@@ -94,6 +94,7 @@ struct p9_req_t {
* @trans: tranport instance state and API
* @fids: All active FID handles
* @reqs: All active requests.
+ * @idr_lock: protect @fids and @reqs when modifying IDR
* @name: node name used as client id
*
* The client structure is used to keep track of various per-client
@@ -122,6 +123,7 @@ struct p9_client {
struct idr fids;
struct idr reqs;
+ spinlock_t idr_lock;
char name[__NEW_UTS_LEN + 1];
};
@@ -283,14 +283,14 @@ p9_tag_alloc(struct p9_client *c, int8_t type, unsigned int max_size)
INIT_LIST_HEAD(&req->req_list);
idr_preload(GFP_NOFS);
- spin_lock_irq(&c->lock);
+ spin_lock_irq(&c->idr_lock);
if (type == P9_TVERSION)
tag = idr_alloc(&c->reqs, req, P9_NOTAG, P9_NOTAG + 1,
GFP_NOWAIT);
else
tag = idr_alloc(&c->reqs, req, 0, P9_NOTAG, GFP_NOWAIT);
req->tc.tag = tag;
- spin_unlock_irq(&c->lock);
+ spin_unlock_irq(&c->idr_lock);
idr_preload_end();
if (tag < 0)
goto free;
@@ -364,9 +364,9 @@ static void p9_tag_remove(struct p9_client *c, struct p9_req_t *r)
u16 tag = r->tc.tag;
p9_debug(P9_DEBUG_MUX, "freeing clnt %p req %p tag: %d\n", c, r, tag);
- spin_lock_irqsave(&c->lock, flags);
+ spin_lock_irqsave(&c->idr_lock, flags);
idr_remove(&c->reqs, tag);
- spin_unlock_irqrestore(&c->lock, flags);
+ spin_unlock_irqrestore(&c->idr_lock, flags);
}
int p9_req_put(struct p9_client *c, struct p9_req_t *r)
@@ -813,10 +813,10 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt)
refcount_set(&fid->count, 1);
idr_preload(GFP_KERNEL);
- spin_lock_irq(&clnt->lock);
+ spin_lock_irq(&clnt->idr_lock);
ret = idr_alloc_u32(&clnt->fids, fid, &fid->fid, P9_NOFID - 1,
GFP_NOWAIT);
- spin_unlock_irq(&clnt->lock);
+ spin_unlock_irq(&clnt->idr_lock);
idr_preload_end();
if (!ret) {
trace_9p_fid_ref(fid, P9_FID_REF_CREATE);
@@ -835,9 +835,9 @@ static void p9_fid_destroy(struct p9_fid *fid)
p9_debug(P9_DEBUG_FID, "fid %d\n", fid->fid);
trace_9p_fid_ref(fid, P9_FID_REF_DESTROY);
clnt = fid->clnt;
- spin_lock_irqsave(&clnt->lock, flags);
+ spin_lock_irqsave(&clnt->idr_lock, flags);
idr_remove(&clnt->fids, fid->fid);
- spin_unlock_irqrestore(&clnt->lock, flags);
+ spin_unlock_irqrestore(&clnt->idr_lock, flags);
kfree(fid->rdir);
kfree(fid);
}
@@ -943,6 +943,7 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
memcpy(clnt->name, client_id, strlen(client_id) + 1);
spin_lock_init(&clnt->lock);
+ spin_lock_init(&clnt->idr_lock);
idr_init(&clnt->fids);
idr_init(&clnt->reqs);
syzbot is reporting inconsistent lock state in p9_req_put(), for p9_tag_remove() from p9_req_put() from IRQ context is using spin_lock_irqsave() on "struct p9_client"->lock but other locations not from IRQ context are using spin_lock(). Since spin_lock() => spin_lock_irqsave() conversion on this lock will needlessly disable IRQ for infrequent event, and p9_tag_remove() needs to disable IRQ only for modifying IDR (RCU read lock can be used for reading IDR), let's introduce a spinlock dedicated for serializing idr_alloc()/idr_alloc_u32()/idr_remove() calls. Since this spinlock will be held as innermost lock, circular locking dependency problem won't happen by adding this spinlock. Link: https://syzkaller.appspot.com/bug?extid=2f20b523930c32c160cc [1] Reported-by: syzbot <syzbot+2f20b523930c32c160cc@syzkaller.appspotmail.com> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> --- Changes in v2: Make this spinlock per "struct p9_client", though I don't know how we should update "@lock" when "@idr_lock" also protects @fids and @reqs... /** * struct p9_client - per client instance state * @lock: protect @fids and @reqs * @msize: maximum data size negotiated by protocol * @proto_version: 9P protocol version to use * @trans_mod: module API instantiated with this client * @status: connection state * @trans: tranport instance state and API * @fids: All active FID handles * @reqs: All active requests. + * @idr_lock: protect @fids and @reqs when modifying IDR * @name: node name used as client id * * The client structure is used to keep track of various per-client * state that has been instantiated. */ include/net/9p/client.h | 2 ++ net/9p/client.c | 17 +++++++++-------- 2 files changed, 11 insertions(+), 8 deletions(-)