lkml.org 
[lkml]   [2016]   [Aug]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Date
    Subject[PATCH 3.16 195/305] base: make module_create_drivers_dir race-free
    3.16.37-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Jiri Slaby <jslaby@suse.cz>

    commit 7e1b1fc4dabd6ec8e28baa0708866e13fa93c9b3 upstream.

    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)
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    drivers/base/module.c | 8 +++++---
    1 file changed, 5 insertions(+), 3 deletions(-)

    --- a/drivers/base/module.c
    +++ b/drivers/base/module.c
    @@ -24,10 +24,12 @@ static char *make_driver_name(struct dev

    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)
    \
     
     \ /
      Last update: 2016-09-17 09:56    [W:2.552 / U:0.936 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site