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CVE-2026-89540

sunrpc: init gssp_lock before publishing proc entry

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: total

Summary

In 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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From 030d794bf49855f5e2a9e8dfbfad34211d1eb08b · fixed in 159a4fab7170badd6c4a553aef81cac079d6f4ee; From 030d794bf49855f5e2a9e8dfbfad34211d1eb08b · fixed in b3526ae3351968f6726bcbe25d8d09973ad79109; From 030d794bf49855f5e2a9e8dfbfad34211d1eb08b · fixed in 7f5bcdc8da15077ebe846c2756a5a17741021410; From 030d794bf49855f5e2a9e8dfbfad34211d1eb08b · fixed in 89c8e0733e8c46b7973503f15b1b31a8587d8030; From 030d794bf49855f5e2a9e8dfbfad34211d1eb08b · fixed in f15b87521168c2a92cb1931f532cba422f856f01; From 030d794bf49855f5e2a9e8dfbfad34211d1eb08b · fixed in edeefb111d6181a4aa278f415b005efe284b9489; From 030d794bf49855f5e2a9e8dfbfad34211d1eb08b · fixed in 3f019571928b269feebcff59926ec13294215e0e; From 030d794bf49855f5e2a9e8dfbfad34211d1eb08b · fixed in 5ce1ed6159731a41fdd0b03eedbed4e147036a5a

  • Linux Linux

    3.10

  • KernelLinux

    From 3.10.0 · fixed in 5.10.270; From 5.11.0 · fixed in 5.15.221; From 5.16.0 · fixed in 6.1.188; From 6.2.0 · fixed in 6.6.157; 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 8

git.kernel.org