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ext4: verify fast symlink length

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Verify fast symlink length stored in inode->i_size matches the string
stored in the inode to avoid surprises from corrupted filesystems.

Reported-by: syzbot+48a99e426f29859818c0@syzkaller.appspotmail.com
Tested-by: syzbot+48a99e426f29859818c0@syzkaller.appspotmail.com
Fixes: bae80473f7b0 ("ext4: use inode_set_cached_link()")
Suggested-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://patch.msgid.link/20250206094454.20522-2-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Jan Kara 2025-02-06 10:44:55 +01:00 committed by Theodore Ts'o
parent c8e008b604
commit 5f920d5d60
1 changed files with 10 additions and 2 deletions

12
fs/ext4/inode.c

@ -5029,8 +5029,16 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
inode->i_op = &ext4_encrypted_symlink_inode_operations;
} else if (ext4_inode_is_fast_symlink(inode)) {
inode->i_op = &ext4_fast_symlink_inode_operations;
nd_terminate_link(ei->i_data, inode->i_size,
sizeof(ei->i_data) - 1);
if (inode->i_size == 0 ||
inode->i_size >= sizeof(ei->i_data) ||
strnlen((char *)ei->i_data, inode->i_size + 1) !=
inode->i_size) {
ext4_error_inode(inode, function, line, 0,
"invalid fast symlink length %llu",
(unsigned long long)inode->i_size);
ret = -EFSCORRUPTED;
goto bad_inode;
}
inode_set_cached_link(inode, (char *)ei->i_data,
inode->i_size);
} else {