Bug 2422685 (CVE-2025-68185)

Summary: CVE-2025-68185 kernel: nfs4_setup_readdir(): insufficient locking for ->d_parent->d_inode dereferencing
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A race condition exists in the NFS4 client's nfs4_setup_readdir() function in the Linux kernel. The code dereferences ->d_parent->d_inode without holding d_lock, creating a theoretical race where the parent could be changed during the operation, leading to a null pointer dereference.
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Description OSIDB Bzimport 2025-12-16 14:03:40 UTC 
In the Linux kernel, the following vulnerability has been resolved:

nfs4_setup_readdir(): insufficient locking for ->d_parent->d_inode dereferencing

Theoretically it's an oopsable race, but I don't believe one can manage
to hit it on real hardware; might become doable on a KVM, but it still
won't be easy to attack.

Anyway, it's easy to deal with - since xdr_encode_hyper() is just a call of
put_unaligned_be64(), we can put that under ->d_lock and be done with that.
Comment 1 Alexander B 2025-12-17 03:06:15 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025121633-CVE-2025-68185-6db0@gregkh/T