ext4: avoid declaring fs inconsistent due to invalid file handles

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

1 files changed, 37 insertions, 17 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 22a9d8159720..664b434ba836 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4817,7 +4817,9 @@ static inline u64 ext4_inode_peek_iversion(const struct inode *inode)
 		return inode_peek_iversion(inode);
 }
 
-struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
+struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
+			  ext4_iget_flags flags, const char *function,
+			  unsigned int line)
 {
 	struct ext4_iloc iloc;
 	struct ext4_inode *raw_inode;
@@ -4831,6 +4833,18 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
 	gid_t i_gid;
 	projid_t i_projid;
 
+	if (((flags & EXT4_IGET_NORMAL) &&
+	     (ino < EXT4_FIRST_INO(sb) && ino != EXT4_ROOT_INO)) ||
+	    (ino < EXT4_ROOT_INO) ||
+	    (ino > le32_to_cpu(EXT4_SB(sb)->s_es->s_inodes_count))) {
+		if (flags & EXT4_IGET_HANDLE)
+			return ERR_PTR(-ESTALE);
+		__ext4_error(sb, function, line,
+			     "inode #%lu: comm %s: iget: illegal inode #",
+			     ino, current->comm);
+		return ERR_PTR(-EFSCORRUPTED);
+	}
+
 	inode = iget_locked(sb, ino);
 	if (!inode)
 		return ERR_PTR(-ENOMEM);
@@ -4846,18 +4860,26 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
 	raw_inode = ext4_raw_inode(&iloc);
 
 	if ((ino == EXT4_ROOT_INO) && (raw_inode->i_links_count == 0)) {
-		EXT4_ERROR_INODE(inode, "root inode unallocated");
+		ext4_error_inode(inode, function, line, 0,
+				 "iget: root inode unallocated");
 		ret = -EFSCORRUPTED;
 		goto bad_inode;
 	}
 
+	if ((flags & EXT4_IGET_HANDLE) &&
+	    (raw_inode->i_links_count == 0) && (raw_inode->i_mode == 0)) {
+		ret = -ESTALE;
+		goto bad_inode;
+	}
+
 	if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) {
 		ei->i_extra_isize = le16_to_cpu(raw_inode->i_extra_isize);
 		if (EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize >
 			EXT4_INODE_SIZE(inode->i_sb) ||
 		    (ei->i_extra_isize & 3)) {
-			EXT4_ERROR_INODE(inode,
-					 "bad extra_isize %u (inode size %u)",
+			ext4_error_inode(inode, function, line, 0,
+					 "iget: bad extra_isize %u "
+					 "(inode size %u)",
 					 ei->i_extra_isize,
 					 EXT4_INODE_SIZE(inode->i_sb));
 			ret = -EFSCORRUPTED;
@@ -4879,7 +4901,8 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
 	}
 
 	if (!ext4_inode_csum_verify(inode, raw_inode, ei)) {
-		EXT4_ERROR_INODE(inode, "checksum invalid");
+		ext4_error_inode(inode, function, line, 0,
+				 "iget: checksum invalid");
 		ret = -EFSBADCRC;
 		goto bad_inode;
 	}
@@ -4936,7 +4959,8 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
 			((__u64)le16_to_cpu(raw_inode->i_file_acl_high)) << 32;
 	inode->i_size = ext4_isize(sb, raw_inode);
 	if ((size = i_size_read(inode)) < 0) {
-		EXT4_ERROR_INODE(inode, "bad i_size value: %lld", size);
+		ext4_error_inode(inode, function, line, 0,
+				 "iget: bad i_size value: %lld", size);
 		ret = -EFSCORRUPTED;
 		goto bad_inode;
 	}
@@ -5012,7 +5036,8 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
 	ret = 0;
 	if (ei->i_file_acl &&
 	    !ext4_data_block_valid(EXT4_SB(sb), ei->i_file_acl, 1)) {
-		EXT4_ERROR_INODE(inode, "bad extended attribute block %llu",
+		ext4_error_inode(inode, function, line, 0,
+				 "iget: bad extended attribute block %llu",
 				 ei->i_file_acl);
 		ret = -EFSCORRUPTED;
 		goto bad_inode;
@@ -5040,8 +5065,9 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
 	} else if (S_ISLNK(inode->i_mode)) {
 		/* VFS does not allow setting these so must be corruption */
 		if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) {
-			EXT4_ERROR_INODE(inode,
-			  "immutable or append flags not allowed on symlinks");
+			ext4_error_inode(inode, function, line, 0,
+					 "iget: immutable or append flags "
+					 "not allowed on symlinks");
 			ret = -EFSCORRUPTED;
 			goto bad_inode;
 		}
@@ -5071,7 +5097,8 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
 		make_bad_inode(inode);
 	} else {
 		ret = -EFSCORRUPTED;
-		EXT4_ERROR_INODE(inode, "bogus i_mode (%o)", inode->i_mode);
+		ext4_error_inode(inode, function, line, 0,
+				 "iget: bogus i_mode (%o)", inode->i_mode);
 		goto bad_inode;
 	}
 	brelse(iloc.bh);
@@ -5085,13 +5112,6 @@ bad_inode:
 	return ERR_PTR(ret);
 }
 
-struct inode *ext4_iget_normal(struct super_block *sb, unsigned long ino)
-{
-	if (ino < EXT4_FIRST_INO(sb) && ino != EXT4_ROOT_INO)
-		return ERR_PTR(-EFSCORRUPTED);
-	return ext4_iget(sb, ino);
-}
-
 static int ext4_inode_blocks_set(handle_t *handle,
 				struct ext4_inode *raw_inode,
 				struct ext4_inode_info *ei)