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ntfs: update index root allocated size before shrink

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ntfs_ir_truncate() currently shrinks the resident $INDEX_ROOT value first
and only updates index.allocated_size after re-looking up the attribute.
During that relookup, the resident value_length can already be smaller
while index.allocated_size still contains the old larger size.

That leaves a transiently inconsistent $INDEX_ROOT layout and prevents
lookup-time $INDEX_ROOT validation from being enabled: validation can
correctly reject allocated_size extending past the newly shrunk resident
value.

When shrinking, lower index.allocated_size before shrinking value_length.
If the truncate fails, restore the old allocated_size. Keep the existing
grow ordering because the old allocated_size remains within the enlarged
resident value until it is updated after the relookup. The shrink path is
safe because the new value_length still covers struct index_root, so the
index.allocated_size field remains present while it is updated first.

Cc: stable@vger.kernel.org # v7.1
Signed-off-by: DaeMyung Kang <charsyam@gmail.com>
Reviewed-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
This commit is contained in:
DaeMyung Kang 2026-06-09 00:49:16 +09:00 committed by Namjae Jeon
parent 0bb508fb3b
commit e782ca90ce
1 changed files with 15 additions and 3 deletions
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18
fs/ntfs/index.c
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@ -1365,9 +1365,16 @@ static int ntfs_ir_reparent(struct ntfs_index_context *icx)
static int ntfs_ir_truncate(struct ntfs_index_context *icx, int data_size)
{
int ret;
u32 old_allocated_size;
bool shrink;
ntfs_debug("Entering\n");
old_allocated_size = le32_to_cpu(icx->ir->index.allocated_size);
shrink = data_size < old_allocated_size;
if (shrink)
icx->ir->index.allocated_size = cpu_to_le32(data_size);
/*
* INDEX_ROOT must be resident and its entries can be moved to
* struct index_block, so ENOSPC isn't a real error.
@ -1379,9 +1386,14 @@ static int ntfs_ir_truncate(struct ntfs_index_context *icx, int data_size)
if (!icx->ir)
return -ENOENT;
icx->ir->index.allocated_size = cpu_to_le32(data_size);
} else if (ret != -ENOSPC)
ntfs_error(icx->idx_ni->vol->sb, "Failed to truncate INDEX_ROOT");
if (!shrink)
icx->ir->index.allocated_size = cpu_to_le32(data_size);
} else {
if (shrink)
icx->ir->index.allocated_size = cpu_to_le32(old_allocated_size);
if (ret != -ENOSPC)
ntfs_error(icx->idx_ni->vol->sb, "Failed to truncate INDEX_ROOT");
}
return ret;
}