From dc09bf79b76f9a7157e225f449655f3f62f96c9c Mon Sep 17 00:00:00 2001 From: Alexandro Calo Date: Fri, 17 Jul 2026 12:14:51 +0200 Subject: [PATCH] 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. With NULL as first parameter of ntfs_error(), the volume error flag is never set by this call, so the device name will be absent from the error message. In any case, that the caller, ntfs_ir_reparent(), prints an error message that includes the device name on NULL returns. I think this is the best solution available without adding 'struct super_block *sb' as a parameter to ntfs_ir_to_ib(). 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. Fixes: 0a8ac0c1fa0b ("ntfs: update directory operations") Signed-off-by: Alexandro Calo Reviewed-by: Hyunchul Lee Signed-off-by: Namjae Jeon --- fs/ntfs/index.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/fs/ntfs/index.c b/fs/ntfs/index.c index faa7ee920a3a..409759eab55d 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 +1128,16 @@ 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) { + ntfs_error(NULL, "Entries (%d B) exceed IB capacity", i); + kvfree(ib); + return NULL; + } + memcpy(ntfs_ie_get_first(&ib->index), ies_start, i); ib->index.flags = ir->index.flags;