Messages in this thread Patch in this message | | | Date | Tue, 10 Jan 2012 13:55:06 -0800 | From | Greg KH <> | Subject | [03/49] firmware: Fix an oops on reading fw_priv->fw in sysfs loading file |
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3.2-stable review patch. If anyone has any objections, please let me know.
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From: Neil Horman <nhorman@tuxdriver.com>
commit eea915bb0d1358755f151eaefb8208a2d5f3e10c upstream.
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 <nhorman@tuxdriver.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- drivers/base/firmware_class.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-)
--- a/drivers/base/firmware_class.c +++ b/drivers/base/firmware_class.c @@ -226,13 +226,13 @@ static ssize_t firmware_loading_store(st 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(st 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(st fw_load_abort(fw_priv); break; } - +out: + mutex_unlock(&fw_lock); return count; }
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