xattr.c b/module/zfs/zpl_xattr.c
index c5c15a2dd..107b80300 100644
--- a/module/zfs/zpl_xattr.c
+++ b/module/zfs/zpl_xattr.c
@@ -751,7 +751,7 @@ zpl_set_acl(struct inode *ip, int type, struct posix_acl *acl)
 				if (ip->i_mode != mode) {
 					ip->i_mode = mode;
 					ip->i_ctime = current_fs_time(sb);
-					mark_inode_dirty(ip);
+					zfs_mark_inode_dirty(ip);
 				}
 
 				if (error == 0)
@@ -909,7 +909,7 @@ zpl_init_acl(struct inode *ip, struct inode *dir)
 		if (!acl) {
 			ip->i_mode &= ~current_umask();
 			ip->i_ctime = current_fs_time(ITOZSB(ip)->z_sb);
-			mark_inode_dirty(ip);
+			zfs_mark_inode_dirty(ip);
 			return (0);
 		}
 	}
@@ -927,7 +927,7 @@ zpl_init_acl(struct inode *ip, struct inode *dir)
 		error = __posix_acl_create(&acl, GFP_KERNEL, &mode);
 		if (error >= 0) {
 			ip->i_mode = mode;
-			mark_inode_dirty(ip);
+			zfs_mark_inode_dirty(ip);
 			if (error > 0)
 				error = zpl_set_acl(ip, ACL_TYPE_ACCESS, acl);
 		}