Bug 2536376 (CVE-2026-93121)

Summary: CVE-2026-93121 kernel: usb: gadget: f_fs: Fix fence cleanup in ffs_dmabuf_transfer() error paths
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Doc Text:
A flaw was found in the Linux kernel's USB gadget function filesystem (f_fs) component. Specifically, an issue in the ffs_dmabuf_transfer() function's error handling can lead to undefined behavior. This occurs when a fence object is prematurely deallocated without proper initialization, potentially causing system instability or other unpredictable outcomes.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Description OSIDB Bzimport 2026-09-17 17:35:37 UTC 
In the Linux kernel, the following vulnerability has been resolved:

usb: gadget: f_fs: Fix fence cleanup in ffs_dmabuf_transfer() error paths

The error paths for endpoint-disabled (ESHUTDOWN) and request-allocation
failure (ENOMEM) in ffs_dmabuf_transfer() jump to err_fence_put which
calls dma_fence_put() on the fence. However, at that point the fence has
only been kmalloc'd — dma_fence_init() has not been called yet, so the
refcount and the fence ops are uninitialized. Calling dma_fence_put() on
such an object leads to undefined behavior.

Use kfree() instead, since the fence is just a plain allocation at this
stage, and rename the label to err_fence_free to reflect the actual
cleanup action.
Comment 1 gkamathe 2026-09-19 17:23:14 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-93121.mbox