From eea915bb0d1358755f151eaefb8208a2d5f3e10c Mon Sep 17 00:00:00 2001 From: Neil Horman Date: Mon, 2 Jan 2012 15:31:23 -0500 Subject: [PATCH] firmware: Fix an oops on reading fw_priv->fw in sysfs loading file This oops was reported recently: firmware_loading_store+0xf9/0x17b dev_attr_store+0x20/0x22 sysfs_write_file+0x101/0x134 vfs_write+0xac/0xf3 sys_write+0x4a/0x6e system_call_fastpath+0x16/0x1b The complete backtrace was unfortunately not captured, but details can be found here: https://bugzilla.redhat.com/show_bug.cgi?id=769920 The cause is fairly clear. Its caused by the fact that firmware_loading_store has a case 0 in its switch statement that reads and writes the fw_priv->fw poniter without the protection of the fw_lock mutex. since there is a window between the time that _request_firmware sets fw_priv->fw to NULL and the time the corresponding sysfs file is unregistered, its possible for a user space application to race in, and write a zero to the loading file, causing a NULL dereference in firmware_loading_store. Fix it by extending the protection of the fw_lock mutex to cover all of the firware_loading_store function. Signed-off-by: Neil Horman Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/base/firmware_class.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c index 06ed6b4e7df5..3719c94be19c 100644 --- a/drivers/base/firmware_class.c +++ b/drivers/base/firmware_class.c @@ -226,13 +226,13 @@ static ssize_t firmware_loading_store(struct device *dev, int loading = simple_strtol(buf, NULL, 10); int i; + mutex_lock(&fw_lock); + + if (!fw_priv->fw) + goto out; + switch (loading) { case 1: - mutex_lock(&fw_lock); - if (!fw_priv->fw) { - mutex_unlock(&fw_lock); - break; - } firmware_free_data(fw_priv->fw); memset(fw_priv->fw, 0, sizeof(struct firmware)); /* If the pages are not owned by 'struct firmware' */ @@ -243,7 +243,6 @@ static ssize_t firmware_loading_store(struct device *dev, fw_priv->page_array_size = 0; fw_priv->nr_pages = 0; set_bit(FW_STATUS_LOADING, &fw_priv->status); - mutex_unlock(&fw_lock); break; case 0: if (test_bit(FW_STATUS_LOADING, &fw_priv->status)) { @@ -274,7 +273,8 @@ static ssize_t firmware_loading_store(struct device *dev, fw_load_abort(fw_priv); break; } - +out: + mutex_unlock(&fw_lock); return count; } -- 2.20.1