Bug 2507071 (CVE-2026-64327)

Summary: CVE-2026-64327 kernel: usb: gadget: f_fs: Initialize epfile->in early to fix endpoint direction checks
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: rhel-process-autobot, 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 FunctionFS (f_fs) module, which handles USB gadget functionality. This vulnerability occurs because the endpoint direction (`epfile->in`) was not correctly initialized until a USB host connected. Consequently, early operations initiated by userspace programs could encounter incorrect data transfer directions, potentially leading to unintended data access or corruption.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-07-25 10:03:28 UTC 
In the Linux kernel, the following vulnerability has been resolved:

usb: gadget: f_fs: Initialize epfile->in early to fix endpoint direction checks

When parsing endpoint descriptors, ffs_data_got_descs() generates the
eps_addrmap which contains the endpoint direction. However, epfile->in
was previously only populated in ffs_func_eps_enable() which executes
upon USB host connection. As a result, early userspace ioctls like
FUNCTIONFS_DMABUF_ATTACH that run before the host connects would see
epfile->in as 0, leading to incorrect DMA directions.

By moving the initialization to ffs_epfiles_create(), epfile->in is
accurate before userspace opens the endpoint files.
Comment 1 TEJ RATHI 2026-07-30 05:42:34 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026072512-CVE-2026-64327-fb4d@gregkh/T