lkml.org 
[lkml]   [2022]   [Jan]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 5.16 024/200] ucount: Make get_ucount a safe get_user replacement
Date
From: Eric W. Biederman <ebiederm@xmission.com>

commit f9d87929d451d3e649699d0f1d74f71f77ad38f5 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/ucount.c | 2 ++
1 file changed, 2 insertions(+)

--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -190,6 +190,7 @@ struct ucounts *alloc_ucounts(struct use
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);
}
}

\
 
 \ /
  Last update: 2022-01-31 12:41    [W:2.986 / U:0.700 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site