ext4: avoid declaring fs inconsistent due to invalid file handles

commit 8a363970d1dc38c4ec4ad575c862f776f468d057 upstream.

If we receive a file handle, either from NFS or open_by_handle_at(2),
and it points at an inode which has not been initialized, and the file
system has metadata checksums enabled, we shouldn't try to get the
inode, discover the checksum is invalid, and then declare the file
system as being inconsistent.

This can be reproduced by creating a test file system via "mke2fs -t
ext4 -O metadata_csum /tmp/foo.img 8M", mounting it, cd'ing into that
directory, and then running the following program.

#define _GNU_SOURCE
#include <fcntl.h>

struct handle {
	struct file_handle fh;
	unsigned char fid[MAX_HANDLE_SZ];
};

int main(int argc, char **argv)
{
	struct handle h = {{8, 1 }, { 12, }};

	open_by_handle_at(AT_FDCWD, &h.fh, O_RDONLY);
	return 0;
}

Google-Bug-Id: 120690101
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 13 insertions, 2 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 05eddfbd3404..032cf9b92665 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2459,8 +2459,19 @@ int do_journal_get_write_access(handle_t *handle,
 #define FALL_BACK_TO_NONDELALLOC 1
 #define CONVERT_INLINE_DATA	 2
 
-extern struct inode *ext4_iget(struct super_block *, unsigned long);
-extern struct inode *ext4_iget_normal(struct super_block *, unsigned long);
+typedef enum {
+	EXT4_IGET_NORMAL =	0,
+	EXT4_IGET_SPECIAL =	0x0001, /* OK to iget a system inode */
+	EXT4_IGET_HANDLE = 	0x0002	/* Inode # is from a handle */
+} ext4_iget_flags;
+
+extern struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
+				 ext4_iget_flags flags, const char *function,
+				 unsigned int line);
+
+#define ext4_iget(sb, ino, flags) \
+	__ext4_iget((sb), (ino), (flags), __func__, __LINE__)
+
 extern int  ext4_write_inode(struct inode *, struct writeback_control *);
 extern int  ext4_setattr(struct dentry *, struct iattr *);
 extern int  ext4_getattr(const struct path *, struct kstat *, u32, unsigned int);