CVE-2024-26689: ceph: prevent use-after-free in encode_cap_msg()

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-04-03 · updated 2026-08-04
Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: ceph: prevent use-after-free in encode_cap_msg() In fs/ceph/caps.c, in encode_cap_msg(), "use after free" error was caught by KASAN at this line - 'ceph_buffer_get(arg->xattr_buf);'. This implies before the refcount could be increment here, it was freed. In same file, in "handle_cap_grant()" refcount is decremented by this line - 'ceph_buffer_put(ci->i_xattrs.blob);'. It appears that a race occurred and resource was freed by the latter line before the former line could increment it. encode_cap_msg() is called by __send_cap() and __send_cap() is called by ceph_check_caps() after calling __prep_cap(). __prep_cap() is where arg->xattr_buf is assigned to ci->i_xattrs.blob. This is the spot where the refcount must be increased to prevent "use after free" error.

Affected products

Debian Linux: 10.0
Linux kernel: before 5.10.210; from 5.11 before 5.15.149; from 5.16 before 6.1.79; from 6.2 before 6.6.18; from 6.7 before 6.7.6; 6.8-rc1, 6.8-rc2, 6.8-rc3 — fixed in 5.10.210, 5.15.149, 6.1.79, 6.6.18, 6.7.6

How to fix

Upgrade to a fixed version: Linux kernel 5.10.210, 5.15.149, 6.1.79, 6.6.18. Check the vendor advisory for mitigations.

References

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