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authorNeil Horman <nhorman@tuxdriver.com>2012-01-02 15:31:23 -0500
committerGreg Kroah-Hartman <gregkh@suse.de>2012-01-12 11:29:17 -0800
commita5a0cdd640258b80e116de11517dd6482ab6f229 (patch)
treef7a304d689c63ac3b00f3b9bc0c1e5506ac9a5e4 /drivers
parent170797705f7ccb335e9fe3f61967a4d465846642 (diff)
downloadvexpress-lsk-a5a0cdd640258b80e116de11517dd6482ab6f229.tar.gz
firmware: Fix an oops on reading fw_priv->fw in sysfs loading file
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>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/base/firmware_class.c14
1 files changed, 7 insertions, 7 deletions
diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
index 06ed6b4e7df..3719c94be19 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;
}