From: Alexandro Calo Date: Thu, 16 Jul 2026 11:30:04 +0200 Subject: [PATCH] fs/ntfs: Fix index_root heap OOB write in ntfs_ir_to_ib() ntfs_ir_to_ib copies all entries from index_root into a freshly allocated index_block_size-byte buffer without verifying that the entries fit in the available space. The entries in index_root may be larger than the usable entry space in the index block. This can cause OOB writes past the end of the allocation. The validator ntfs_index_root_inconsistent() checks that entries are self-consistent within the IR value, but never cross-checks them against index_block_size. There is no bounds check in ntfs_ir_to_ib() before the memcpy. Fixing this at the sink in ntfs_ir_to_ib() since ntfs_index_root_inconsistent() validates the logical consistency of index_root as a structure and a root with large entries is a structurally valid root. The bug is a size conflict of ntfs_ir_to_ib(). Also, the validator is called once per inode load in ntfs_read_locked_inode() while ntfs_ir_to_ib() is only called during a reparent, a check there adds no overhead to the common path. Moreover, even a future call path that bypasses the validator would still be protected. This heap out-of-bounds write is triggered by a crafted filesystem image, which is not in the kernel threat model, anyway, fixing memory errors would be nice to keep things secure. Signed-off-by: Alexandro Calo --- fs/ntfs/index.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/fs/ntfs/index.c b/fs/ntfs/index.c index faa7ee920a3a..529697b5891e 100644 --- a/fs/ntfs/index.c +++ b/fs/ntfs/index.c @@ -1112,6 +1112,7 @@ static struct index_block *ntfs_ir_to_ib(struct index_root *ir, s64 ib_vcn) struct index_entry *ie_last; char *ies_start, *ies_end; int i; + u32 ib_cap; ntfs_debug("Entering\n"); @@ -1127,6 +1128,15 @@ static struct index_block *ntfs_ir_to_ib(struct index_root *ir, s64 ib_vcn) * as well, which can never have any data. */ i = (char *)ie_last - ies_start + le16_to_cpu(ie_last->length); + + /* Entries must fit in the allocated index block */ + ib_cap = le32_to_cpu(ib->index.allocated_size) + - le32_to_cpu(ib->index.entries_offset); + if ((u32)i > ib_cap) { + kvfree(ib); + return NULL; + } + memcpy(ntfs_ie_get_first(&ib->index), ies_start, i); ib->index.flags = ir->index.flags; base-commit: 37e2f878a7a660a216cc7a60459995fefd150f25 -- 2.47.3