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https://github.com/Divested-Mobile/DivestOS-Build.git
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141 lines
4.3 KiB
Diff
141 lines
4.3 KiB
Diff
From 712f4aad406bb1ed67f3f98d04c044191f0ff593 Mon Sep 17 00:00:00 2001
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From: willy tarreau <w@1wt.eu>
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Date: Sun, 10 Jan 2016 07:54:56 +0100
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Subject: unix: properly account for FDs passed over unix sockets
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It is possible for a process to allocate and accumulate far more FDs than
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the process' limit by sending them over a unix socket then closing them
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to keep the process' fd count low.
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This change addresses this problem by keeping track of the number of FDs
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in flight per user and preventing non-privileged processes from having
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more FDs in flight than their configured FD limit.
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Reported-by: socketpair@gmail.com
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Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
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Mitigates: CVE-2013-4312 (Linux 2.0+)
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Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
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Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
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Signed-off-by: Willy Tarreau <w@1wt.eu>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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include/linux/sched.h | 1 +
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net/unix/af_unix.c | 24 ++++++++++++++++++++----
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net/unix/garbage.c | 13 ++++++++-----
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3 files changed, 29 insertions(+), 9 deletions(-)
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diff --git a/include/linux/sched.h b/include/linux/sched.h
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index edad7a4..fbf25f1 100644
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--- a/include/linux/sched.h
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+++ b/include/linux/sched.h
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@@ -830,6 +830,7 @@ struct user_struct {
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unsigned long mq_bytes; /* How many bytes can be allocated to mqueue? */
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#endif
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unsigned long locked_shm; /* How many pages of mlocked shm ? */
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+ unsigned long unix_inflight; /* How many files in flight in unix sockets */
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#ifdef CONFIG_KEYS
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struct key *uid_keyring; /* UID specific keyring */
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diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
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index ef05cd9..e3f85bc 100644
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--- a/net/unix/af_unix.c
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+++ b/net/unix/af_unix.c
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@@ -1513,6 +1513,21 @@ static void unix_destruct_scm(struct sk_buff *skb)
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sock_wfree(skb);
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}
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+/*
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+ * The "user->unix_inflight" variable is protected by the garbage
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+ * collection lock, and we just read it locklessly here. If you go
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+ * over the limit, there might be a tiny race in actually noticing
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+ * it across threads. Tough.
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+ */
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+static inline bool too_many_unix_fds(struct task_struct *p)
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+{
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+ struct user_struct *user = current_user();
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+
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+ if (unlikely(user->unix_inflight > task_rlimit(p, RLIMIT_NOFILE)))
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+ return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
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+ return false;
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+}
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+
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#define MAX_RECURSION_LEVEL 4
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static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
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@@ -1521,6 +1536,9 @@ static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
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unsigned char max_level = 0;
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int unix_sock_count = 0;
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+ if (too_many_unix_fds(current))
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+ return -ETOOMANYREFS;
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+
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for (i = scm->fp->count - 1; i >= 0; i--) {
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struct sock *sk = unix_get_socket(scm->fp->fp[i]);
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@@ -1542,10 +1560,8 @@ static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
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if (!UNIXCB(skb).fp)
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return -ENOMEM;
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- if (unix_sock_count) {
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- for (i = scm->fp->count - 1; i >= 0; i--)
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- unix_inflight(scm->fp->fp[i]);
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- }
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+ for (i = scm->fp->count - 1; i >= 0; i--)
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+ unix_inflight(scm->fp->fp[i]);
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return max_level;
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}
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diff --git a/net/unix/garbage.c b/net/unix/garbage.c
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index a73a226..8fcdc22 100644
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--- a/net/unix/garbage.c
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+++ b/net/unix/garbage.c
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@@ -120,11 +120,11 @@ void unix_inflight(struct file *fp)
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{
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struct sock *s = unix_get_socket(fp);
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+ spin_lock(&unix_gc_lock);
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+
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if (s) {
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struct unix_sock *u = unix_sk(s);
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- spin_lock(&unix_gc_lock);
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-
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if (atomic_long_inc_return(&u->inflight) == 1) {
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BUG_ON(!list_empty(&u->link));
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list_add_tail(&u->link, &gc_inflight_list);
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@@ -132,25 +132,28 @@ void unix_inflight(struct file *fp)
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BUG_ON(list_empty(&u->link));
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}
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unix_tot_inflight++;
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- spin_unlock(&unix_gc_lock);
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}
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+ fp->f_cred->user->unix_inflight++;
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+ spin_unlock(&unix_gc_lock);
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}
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void unix_notinflight(struct file *fp)
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{
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struct sock *s = unix_get_socket(fp);
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+ spin_lock(&unix_gc_lock);
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+
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if (s) {
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struct unix_sock *u = unix_sk(s);
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- spin_lock(&unix_gc_lock);
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BUG_ON(list_empty(&u->link));
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if (atomic_long_dec_and_test(&u->inflight))
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list_del_init(&u->link);
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unix_tot_inflight--;
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- spin_unlock(&unix_gc_lock);
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}
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+ fp->f_cred->user->unix_inflight--;
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+ spin_unlock(&unix_gc_lock);
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}
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static void scan_inflight(struct sock *x, void (*func)(struct unix_sock *),
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--
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cgit v1.1
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