From: Bryam Vargas Date: Sun, 7 Jun 2026 20:30:00 +0000 (+0000) Subject: ntfs: bound the look-ahead attribute-list entry in ntfs_external_attr_find() X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=344b18f389f9934d59c7b0cf3d20541ea2e0da58;p=thirdparty%2Fkernel%2Flinux.git ntfs: bound the look-ahead attribute-list entry in ntfs_external_attr_find() When resolving an attribute lookup with a non-zero @lowest_vcn, ntfs_external_attr_find() peeks at the next $ATTRIBUTE_LIST entry to decide whether to keep searching, but bounds that not-yet-validated entry only with "(u8 *)next_al_entry + 6 < al_end" (which proves just bytes 0..6 are in range) and "(u8 *)next_al_entry + length <= al_end" with an attacker-controlled, non-8-aligned length. It then reads next_al_entry->lowest_vcn (an __le64 at offset 8) and the name at next_al_entry->name_offset, both of which can lie past al_end -- the exact end of the kvmalloc'd attribute-list buffer (allocated at the on-disk attr_list_size, no rounding). A crafted on-disk $ATTRIBUTE_LIST whose last entry sits a few bytes before al_end therefore yields a slab out-of-bounds read when the inode is read. Validate the look-ahead entry with ntfs_attr_list_entry_is_valid() (added in patch 1/3) before dereferencing lowest_vcn and the name, so the same fixed-header, length and name bounds the main attribute-list walk uses now guard this read too. Fixes: 1e9ea7e04472 ("Revert "fs: Remove NTFS classic"") Signed-off-by: Bryam Vargas Reviewed-by: Hyunchul Lee Signed-off-by: Namjae Jeon --- diff --git a/fs/ntfs/attrib.c b/fs/ntfs/attrib.c index 2d675bf99ca7..1e0076ef81ef 100644 --- a/fs/ntfs/attrib.c +++ b/fs/ntfs/attrib.c @@ -1263,9 +1263,8 @@ find_attr_list_attr: * we have reached the right one or the search has failed. */ if (lowest_vcn && (u8 *)next_al_entry >= al_start && - (u8 *)next_al_entry + 6 < al_end && - (u8 *)next_al_entry + le16_to_cpu( - next_al_entry->length) <= al_end && + ntfs_attr_list_entry_is_valid(next_al_entry, + al_end) && le64_to_cpu(next_al_entry->lowest_vcn) <= lowest_vcn && next_al_entry->type == al_entry->type &&