Bug 2320595 (CVE-2024-50043)

Summary: CVE-2024-50043 kernel: nfsd: fix possible badness in FREE_STATEID
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedCC: dfreiber, drow, jburrell, vkumar
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Hardware: All   
OS: Linux   
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Bug Depends On: 2320923    
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Description OSIDB Bzimport 2024-10-21 20:02:05 UTC 
In the Linux kernel, the following vulnerability has been resolved:

nfsd: fix possible badness in FREE_STATEID

When multiple FREE_STATEIDs are sent for the same delegation stateid,
it can lead to a possible either use-after-free or counter refcount
underflow errors.

In nfsd4_free_stateid() under the client lock we find a delegation
stateid, however the code drops the lock before calling nfs4_put_stid(),
that allows another FREE_STATE to find the stateid again. The first one
will proceed to then free the stateid which leads to either
use-after-free or decrementing already zeroed counter.
Comment 1 Avinash Hanwate 2024-10-22 11:19:33 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2024102133-CVE-2024-50043-86f8@gregkh/T