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authorJiri Slaby <jslaby@suse.cz>2016-06-10 11:54:32 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-06-16 05:21:31 +0300
commit7e1b1fc4dabd6ec8e28baa0708866e13fa93c9b3 (patch)
tree0d2b5accaf22a5e3a6fce671df7f8aa2b8b3c2fd
parent75f0b68b75dabb3ff551440163fd67b3fc62901a (diff)
downloadlinux-7e1b1fc4dabd6ec8e28baa0708866e13fa93c9b3.tar.xz
base: make module_create_drivers_dir race-free
Modules which register drivers via standard path (driver_register) in parallel can cause a warning: WARNING: CPU: 2 PID: 3492 at ../fs/sysfs/dir.c:31 sysfs_warn_dup+0x62/0x80 sysfs: cannot create duplicate filename '/module/saa7146/drivers' Modules linked in: hexium_gemini(+) mxb(+) ... ... Call Trace: ... [<ffffffff812e63a2>] sysfs_warn_dup+0x62/0x80 [<ffffffff812e6487>] sysfs_create_dir_ns+0x77/0x90 [<ffffffff8140f2c4>] kobject_add_internal+0xb4/0x340 [<ffffffff8140f5b8>] kobject_add+0x68/0xb0 [<ffffffff8140f631>] kobject_create_and_add+0x31/0x70 [<ffffffff8157a703>] module_add_driver+0xc3/0xd0 [<ffffffff8155e5d4>] bus_add_driver+0x154/0x280 [<ffffffff815604c0>] driver_register+0x60/0xe0 [<ffffffff8145bed0>] __pci_register_driver+0x60/0x70 [<ffffffffa0273e14>] saa7146_register_extension+0x64/0x90 [saa7146] [<ffffffffa0033011>] hexium_init_module+0x11/0x1000 [hexium_gemini] ... As can be (mostly) seen, driver_register causes this call sequence: -> bus_add_driver -> module_add_driver -> module_create_drivers_dir The last one creates "drivers" directory in /sys/module/<...>. When this is done in parallel, the directory is attempted to be created twice at the same time. This can be easily reproduced by loading mxb and hexium_gemini in parallel: while :; do modprobe mxb & modprobe hexium_gemini wait rmmod mxb hexium_gemini saa7146_vv saa7146 done saa7146 calls pci_register_driver for both mxb and hexium_gemini, which means /sys/module/saa7146/drivers is to be created for both of them. Fix this by a new mutex in module_create_drivers_dir which makes the test-and-create "drivers" dir atomic. I inverted the condition and removed 'return' to avoid multiple unlocks or a goto. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Fixes: fe480a2675ed (Modules: only add drivers/ direcory if needed) Cc: v2.6.21+ <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/base/module.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/drivers/base/module.c b/drivers/base/module.c
index db930d3ee312..2a215780eda2 100644
--- a/drivers/base/module.c
+++ b/drivers/base/module.c
@@ -24,10 +24,12 @@ static char *make_driver_name(struct device_driver *drv)
static void module_create_drivers_dir(struct module_kobject *mk)
{
- if (!mk || mk->drivers_dir)
- return;
+ static DEFINE_MUTEX(drivers_dir_mutex);
- mk->drivers_dir = kobject_create_and_add("drivers", &mk->kobj);
+ mutex_lock(&drivers_dir_mutex);
+ if (mk && !mk->drivers_dir)
+ mk->drivers_dir = kobject_create_and_add("drivers", &mk->kobj);
+ mutex_unlock(&drivers_dir_mutex);
}
void module_add_driver(struct module *mod, struct device_driver *drv)