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Date: Mon, 24 Jan 2022 19:40:57 +0100 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Qiushi Wu <wu000273@....edu>, Kees Cook <keescook@...omium.org>, Johan Hovold <johan@...nel.org>, "Michael S. Tsirkin" <mst@...hat.com> Subject: [PATCH 4.19 019/239] firmware: qemu_fw_cfg: fix NULL-pointer deref on duplicate entries From: Johan Hovold <johan@...nel.org> commit d3e305592d69e21e36b76d24ca3c01971a2d09be upstream. 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@...r.kernel.org # 5.8 Cc: Qiushi Wu <wu000273@....edu> Cc: Kees Cook <keescook@...omium.org> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org> Signed-off-by: Johan Hovold <johan@...nel.org> Link: https://lore.kernel.org/r/20211201132528.30025-2-johan@kernel.org Signed-off-by: Michael S. Tsirkin <mst@...hat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- drivers/firmware/qemu_fw_cfg.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) --- a/drivers/firmware/qemu_fw_cfg.c +++ b/drivers/firmware/qemu_fw_cfg.c @@ -385,9 +385,7 @@ static void fw_cfg_sysfs_cache_cleanup(v 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); } } @@ -445,7 +443,6 @@ static void fw_cfg_sysfs_release_entry(s { struct fw_cfg_sysfs_entry *entry = to_entry(kobj); - fw_cfg_sysfs_cache_delist(entry); kfree(entry); }
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