Messages in this thread | | | Date | Wed, 2 Nov 2022 10:51:35 +0800 | Subject | Re: [PATCH] comedi: Fix potential memory leak in comedi_init() | From | shangxiaojing <> |
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On 2022/11/2 0:41, Ian Abbott wrote: > On 01/11/2022 11:40, Ian Abbott wrote: >> On 01/11/2022 06:16, shangxiaojing wrote: >>> >>> >>> On 2022/11/1 12:45, Greg KH wrote: >>>> On Tue, Nov 01, 2022 at 11:21:25AM +0800, Shang XiaoJing wrote: >>>>> comedi_init() will goto out_unregister_chrdev_region if cdev_add() >>>>> failed, which won't free the resource alloced in kobject_set_name(). >>>>> Call kfree_const() to free the leaked name before goto >>>>> out_unregister_chrdev_region. >>>>> >>>>> unreferenced object 0xffff8881000fa8c0 (size 8): >>>>> comm "modprobe", pid 239, jiffies 4294905173 (age 51.308s) >>>>> hex dump (first 8 bytes): >>>>> 63 6f 6d 65 64 69 00 ff comedi.. >>>>> backtrace: >>>>> [<000000005f9878f7>] __kmalloc_node_track_caller+0x4c/0x1c0 >>>>> [<000000000fd70302>] kstrdup+0x3f/0x70 >>>>> [<000000009428bc33>] kstrdup_const+0x46/0x60 >>>>> [<00000000ed50d9de>] kvasprintf_const+0xdb/0xf0 >>>>> [<00000000b2766964>] kobject_set_name_vargs+0x3c/0xe0 >>>>> [<00000000f2424ef7>] kobject_set_name+0x62/0x90 >>>>> [<000000005d5a125b>] 0xffffffffa0013098 >>>>> [<00000000f331e663>] do_one_initcall+0x7a/0x380 >>>>> [<00000000aa7bac96>] do_init_module+0x5c/0x230 >>>>> [<000000005fd72335>] load_module+0x227d/0x2420 >>>>> [<00000000ad550cf1>] __do_sys_finit_module+0xd5/0x140 >>>>> [<00000000069a60c5>] do_syscall_64+0x3f/0x90 >>>>> [<00000000c5e0d521>] entry_SYSCALL_64_after_hwframe+0x63/0xcd >>>>> >>>>> Fixes: ed9eccbe8970 ("Staging: add comedi core") >>>>> Signed-off-by: Shang XiaoJing <shangxiaojing@huawei.com> >>>>> --- >>>>> drivers/comedi/comedi_fops.c | 5 ++++- >>>>> 1 file changed, 4 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/drivers/comedi/comedi_fops.c >>>>> b/drivers/comedi/comedi_fops.c >>>>> index e2114bcf815a..2c508c2cf6f6 100644 >>>>> --- a/drivers/comedi/comedi_fops.c >>>>> +++ b/drivers/comedi/comedi_fops.c >>>>> @@ -3379,8 +3379,11 @@ static int __init comedi_init(void) >>>>> retval = cdev_add(&comedi_cdev, MKDEV(COMEDI_MAJOR, 0), >>>>> COMEDI_NUM_MINORS); >>>>> - if (retval) >>>>> + if (retval) { >>>>> + kfree_const(comedi_cdev.kobj.name); >>>>> + comedi_cdev.kobj.name = NULL; >>>>> goto out_unregister_chrdev_region; >>>>> + } >>>> >>>> A driver should never have to poke around in the internals of a cdev >>>> object like this. Please fix the cdev core to not need this if >>>> cdev_add() fails. >> >> Or at least there should be a function that can be called to undo the >> allocations of kobject_set_name(). > > Looking at it a bit more, cdev_init() calls kobject_init(), and > kobject_init() requires a matching call to kobject_put(). Nothing is > calling kobject_put() in this situation. Calling cdev_del() will call > kobject_put(), so is that the correct way to clean up after cdev_init() > if the call to cdev_add() fails? >
Some cdev call cdev_del() when cdev_add() failed (like init_dvbdev()), and at that time the cdev_unmap() in cdev_del() won't do anything due to the failure of cdev_add(), which is calling the kobject_put() when cdev_add() failed. But I'm not sure which one is better.
Thanks, -- Shang XiaoJing
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