sunrpc: init gssp_lock before publishing proc entry

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-89540
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-11 20:19:37 UTC
Updated2026-09-11 20:19:37 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: sunrpc: init gssp_lock before publishing proc entry create_use_gss_proxy_proc_entry() publishes /proc/net/rpc/use-gss-proxy via proc_create_data() before init_gssp_clnt() runs mutex_init() on sn->gssp_lock. Once the dentry is linked under proc_subdir_lock it is immediately reachable from userspace, so a write that lands in the window drives set_gssp_clnt() into mutex_lock() on a zero-initialized struct mutex. create_use_gss_proxy_proc_entry(net) proc_create_data("use-gss-proxy", ...) /* dentry live */ init_gssp_clnt(sn) mutex_init(&sn->gssp_lock) /* too late */ write_gssp() set_gssp_clnt(net) mutex_lock(&sn->gssp_lock) /* uninitialized */ gssp_rpc_create(...) sn->gssp_clnt = clnt mutex_unlock(&sn->gssp_lock) The window spans only the two statements between proc_create_data() returning and init_gssp_clnt(), so a writer reaches it only if the registering thread is preempted there while another task is already opening the freshly published file. register_pernet_subsys() runs in preemptible context under pernet_ops_rwsem, so that preemption is possible, and the window widens on auth_rpcgss module load, when the proc entry is created for every live net namespace whose tasks are already running. A writer that wins the race locks a zero-filled struct mutex. On CONFIG_DEBUG_MUTEXES the missing magic value trips a "lock used without init" splat; on a production kernel the fast path acquires the lock via CMPXCHG(owner, 0, current). In the latter case a second writer that arrives before init_gssp_clnt() re-zeroes owner can enter set_gssp_clnt() concurrently, shut down the first writer's clnt while it is still in use, and leak the loser's clnt. Fix by initializing sn->gssp_lock in sunrpc_init_net() so its lifetime matches the sunrpc_net it lives in. sn->gssp_clnt is already NULL from the kzalloc that backs net_generic storage, so the lazy helper is no longer needed; drop init_gssp_clnt(), its prototype, and the call from create_use_gss_proxy_proc_entry(). sunrpc.ko is a build-time dependency of auth_rpcgss.ko, so sunrpc_init_net() has always run on every netns before any auth_gss pernet init can publish the proc entry.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 030d794bf49855f5e2a9e8dfbfad34211d1eb08b f15b87521168c2a92cb1931f532cba422f856f01 git Not specified
CNA Linux Linux affected 030d794bf49855f5e2a9e8dfbfad34211d1eb08b edeefb111d6181a4aa278f415b005efe284b9489 git Not specified
CNA Linux Linux affected 030d794bf49855f5e2a9e8dfbfad34211d1eb08b 3f019571928b269feebcff59926ec13294215e0e git Not specified
CNA Linux Linux affected 030d794bf49855f5e2a9e8dfbfad34211d1eb08b 5ce1ed6159731a41fdd0b03eedbed4e147036a5a git Not specified
CNA Linux Linux affected 3.10 Not specified
CNA Linux Linux unaffected 3.10 semver Not specified
CNA Linux Linux unaffected 6.12.109 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.50 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.4 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/5ce1ed6159731a41fdd0b03eedbed4e147036a5a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f15b87521168c2a92cb1931f532cba422f856f01 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/3f019571928b269feebcff59926ec13294215e0e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/edeefb111d6181a4aa278f415b005efe284b9489 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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