patch "stm class: Fix a module refcount leak in policy creation error path" added to char-misc-next

patch "stm class: Fix a module refcount leak in policy creation error path" added to char-misc-next

[gregkh]

This is a note to let you know that I've just added the patch titled

    stm class: Fix a module refcount leak in policy creation error path

to my char-misc git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-next branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release
during the merge window.

If you have any questions about this process, please let me know.


>From c18614a1a11276837bdd44403d84d207c9951538 Mon Sep 17 00:00:00 2001
From: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Date: Wed, 19 Dec 2018 17:19:20 +0200
Subject: stm class: Fix a module refcount leak in policy creation error path

Commit c7fd62bc69d0 ("stm class: Introduce framing protocol drivers")
adds a bug into the error path of policy creation, that would do a
module_put() on a wrong module, if one tried to create a policy for
an stm device which already has a policy, using a different protocol.
IOW,

| mkdir /config/stp-policy/dummy_stm.0:p_basic.test
| mkdir /config/stp-policy/dummy_stm.0:p_sys-t.test # puts "p_basic"
| mkdir /config/stp-policy/dummy_stm.0:p_sys-t.test # "p_basic" -> -1

throws:

| general protection fault: 0000 [#1] SMP PTI
| CPU: 3 PID: 2887 Comm: mkdir
| RIP: 0010:module_put.part.31+0xe/0x90
| Call Trace:
|  module_put+0x13/0x20
|  stm_put_protocol+0x11/0x20 [stm_core]
|  stp_policy_make+0xf1/0x210 [stm_core]
|  ? __kmalloc+0x183/0x220
|  ? configfs_mkdir+0x10d/0x4c0
|  configfs_mkdir+0x169/0x4c0
|  vfs_mkdir+0x108/0x1c0
|  do_mkdirat+0xe8/0x110
|  __x64_sys_mkdir+0x1b/0x20
|  do_syscall_64+0x5a/0x140
|  entry_SYSCALL_64_after_hwframe+0x44/0xa9

Correct this sad mistake by calling calling 'put' on the correct
reference, which happens to match another error path in the same
function, so we consolidate the two at the same time.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Fixes: c7fd62bc69d0 ("stm class: Introduce framing protocol drivers")
Reported-by: Ammy Yi <ammy.yi@intel.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/hwtracing/stm/policy.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/hwtracing/stm/policy.c b/drivers/hwtracing/stm/policy.c
index 0910ec807187..4b9e44b227d8 100644
--- a/drivers/hwtracing/stm/policy.c
+++ b/drivers/hwtracing/stm/policy.c
@@ -440,10 +440,8 @@ stp_policy_make(struct config_group *group, const char *name)
 
 	stm->policy = kzalloc(sizeof(*stm->policy), GFP_KERNEL);
 	if (!stm->policy) {
-		mutex_unlock(&stm->policy_mutex);
-		stm_put_protocol(pdrv);
-		stm_put_device(stm);
-		return ERR_PTR(-ENOMEM);
+		ret = ERR_PTR(-ENOMEM);
+		goto unlock_policy;
 	}
 
 	config_group_init_type_name(&stm->policy->group, name,
@@ -458,7 +456,11 @@ stp_policy_make(struct config_group *group, const char *name)
 	mutex_unlock(&stm->policy_mutex);
 
 	if (IS_ERR(ret)) {
-		stm_put_protocol(stm->pdrv);
+		/*
+		 * pdrv and stm->pdrv at this point can be quite different,
+		 * and only one of them needs to be 'put'
+		 */
+		stm_put_protocol(pdrv);
 		stm_put_device(stm);
 	}
 
-- 
2.20.1