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Subject[PATCH 4.9 14/78] act_ife: fix a potential deadlock
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Cong Wang <xiyou.wangcong@gmail.com>

[ Upstream commit 5ffe57da29b3802baeddaa40909682bbb4cb4d48 ]

use_all_metadata() acquires read_lock(&ife_mod_lock), then calls
add_metainfo() which calls find_ife_oplist() which acquires the same
lock again. Deadlock!

Introduce __add_metainfo() which accepts struct tcf_meta_ops *ops
as an additional parameter and let its callers to decide how
to find it. For use_all_metadata(), it already has ops, no
need to find it again, just call __add_metainfo() directly.

And, as ife_mod_lock is only needed for find_ife_oplist(),
this means we can make non-atomic allocation for populate_metalist()
now.

Fixes: 817e9f2c5c26 ("act_ife: acquire ife_mod_lock before reading ifeoplist")
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sched/act_ife.c | 34 +++++++++++++++++++++-------------
1 file changed, 21 insertions(+), 13 deletions(-)

--- a/net/sched/act_ife.c
+++ b/net/sched/act_ife.c
@@ -296,22 +296,16 @@ static int load_metaops_and_vet(u32 meta

/* called when adding new meta information
*/
-static int add_metainfo(struct tcf_ife_info *ife, u32 metaid, void *metaval,
- int len, bool atomic, bool exists)
+static int __add_metainfo(const struct tcf_meta_ops *ops,
+ struct tcf_ife_info *ife, u32 metaid, void *metaval,
+ int len, bool atomic, bool exists)
{
struct tcf_meta_info *mi = NULL;
- struct tcf_meta_ops *ops = find_ife_oplist(metaid);
int ret = 0;

- if (!ops)
- return -ENOENT;
-
mi = kzalloc(sizeof(*mi), atomic ? GFP_ATOMIC : GFP_KERNEL);
- if (!mi) {
- /*put back what find_ife_oplist took */
- module_put(ops->owner);
+ if (!mi)
return -ENOMEM;
- }

mi->metaid = metaid;
mi->ops = ops;
@@ -319,7 +313,6 @@ static int add_metainfo(struct tcf_ife_i
ret = ops->alloc(mi, metaval, atomic ? GFP_ATOMIC : GFP_KERNEL);
if (ret != 0) {
kfree(mi);
- module_put(ops->owner);
return ret;
}
}
@@ -333,6 +326,21 @@ static int add_metainfo(struct tcf_ife_i
return ret;
}

+static int add_metainfo(struct tcf_ife_info *ife, u32 metaid, void *metaval,
+ int len, bool exists)
+{
+ const struct tcf_meta_ops *ops = find_ife_oplist(metaid);
+ int ret;
+
+ if (!ops)
+ return -ENOENT;
+ ret = __add_metainfo(ops, ife, metaid, metaval, len, false, exists);
+ if (ret)
+ /*put back what find_ife_oplist took */
+ module_put(ops->owner);
+ return ret;
+}
+
static int use_all_metadata(struct tcf_ife_info *ife, bool exists)
{
struct tcf_meta_ops *o;
@@ -341,7 +349,7 @@ static int use_all_metadata(struct tcf_i

read_lock(&ife_mod_lock);
list_for_each_entry(o, &ifeoplist, list) {
- rc = add_metainfo(ife, o->metaid, NULL, 0, true, exists);
+ rc = __add_metainfo(o, ife, o->metaid, NULL, 0, true, exists);
if (rc == 0)
installed += 1;
}
@@ -430,7 +438,7 @@ static int populate_metalist(struct tcf_
if (rc != 0)
return rc;

- rc = add_metainfo(ife, i, val, len, false, exists);
+ rc = add_metainfo(ife, i, val, len, exists);
if (rc)
return rc;
}

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