ntfs3: fix out-of-bounds read in ntfs_dir_emit() and hdr_find_e()

Summary

In the Linux kernel, the following vulnerability has been resolved: ntfs3: fix out-of-bounds read in ntfs_dir_emit() and hdr_find_e() The bounds check in ntfs_dir_emit() compares fname->name_len (a character count) against e->size (a byte count) without accounting for the 2-byte-per-character UTF-16LE encoding or the ATTR_FILE_NAME header size: if (fname->name_len + sizeof(struct NTFS_DE) > le16_to_cpu(e->size)) This computes: name_len + 16 > e_size The correct check must account for the ATTR_FILE_NAME header (66 bytes before the name) and the UTF-16LE character size (2 bytes each): sizeof(NTFS_DE) + offsetof(ATTR_FILE_NAME, name) + name_len * sizeof(short) > e_size Which computes: 16 + 66 + name_len * 2 > e_size The correct calculation already exists as fname_full_size() in ntfs.h and is used in cmp_fnames(), namei.c, and fslog.c, but was not used in the readdir path. A crafted NTFS image with an index entry containing a small e->size but large fname->name_len bypasses the current check, causing ntfs_utf16_to_nls() to read past the entry boundary. Additionally, add a key_size validation in hdr_find_e() to ensure the declared key_size does not exceed the available entry data, preventing comparison functions from reading past entry boundaries on the lookup path.