nfsd: add missing read barrier to rpc_status_get dumpit seqcount retry

Summary

In the Linux kernel, the following vulnerability has been resolved: nfsd: add missing read barrier to rpc_status_get dumpit seqcount retry The hand-rolled seqcount-like protocol in nfsd_nl_rpc_status_get_dumpit() is missing a read memory barrier (smp_rmb) before its second counter check. The standard kernel read_seqcount_retry() includes smp_rmb() to ensure that all data reads complete before the counter is re-checked. Without this barrier, on weakly-ordered architectures (ARM, POWER), the CPU may reorder field reads past the second counter check, making the retry logic ineffective: it could observe a consistent counter pair while reading fields that have been concurrently modified by the writer. Add smp_rmb() before the second counter check to order the field reads ahead of it, matching the barrier semantics of the standard seqcount read-side. The begin-side smp_load_acquire() already pairs with the smp_store_release() in nfsd_dispatch(); with the smp_rmb() now ordering the field reads, the retry check no longer needs acquire semantics and reads the counter with a plain READ_ONCE(), as read_seqcount_retry() does. [ cel: Use READ_ONCE instead of smp_load_acquire() ]

Timeline

1. Sep 24, 2026, 3:29 PM UTCCVE published
2. Oct 19, 2026, 9:07 AM UTCRecord last updated

Affected versions

• Linux Linux

  From bd9d6a3efa9709e653aafbeb859289feccb8e70c · fixed in f501f2f4ec1d2dfe39e21c98630314074a9b30b0; From bd9d6a3efa9709e653aafbeb859289feccb8e70c · fixed in 1aea0482b98ecd7d0249204665f2ad4ad517f66b; From bd9d6a3efa9709e653aafbeb859289feccb8e70c · fixed in 9b5f6475006cd8e3b5b99b8eb3cd74dbb1ce9df8; From bd9d6a3efa9709e653aafbeb859289feccb8e70c · fixed in a71f161a857117e8e0264deb7d14fff5c98adcf5

• Linux Linux

  6.7

• KernelLinux

  From 6.7.0 · fixed in 6.12.109; From 6.13.0 · fixed in 6.18.50; From 6.19.0 · fixed in 7.2.4

References 4