CVE-2022-49899

What it is

In the Linux kernel, the following vulnerability has been resolved: fscrypt: stop using keyrings subsystem for fscrypt_master_key The approach of fs/crypto/ internally managing the fscrypt_master_key structs as the payloads of "struct key" objects contained in a "struct key" keyring has outlived its usefulness. The original idea was to simplify the code by reusing code from the keyrings subsystem. However, several issues have arisen that can't easily be resolved: - When a master key struct is destroyed, blk_crypto_evict_key() must be called on any per-mode keys embedded in it. (This started being the case when inline encryption support was added.) Yet, the keyrings subsystem can arbitrarily delay the destruction of keys, even past the time the filesystem was unmounted. Therefore, currently there is no easy way to call blk_crypto_evict_key() when a master key is destroyed. Currently, this is worked around by holding an extra reference to the filesystem's request_queue(s). But it was overlooked that the request_queue reference is *not* guaranteed to pin the corresponding blk_crypto_profile too; for device-mapper devices that support inline crypto, it doesn't. This can cause a use-after-free. - When the last inode that was using an incompletely-removed master key is evicted, the master key removal is completed by removing the key struct from the keyring. Currently this is done via key_invalidate(). Yet, key_invalidate() takes the key semaphore. This can deadlock when called from the shrinker, since in fscrypt_ioctl_add_key(), memory is allocated with GFP_KERNEL under the same semaphore. - More generally, the fact that the keyrings subsystem can arbitrarily delay the destruction of keys (via garbage collection delay, or via random processes getting temporary key references) is undesirable, as it means we can't strictly guarantee that all secrets are ever wiped. - Doing the master key lookups via the keyrings subsystem results in the key_permission LSM hook being called. fscrypt doesn't want this, as all access control for encrypted files is designed to happen via the files themselves, like any other files. The workaround which SELinux users are using is to change their SELinux policy to grant key search access to all domains. This works, but it is an odd extra step that shouldn't really have to be done. The fix for all these issues is to change the implementation to what I should have done originally: don't use the keyrings subsystem to keep track of the filesystem's fscrypt_master_key structs. Instead, just store them in a regular kernel data structure, and rework the reference counting, locking, and lifetime accordingly. Retain support for RCU-mode key lookups by using a hash table. Replace fscrypt_sb_free() with fscrypt_sb_delete(), which releases the keys synchronously and runs a bit earlier during unmount, so that block devices are still available. A side effect of this patch is that neither the master keys themselves nor the filesystem keyrings will be listed in /proc/keys anymore. ("Master key users" and the master key users keyrings will still be listed.) However, this was mostly an implementation detail, and it was intended just for debugging purposes. I don't know of anyone using it. This patch does *not* change how "master key users" (->mk_users) works; that still uses the keyrings subsystem. That is still needed for key quotas, and changing that isn't necessary to solve the issues listed above. If we decide to change that too, it would be a separate patch. I've marked this as fixing the original commit that added the fscrypt keyring, but as noted above the most important issue that this patch fixes wasn't introduced until the addition of inline encryption support.

At a glance

Exploitability

Can be exploited locally on the machine with a low-privilege account. High risk of data exposure, data tampering, service disruption.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2025-05-01 15:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-08-04 10:17 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.2% in the next 30 days (EPSS).
• Severity: 7.8 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2025-05-01 15:16 UTC

Last modified

2026-08-04 10:17 UTC

Exploit probability

0.2% · EPSS, next 30 days

Record status

Modified

Affected

• Linux Kernel < 5.10.154
• Linux Kernel < 5.15.78
• Linux Kernel < 6.0.8

Attack profile CVSS 3.1 · 7.8

Attack vector

Local

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2022-49899.md and follow it. Check whether this project is affected by CVE-2022-49899. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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