Bug 2461468 (CVE-2026-31535)

Summary: CVE-2026-31535 kernel: smb: client: make use of smbdirect_socket.recv_io.credits.available
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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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A flaw was found in the Linux kernel. A race condition exists in the SMB client's receive credit management, specifically in how `smbdirect_socket.recv_io.credits.available` are handled. This could lead to incorrect credit allocation, potentially causing instability or unexpected behavior within the system.
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Description OSIDB Bzimport 2026-04-24 15:03:12 UTC 
In the Linux kernel, the following vulnerability has been resolved:

smb: client: make use of smbdirect_socket.recv_io.credits.available

The logic off managing recv credits by counting posted recv_io and
granted credits is racy.

That's because the peer might already consumed a credit,
but between receiving the incoming recv at the hardware
and processing the completion in the 'recv_done' functions
we likely have a window where we grant credits, which
don't really exist.

So we better have a decicated counter for the
available credits, which will be incremented
when we posted new recv buffers and drained when
we grant the credits to the peer.
Comment 1 Keith Grant 2026-04-24 16:24:05 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026042433-CVE-2026-31535-1c83@gregkh/T