Use After Free Affecting kernel-debug package, versions *
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Test your applications- Snyk ID SNYK-RHEL8-KERNELDEBUG-7429116
- published 6 Jul 2024
- disclosed 5 Jul 2024
Introduced: 5 Jul 2024
CVE-2024-39479 Open this link in a new tabHow to fix?
There is no fixed version for RHEL:8 kernel-debug.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-debug package and not the kernel-debug package as distributed by RHEL.
See How to fix? for RHEL:8 relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
drm/i915/hwmon: Get rid of devm
When both hwmon and hwmon drvdata (on which hwmon depends) are device managed resources, the expectation, on device unbind, is that hwmon will be released before drvdata. However, in i915 there are two separate code paths, which both release either drvdata or hwmon and either can be released before the other. These code paths (for device unbind) are as follows (see also the bug referenced below):
Call Trace: release_nodes+0x11/0x70 devres_release_group+0xb2/0x110 component_unbind_all+0x8d/0xa0 component_del+0xa5/0x140 intel_pxp_tee_component_fini+0x29/0x40 [i915] intel_pxp_fini+0x33/0x80 [i915] i915_driver_remove+0x4c/0x120 [i915] i915_pci_remove+0x19/0x30 [i915] pci_device_remove+0x32/0xa0 device_release_driver_internal+0x19c/0x200 unbind_store+0x9c/0xb0
and
Call Trace: release_nodes+0x11/0x70 devres_release_all+0x8a/0xc0 device_unbind_cleanup+0x9/0x70 device_release_driver_internal+0x1c1/0x200 unbind_store+0x9c/0xb0
This means that in i915, if use devm, we cannot gurantee that hwmon will always be released before drvdata. Which means that we have a uaf if hwmon sysfs is accessed when drvdata has been released but hwmon hasn't.
The only way out of this seems to be do get rid of devm_ and release/free everything explicitly during device unbind.
v2: Change commit message and other minor code changes v3: Cleanup from i915_hwmon_register on error (Armin Wolf) v4: Eliminate potential static analyzer warning (Rodrigo) Eliminate fetch_and_zero (Jani) v5: Restore previous logic for ddat_gt->hwmon_dev error return (Andi)