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| author | Eric W. Biederman <ebiederm@xmission.com> | 2022-01-24 12:46:50 -0600 |
|---|---|---|
| committer | Eric W. Biederman <ebiederm@xmission.com> | 2022-01-26 18:34:11 -0600 |
| commit | f9d87929d451d3e649699d0f1d74f71f77ad38f5 (patch) | |
| tree | 89237016732d74ce6b40294164c716e5723fd4e3 /kernel/ucount.c | |
| parent | e783362eb54cd99b2cac8b3a9aeac942e6f6ac07 (diff) | |
| download | lwn-f9d87929d451d3e649699d0f1d74f71f77ad38f5.tar.gz lwn-f9d87929d451d3e649699d0f1d74f71f77ad38f5.zip | |
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>
Diffstat (limited to 'kernel/ucount.c')
| -rw-r--r-- | kernel/ucount.c | 2 |
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); } } |