Re: [PATCH v2] ima: initialize the real inode attributes of the iint cache

[sashiko-bot@kernel.org]

> ima_iint_cache objects are allocated with kmem_cache_alloc() from a
> dedicated slab whose constructor only runs once, when the slab is first
> created; the constructor does not run again when a freed object is
> reallocated.  ima_iint_init_always() resets all iint fields except
> real_inode.ino and real_inode.dev, which therefore keep the values of
> the previously freed iint.
> 
> integrity_inode_attrs_changed() reads those fields in
> process_measurement() to detect changes to the backing file on stacked
> filesystems.  The fields are normally written by
> integrity_inode_attrs_store() from ima_collect_measurement(), but the
> IMA_HASH path sets IMA_HASHED without calling it, so on the next file
> open the stale, uninitialized ino and dev are read.  Depending on the
> residual values, IMA may skip re-evaluating a file whose backing data
> or metadata changed, or needlessly re-evaluate it.
> 
> At allocation time there are no valid real-inode attributes yet, so
> clear the entire real_inode structure.  On stacked filesystems the
> first comparison against the underlying real inode will then fail until
> ima_collect_measurement() stores the real inode's attributes, which is
> the safe, conservative direction.
> 
> Fixes: b836c4d29f27 ("ima: detect changes to the backing overlay file")
> Signed-off-by: Cai Xinchen <caixinchen1@huawei.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261103034320.1756673-1-caixinchen1@huawei.com?part=1