On Thu, Jul 02, 2015 at 03:19:57PM +0300, Andrey Ryabinin wrote:
> Added:
> + if (total > count)
> + *(char *)0 = 0
>
> and never hit this condition.
>
OK, so it's definitely a mismatched response.
> req->tc->tag = tag-1;
> + if (WARN_ON(req->status != REQ_STATUS_IDLE))
> + pr_err("req->status: %d\n", req->status);
> req->status = REQ_STATUS_ALLOC;
>
> return req;
> [ 150.259076] 9pnet: req->status: 4
IOW, REQ_STATUS_RCVD. Hmm... Stray tag seen by req_done() after we'd already
freed the tag in question? That, or it really would have to had wrapped
around... Note that req_done() does *not* check anything about the req -
not even that p9_tag_lookup() hasn't returned NULL, so a server sending you
any response tagged with number well above anything you'd ever sent will
reliably oops you.
Frankly, the whole thing needs fuzzing from the server side - start throwing
crap at the client and see how badly does it get fucked... Folks, it's
a network protocol, with userland servers, no less. You *can't* assume
them competent and non-malicious...
How much traffic does it take to reproduce that fun, BTW? IOW, is attempting
to log the sequence of tag {allocation,freeing}/tag of packet being {sent,
received} something completely suicidal, or is it more or less feasible?
> I didn't get this. c->reqs[row] is always non-NULL as it should be, so this warning
> will trigger all the time.
????
row = (tag / P9_ROW_MAXTAG);
c->reqs[row] = kcalloc(P9_ROW_MAXTAG,
sizeof(struct p9_req_t), GFP_ATOMIC);
and you are seeing c->reqs[row] != NULL *BEFORE* that kcalloc()? All the time,
no less? Just to make sure we are on the same page - the delta against
mainline I would like tested is this:
diff --git a/net/9p/client.c b/net/9p/client.c
index 6f4c4c8..fa88c9a 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -248,6 +248,9 @@ p9_tag_alloc(struct p9_client *c, u16 tag, unsigned int max_size)
/* check again since original check was outside of lock */
while (tag >= c->max_tag) {
row = (tag / P9_ROW_MAXTAG);
+
+ WARN_ON_ONCE(c->reqs[row]); // are we about to leak?
+
c->reqs[row] = kcalloc(P9_ROW_MAXTAG,
sizeof(struct p9_req_t), GFP_ATOMIC);
@@ -286,6 +289,8 @@ p9_tag_alloc(struct p9_client *c, u16 tag, unsigned int max_size)
p9pdu_reset(req->rc);
req->tc->tag = tag-1;
+ if (req->status != REQ_STATUS_IDLE)
+ pr_err("using tag %d with odd status (%d)", tag, req->status);
req->status = REQ_STATUS_ALLOC;
return req;
@@ -425,6 +430,8 @@ void p9_client_cb(struct p9_client *c, struct p9_req_t *req, int status)
* the other thread wakes up will indeed be seen by the waiting side.
*/
smp_wmb();
+ if (req->status == REQ_STATUS_IDLE)
+ pr_err("late delivery, tag %d already freed", req->tc->tag);
req->status = status;
wake_up(req->wq);
@@ -693,6 +700,10 @@ static struct p9_req_t *p9_client_prepare_req(struct p9_client *c,
tag = p9_idpool_get(c->tagpool);
if (tag < 0)
return ERR_PTR(-ENOMEM);
+ if (WARN_ON_ONCE(tag != (u16)tag)) { // wrapped around?
+ p9_idpool_put(tag, c->tagpool);
+ return ERR_PTR(-ENOMEM);
+ }
}
req = p9_tag_alloc(c, tag, req_size);
@@ -1647,7 +1658,10 @@ p9_client_write(struct p9_fid *fid, u64 offset, struct iov_iter *from, int *err)
if (*err) {
trace_9p_protocol_dump(clnt, req->rc);
p9_free_req(clnt, req);
+ break;
}
+ if (rsize < count)
+ pr_err("mismatched reply [tag = %d]\n", req->tc->tag);
p9_debug(P9_DEBUG_9P, "<<< RWRITE count %d\n", count);
--
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