CVE-2024-56624

In the Linux kernel, the following vulnerability has been resolved:

iommufd: Fix out_fput in iommufd_fault_alloc()

As fput() calls the file->f_op->release op, where fault obj and ictx are getting released, there is no need to release these two after fput() one more time, which would result in imbalanced refcounts: refcount_t: decrement hit 0; leaking memory. WARNING: CPU: 48 PID: 2369 at lib/refcount.c:31 refcount_warn_saturate+0x60/0x230 Call trace: refcount_warn_saturate+0x60/0x230 (P) refcount_warn_saturate+0x60/0x230 (L) iommufd_fault_fops_release+0x9c/0xe0 [iommufd] ... VFS: Close: file count is 0 (f_op=iommufd_fops [iommufd]) WARNING: CPU: 48 PID: 2369 at fs/open.c:1507 filp_flush+0x3c/0xf0 Call trace: filp_flush+0x3c/0xf0 (P) filp_flush+0x3c/0xf0 (L) __arm64_sys_close+0x34/0x98 ... imbalanced put on file reference count WARNING: CPU: 48 PID: 2369 at fs/file.c:74 __file_ref_put+0x100/0x138 Call trace: __file_ref_put+0x100/0x138 (P) __file_ref_put+0x100/0x138 (L) __fput_sync+0x4c/0xd0

Drop those two lines to fix the warnings above.

A low severity flaw was found in the Linux kernel's iommufd subsystem. In the error path of iommufd_fault_alloc(), the iommufd fault object and ictx are released after fput() has already released them through the file's f_op->release operation, resulting in imbalanced reference counts: the reference count can be decremented to zero prematurely, leaking memory and triggering refcount saturation and file count warnings. A local user able to trigger this fault-allocation failure path through the iommufd interface could use this flaw to leak kernel memory and cause kernel warnings, impacting system availability; no confidentiality or integrity impact is expected. For this reason Red Hat rates this flaw Low severity, and the Red Hat CVSS 3.1 score of 5.5 (AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H) reflects availability-only impact. This differs from the CVE.org score of 7.8, which assigns high confidentiality and integrity impacts that the available technical evidence does not support. Red Hat Enterprise Linux 9 kernel and kernel-rt are affected; because of the low severity and the limited, local availability-only impact of this error-path flaw, the fix is deferred to a future Red Hat Enterprise Linux 9 update, leaving a residual risk of kernel warnings and memory leaks when the error path is triggered. Red Hat Enterprise Linux 6, 7, and 8 and the Hosted OpenShift (ARO/OSD) streams are not affected by this flaw.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.