Wind River Support Network

Description

In the Linux kernel, the following vulnerability has been resolved:  nstree: check listing permission before taking a namespace reference  legitimize_ns() takes a reference on the candidate namespace before may_list_ns() has decided whether the caller may see it. The __free(ns_put) cleanup on the denied path can drop the last reference to a mount namespace while we still hold the rcu read lock, and put_mnt_ns() may sleep there. This is the same problem commit 2ec2aff3c8e2 ("ns: make sure reference are dropped outside of rcu lock") fixed for the put_user() path. Neither ns_requested() nor may_list_ns() needs a reference, both only look at the namespace type and at the caller's own namespaces, so do the checks first and take the reference last.  Splat:    Voluntary context switch within RCU read-side critical section!   WARNING: kernel/rcu/tree_plugin.h:332 at rcu_note_context_switch+0x238/0x2a0, CPU#5: a/3442   CPU: 5 UID: 1000 PID: 3442 Comm: a Not tainted 7.0.0-30-generic #30-Ubuntu PREEMPT(lazy)   RIP: 0010:rcu_note_context_switch+0x238/0x2a0   Call Trace:    <TASK>    __schedule+0xcf/0x650    schedule+0x27/0x90    schedule_preempt_disabled+0x15/0x30    __mutex_lock.constprop.0+0x550/0xaf0    __mutex_lock_slowpath+0x13/0x20    mutex_lock+0x3b/0x50    exp_funnel_lock+0xb2/0x260    synchronize_rcu_expedited+0xe7/0x220    namespace_unlock+0x26a/0x320    put_mnt_ns+0xd3/0x120    mntns_put+0xe/0x20    do_listns+0x13e/0x560    __do_sys_listns+0x126/0x2d0    __x64_sys_listns+0x20/0x30    x64_sys_call+0x2366/0x2390    do_syscall_64+0x105/0x5a0    entry_SYSCALL_64_after_hwframe+0x76/0x7e    </TASK>
Data source: kernel.org (416baaa9-dc9f-4396-8d5f-8c081fb06d67)