[PATCH 1/2] 9p: client_create/destroy: only call trans_mod->close after create

[PATCH 1/2] 9p: client_create/destroy: only call trans_mod->close after create

[Dominique Martinet]

destroy code would incorrectly call close() if trans_mod exists after some
hasty code cleanup: we need to make sure we only call close after create

The new bool added to track this has been added in a hole of the struct
and will not increase p9_client's size.
It might be possible to do better with a bit more work, but that will
have to do for now.

Link: https://lkml.kernel.org/r/00000000000015ac7905e97ebaed@google.com
Reported-by: syzbot+67d13108d855f451cafc@syzkaller.appspotmail.com
Reported-by: Leon Romanovsky <leon@kernel.org>
Fixes: 3ff51294a055 ("9p: p9_client_create: use p9_client_destroy on failure")
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
---
v4: start over from scratch with a pool to properly track initialization
state instead of kludging over clnt->trans itself which is "private" to
the trans

 include/net/9p/client.h | 2 ++
 net/9p/client.c         | 3 ++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/net/9p/client.h b/include/net/9p/client.h
index 78ebcf782ce5..3f7f473da05a 100644
--- a/include/net/9p/client.h
+++ b/include/net/9p/client.h
@@ -89,6 +89,7 @@ struct p9_req_t {
  * @lock: protect @fids and @reqs
  * @msize: maximum data size negotiated by protocol
  * @proto_version: 9P protocol version to use
+ * @trans_initialized: Whether transport's close() is safe to call
  * @trans_mod: module API instantiated with this client
  * @status: connection state
  * @trans: tranport instance state and API
@@ -103,6 +104,7 @@ struct p9_client {
 	spinlock_t lock;
 	unsigned int msize;
 	unsigned char proto_version;
+	bool trans_initialized;
 	struct p9_trans_module *trans_mod;
 	enum p9_trans_status status;
 	void *trans;
diff --git a/net/9p/client.c b/net/9p/client.c
index bfa80f01992e..cf2d5b60b61b 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -992,6 +992,7 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
 	err = clnt->trans_mod->create(clnt, dev_name, options);
 	if (err)
 		goto out;
+	clnt->trans_initialized = true;
 
 	if (clnt->msize > clnt->trans_mod->maxsize) {
 		clnt->msize = clnt->trans_mod->maxsize;
@@ -1036,7 +1037,7 @@ void p9_client_destroy(struct p9_client *clnt)
 
 	p9_debug(P9_DEBUG_MUX, "clnt %p\n", clnt);
 
-	if (clnt->trans_mod)
+	if (clnt->trans_mod && clnt->trans_initialized)
 		clnt->trans_mod->close(clnt);
 
 	v9fs_put_trans(clnt->trans_mod);
-- 
2.35.1

[PATCH 2/2] 9p: avoid double put_trans on parse_opt failure

[Dominique Martinet]

p9_client_destroy will catch that trans and put it when p9_client_create fails

This was brought up when reviewing an alternative implementation of the
previous patch [1]

Link: https://lkml.kernel.org/r/YzVzjR4Yz3Oo3JS+@codewreck.org [1]
Fixes: 3ff51294a055 ("9p: p9_client_create: use p9_client_destroy on failure")
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
---
 net/9p/client.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/net/9p/client.c b/net/9p/client.c
index cf2d5b60b61b..693e06213a04 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -212,8 +212,6 @@ static int parse_opts(char *opts, struct p9_client *clnt)
 	}
 
 free_and_return:
-	if (ret)
-		v9fs_put_trans(clnt->trans_mod);
 	kfree(tmp_options);
 	return ret;
 }
-- 
2.35.1

Re: [PATCH 1/2] 9p: client_create/destroy: only call trans_mod->close after create

[Dominique Martinet]

Dominique Martinet wrote on Wed, Oct 05, 2022 at 06:51:13AM +0900:
> destroy code would incorrectly call close() if trans_mod exists after some
> hasty code cleanup: we need to make sure we only call close after create
> 
> The new bool added to track this has been added in a hole of the struct
> and will not increase p9_client's size.
> It might be possible to do better with a bit more work, but that will
> have to do for now.
> 
> Link: https://lkml.kernel.org/r/00000000000015ac7905e97ebaed@google.com
> Reported-by: syzbot+67d13108d855f451cafc@syzkaller.appspotmail.com
> Reported-by: Leon Romanovsky <leon@kernel.org>
> Fixes: 3ff51294a055 ("9p: p9_client_create: use p9_client_destroy on failure")

Oh... Fixing tags for stable made me notice this actually wasn't merged
into 5.19 unlike what I thought, so we only have the original bug of
potentially freeing the idr with tags still in it.

That's a much smaller bug and I'll just remove the first
p9_client_destroy on failure patch for this merge window (small leak
that requires root on error) ; then we can take time to properly fix
this one way or another for next cycle.

--
Dominique