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

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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.

Signed-off-by: Alessandro Schino <7991aleschino@gmail.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
This commit is contained in:
Alessandro Schino 2026-05-11 20:15:15 +02:00 committed by Konstantin Komarov
parent b7a9125cac
commit aa1bdbb39f
No known key found for this signature in database
GPG Key ID: A9B0331F832407B6
2 changed files with 7 additions and 1 deletions
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4
fs/ntfs3/dir.c
View File

@ -305,7 +305,9 @@ static inline bool ntfs_dir_emit(struct ntfs_sb_info *sbi,
if (sbi->options->nohidden && (fname->dup.fa & FILE_ATTRIBUTE_HIDDEN))
return true;
if (fname->name_len + sizeof(struct NTFS_DE) > le16_to_cpu(e->size))
if (sizeof(struct NTFS_DE) +
offsetof(struct ATTR_FILE_NAME, name) +
fname->name_len * sizeof(short) > le16_to_cpu(e->size))
return true;
name_len = ntfs_utf16_to_nls(sbi, fname->name, fname->name_len, name,

4
fs/ntfs3/index.c
View File

@ -789,6 +789,10 @@ static struct NTFS_DE *hdr_find_e(const struct ntfs_index *indx,
binary_search:
e_key_len = le16_to_cpu(e->key_size);
/* Validate key_size fits within the entry data area. */
if (e_key_len > le16_to_cpu(e->size) - sizeof(struct NTFS_DE))
return NULL;
diff2 = (*cmp)(key, key_len, e + 1, e_key_len, ctx);
if (diff2 > 0) {
if (found) {