From a57ac7acdcc1665662e369993898194def56e888 Mon Sep 17 00:00:00 2001

From: Johan Hovold <johan@kernel.org>

Date: Wed, 1 Dec 2021 14:25:25 +0100

Subject: [PATCH] firmware: qemu_fw_cfg: fix NULL-pointer deref on duplicate entries

Git-commit: a57ac7acdcc1665662e369993898194def56e888

Alt-commit: d3e305592d69e21e36b76d24ca3c01971a2d09be

Patch-mainline: v5.17-rc1

References: git-fixes

Commit fe3c60684377 ("firmware: Fix a reference count leak.") "fixed"

a kobject leak in the file registration helper by properly calling

kobject_put() for the entry in case registration of the object fails

(e.g. due to a name collision).

This would however result in a NULL pointer dereference when the

release function tries to remove the never added entry from the

fw_cfg_entry_cache list.

Fix this by moving the list-removal out of the release function.

Note that the offending commit was one of the benign looking umn.edu

fixes which was reviewed but not reverted. [1][2]

[1] https://lore.kernel.org/r/202105051005.49BFABCE@keescook

[2] https://lore.kernel.org/all/YIg7ZOZvS3a8LjSv@kroah.com

Fixes: fe3c60684377 ("firmware: Fix a reference count leak.")

Cc: stable@vger.kernel.org      # 5.8

Cc: Qiushi Wu <wu000273@umn.edu>

Cc: Kees Cook <keescook@chromium.org>

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: Johan Hovold <johan@kernel.org>

Link: https://lore.kernel.org/r/20211201132528.30025-2-johan@kernel.org

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Acked-by: Takashi Iwai <tiwai@suse.de>

---

 drivers/firmware/qemu_fw_cfg.c | 5 +----

 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c

index 172c751a4f6c..a9c64ebfc49a 100644

--- a/drivers/firmware/qemu_fw_cfg.c

+++ b/drivers/firmware/qemu_fw_cfg.c

@@ -388,9 +388,7 @@ static void fw_cfg_sysfs_cache_cleanup(void)

 	struct fw_cfg_sysfs_entry *entry, *next;

 	list_for_each_entry_safe(entry, next, &fw_cfg_entry_cache, list) {

-		/* will end up invoking fw_cfg_sysfs_cache_delist()

-		 * via each object's release() method (i.e. destructor)

-		 */

+		fw_cfg_sysfs_cache_delist(entry);

 		kobject_put(&entry->kobj);

 	}

 }

@@ -448,7 +446,6 @@ static void fw_cfg_sysfs_release_entry(struct kobject *kobj)

 {

 	struct fw_cfg_sysfs_entry *entry = to_entry(kobj);

-	fw_cfg_sysfs_cache_delist(entry);

 	kfree(entry);

 }

-- 

2.31.1