[SRU E/F/focal:linux-oem-5.6 1/2] cgroup: fix cgroup_sk_alloc() for sk_clone_lock()
Thadeu Lima de Souza Cascardo
cascardo at canonical.com
Mon Jul 27 13:28:40 UTC 2020
From: Cong Wang <xiyou.wangcong at gmail.com>
BugLink: https://bugs.launchpad.net/bugs/1886860
When we clone a socket in sk_clone_lock(), its sk_cgrp_data is
copied, so the cgroup refcnt must be taken too. And, unlike the
sk_alloc() path, sock_update_netprioidx() is not called here.
Therefore, it is safe and necessary to grab the cgroup refcnt
even when cgroup_sk_alloc is disabled.
sk_clone_lock() is in BH context anyway, the in_interrupt()
would terminate this function if called there. And for sk_alloc()
skcd->val is always zero. So it's safe to factor out the code
to make it more readable.
The global variable 'cgroup_sk_alloc_disabled' is used to determine
whether to take these reference counts. It is impossible to make
the reference counting correct unless we save this bit of information
in skcd->val. So, add a new bit there to record whether the socket
has already taken the reference counts. This obviously relies on
kmalloc() to align cgroup pointers to at least 4 bytes,
ARCH_KMALLOC_MINALIGN is certainly larger than that.
This bug seems to be introduced since the beginning, commit
d979a39d7242 ("cgroup: duplicate cgroup reference when cloning sockets")
tried to fix it but not compeletely. It seems not easy to trigger until
the recent commit 090e28b229af
("netprio_cgroup: Fix unlimited memory leak of v2 cgroups") was merged.
Fixes: bd1060a1d671 ("sock, cgroup: add sock->sk_cgroup")
Reported-by: Cameron Berkenpas <cam at neo-zeon.de>
Reported-by: Peter Geis <pgwipeout at gmail.com>
Reported-by: Lu Fengqi <lufq.fnst at cn.fujitsu.com>
Reported-by: Daniël Sonck <dsonck92 at gmail.com>
Reported-by: Zhang Qiang <qiang.zhang at windriver.com>
Tested-by: Cameron Berkenpas <cam at neo-zeon.de>
Tested-by: Peter Geis <pgwipeout at gmail.com>
Tested-by: Thomas Lamprecht <t.lamprecht at proxmox.com>
Cc: Daniel Borkmann <daniel at iogearbox.net>
Cc: Zefan Li <lizefan at huawei.com>
Cc: Tejun Heo <tj at kernel.org>
Cc: Roman Gushchin <guro at fb.com>
Signed-off-by: Cong Wang <xiyou.wangcong at gmail.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(cherry picked from commit ad0f75e5f57ccbceec13274e1e242f2b5a6397ed)
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo at canonical.com>
---
include/linux/cgroup-defs.h | 6 ++++--
include/linux/cgroup.h | 4 +++-
kernel/cgroup/cgroup.c | 31 +++++++++++++++++++------------
net/core/sock.c | 2 +-
4 files changed, 27 insertions(+), 16 deletions(-)
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 430e219e3aba..2ebacb7ef501 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -797,7 +797,8 @@ struct sock_cgroup_data {
union {
#ifdef __LITTLE_ENDIAN
struct {
- u8 is_data;
+ u8 is_data : 1;
+ u8 no_refcnt : 1;
u8 padding;
u16 prioidx;
u32 classid;
@@ -807,7 +808,8 @@ struct sock_cgroup_data {
u32 classid;
u16 prioidx;
u8 padding;
- u8 is_data;
+ u8 no_refcnt : 1;
+ u8 is_data : 1;
} __packed;
#endif
u64 val;
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 57577075d204..202852383ae9 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -822,6 +822,7 @@ extern spinlock_t cgroup_sk_update_lock;
void cgroup_sk_alloc_disable(void);
void cgroup_sk_alloc(struct sock_cgroup_data *skcd);
+void cgroup_sk_clone(struct sock_cgroup_data *skcd);
void cgroup_sk_free(struct sock_cgroup_data *skcd);
static inline struct cgroup *sock_cgroup_ptr(struct sock_cgroup_data *skcd)
@@ -835,7 +836,7 @@ static inline struct cgroup *sock_cgroup_ptr(struct sock_cgroup_data *skcd)
*/
v = READ_ONCE(skcd->val);
- if (v & 1)
+ if (v & 3)
return &cgrp_dfl_root.cgrp;
return (struct cgroup *)(unsigned long)v ?: &cgrp_dfl_root.cgrp;
@@ -847,6 +848,7 @@ static inline struct cgroup *sock_cgroup_ptr(struct sock_cgroup_data *skcd)
#else /* CONFIG_CGROUP_DATA */
static inline void cgroup_sk_alloc(struct sock_cgroup_data *skcd) {}
+static inline void cgroup_sk_clone(struct sock_cgroup_data *skcd) {}
static inline void cgroup_sk_free(struct sock_cgroup_data *skcd) {}
#endif /* CONFIG_CGROUP_DATA */
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 7c9e97553a00..35faf082a709 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -6379,18 +6379,8 @@ void cgroup_sk_alloc_disable(void)
void cgroup_sk_alloc(struct sock_cgroup_data *skcd)
{
- if (cgroup_sk_alloc_disabled)
- return;
-
- /* Socket clone path */
- if (skcd->val) {
- /*
- * We might be cloning a socket which is left in an empty
- * cgroup and the cgroup might have already been rmdir'd.
- * Don't use cgroup_get_live().
- */
- cgroup_get(sock_cgroup_ptr(skcd));
- cgroup_bpf_get(sock_cgroup_ptr(skcd));
+ if (cgroup_sk_alloc_disabled) {
+ skcd->no_refcnt = 1;
return;
}
@@ -6415,10 +6405,27 @@ void cgroup_sk_alloc(struct sock_cgroup_data *skcd)
rcu_read_unlock();
}
+void cgroup_sk_clone(struct sock_cgroup_data *skcd)
+{
+ if (skcd->val) {
+ if (skcd->no_refcnt)
+ return;
+ /*
+ * We might be cloning a socket which is left in an empty
+ * cgroup and the cgroup might have already been rmdir'd.
+ * Don't use cgroup_get_live().
+ */
+ cgroup_get(sock_cgroup_ptr(skcd));
+ cgroup_bpf_get(sock_cgroup_ptr(skcd));
+ }
+}
+
void cgroup_sk_free(struct sock_cgroup_data *skcd)
{
struct cgroup *cgrp = sock_cgroup_ptr(skcd);
+ if (skcd->no_refcnt)
+ return;
cgroup_bpf_put(cgrp);
cgroup_put(cgrp);
}
diff --git a/net/core/sock.c b/net/core/sock.c
index 0adf7a9e5a90..6ef468767ab0 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1836,7 +1836,7 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
/* sk->sk_memcg will be populated at accept() time */
newsk->sk_memcg = NULL;
- cgroup_sk_alloc(&newsk->sk_cgrp_data);
+ cgroup_sk_clone(&newsk->sk_cgrp_data);
rcu_read_lock();
filter = rcu_dereference(sk->sk_filter);
--
2.25.1
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