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authorEric W. Biederman <ebiederm@xmission.com>2022-01-24 12:46:50 -0600
committerEric W. Biederman <ebiederm@xmission.com>2022-01-26 18:34:11 -0600
commitf9d87929d451d3e649699d0f1d74f71f77ad38f5 (patch)
tree89237016732d74ce6b40294164c716e5723fd4e3
parente783362eb54cd99b2cac8b3a9aeac942e6f6ac07 (diff)
ucount: Make get_ucount a safe get_user replacement
When the ucount code was refactored to create get_ucount it was missed that some of the contexts in which a rlimit is kept elevated can be the only reference to the user/ucount in the system. Ordinary ucount references exist in places that also have a reference to the user namspace, but in POSIX message queues, the SysV shm code, and the SIGPENDING code there is no independent user namespace reference. Inspection of the the user_namespace show no instance of circular references between struct ucounts and the user_namespace. So hold a reference from struct ucount to i's user_namespace to resolve this problem. Link: https://lore.kernel.org/lkml/YZV7Z+yXbsx9p3JN@fixkernel.com/ Reported-by: Qian Cai <quic_qiancai@quicinc.com> Reported-by: Mathias Krause <minipli@grsecurity.net> Tested-by: Mathias Krause <minipli@grsecurity.net> Reviewed-by: Mathias Krause <minipli@grsecurity.net> Reviewed-by: Alexey Gladkov <legion@kernel.org> Fixes: d64696905554 ("Reimplement RLIMIT_SIGPENDING on top of ucounts") Fixes: 6e52a9f0532f ("Reimplement RLIMIT_MSGQUEUE on top of ucounts") Fixes: d7c9e99aee48 ("Reimplement RLIMIT_MEMLOCK on top of ucounts") Cc: stable@vger.kernel.org Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
-rw-r--r--kernel/ucount.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/ucount.c b/kernel/ucount.c
index 7b32c356ebc5..65b597431c86 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -190,6 +190,7 @@ struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid)
kfree(new);
} else {
hlist_add_head(&new->node, hashent);
+ get_user_ns(new->ns);
spin_unlock_irq(&ucounts_lock);
return new;
}
@@ -210,6 +211,7 @@ void put_ucounts(struct ucounts *ucounts)
if (atomic_dec_and_lock_irqsave(&ucounts->count, &ucounts_lock, flags)) {
hlist_del_init(&ucounts->node);
spin_unlock_irqrestore(&ucounts_lock, flags);
+ put_user_ns(ucounts->ns);
kfree(ucounts);
}
}