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Subject: Re: Misplaced driver_sysfs_remove in really_probe?
To:     Jiri Slaby <jslaby@suse.cz>, Greg KH <gregkh@linuxfoundation.org>,
        rafael@kernel.org,
        Linux kernel mailing list <linux-kernel@vger.kernel.org>
References: <582bf3ba-3733-eb38-cb9c-5b0d329fb068@suse.cz>
From:   Mukesh Ojha <mojha@codeaurora.org>
Message-ID: <c7344584-7dca-648a-8a98-8a47806dd6a5@codeaurora.org>
Date:   Thu, 28 Mar 2019 16:08:44 +0530
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On 3/28/2019 3:36 PM, Jiri Slaby wrote:
> Hi,
>
> since commit 1901fb2604fbcd53201f38725182ea807581159e
> Author: Kay Sievers <kay.sievers@novell.com>
> Date:   Sat Oct 7 21:55:55 2006 +0200
>
>      Driver core: fix "driver" symlink timing
>
> driver_sysfs_remove seems to be misplaced in the fail path of
> really_probe. When driver_sysfs_add fails (or anything which is
> currently above it in dd.c -- be it pinctrl_bind_pins or
> dev->bus->dma_configure), driver_sysfs_remove is called. Given
> dev->driver is set, attempt to remove sysfs device and driver links is
> performed, but it is supposed to fail, as the links do not exist yet.
>
> I am dealing with a Syzkaller WARNING from SLE15-SP1 (4.12) which
> corresponds to the described scenario. Perhaps Syzkaller fault-injected
> a kzalloc failure to pinctrl_bind_pins as I cannot reproduce the report
> at all:
>> WARNING: CPU: 1 PID: 2091 at ../fs/kernfs/dir.c:1481
> kernfs_remove_by_name_ns+0xfa/0x120 fs/kernfs/dir.c:1480
>> Supported: No, Unreleased kernel
>> CPU: 1 PID: 2091 Comm: systemd-udevd Not tainted 4.12.14-396-default
> #1 SLE15-SP1 (unreleased)
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> rel-1.12.0-0-ga698c89-prebuilt.qemu.org 04/01/2014
>> task: ffff880053794fc0 task.stack: ffff880040ea0000
>> RIP: 0010:kernfs_remove_by_name_ns+0xfa/0x120 fs/kernfs/dir.c:1480
>> RSP: 0018:ffff880040ea7488 EFLAGS: 00010282
>> RAX: 000000000000002d RBX: 0000000000000000 RCX: 0000000000000000
>> RDX: 000000000000002d RSI: 1ffff100081d4e48 RDI: ffffed00081d4e85
>> RBP: ffffffffa772a380 R08: 0000000000000000 R09: 0000000000000000
>> R10: ffffffffaa1872c4 R11: 0000000000000000 R12: 0000000000000000
>> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000037
>> FS:  00007f0d24dc0f80(0000) GS:ffff88005e080000(0000)
> knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 000000000045c061 CR3: 000000003b878006 CR4: 0000000000060ee0
>> Call Trace:
>>   driver_sysfs_remove+0xb0/0x110 drivers/base/dd.c:290
>>   really_probe drivers/base/dd.c:433 [inline]
>>   driver_probe_device+0x2b3/0x1200 drivers/base/dd.c:530
>>   __driver_attach+0x1dc/0x280 drivers/base/dd.c:763
>>   bus_for_each_dev+0x146/0x1e0 drivers/base/bus.c:316
>>   bus_add_driver+0x40f/0x850 drivers/base/bus.c:710
>>   driver_register+0x1c9/0x410 drivers/base/driver.c:168
>>   __hid_register_driver+0x1e0/0x2d0 drivers/hid/hid-core.c:2974
>>   ? 0xffffffffc1510000
>>   do_one_initcall+0xb7/0x300 init/main.c:808
>>   do_init_module+0x23e/0x641 kernel/module.c:3515
>>   load_module+0x47d6/0x60b0 kernel/module.c:3867
>>   SYSC_finit_module+0x239/0x2a0 kernel/module.c:3980
>>   do_syscall_64+0x26c/0x6e0 arch/x86/entry/common.c:284
>>   entry_SYSCALL_64_after_hwframe+0x3d/0xa2
> I believe it survived from 2.6.20 to the current tree.
>
> Does it look correct to you? This should help IMO and if you agree I
> will send a proper patch:
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -496,7 +496,7 @@ static int really_probe(struct device *dev, struct
> device_driver *drv)
>          if (driver_sysfs_add(dev)) {
>                  printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
>                          __func__, dev_name(dev));
> -               goto probe_failed;
> +               goto sysfs_failed;
>          }
>
>          if (dev->pm_domain && dev->pm_domain->activate) {
> @@ -546,6 +546,8 @@ static int really_probe(struct device *dev, struct
> device_driver *drv)
>          goto done;
>
>   probe_failed:
> +       driver_sysfs_remove(dev);
> +sysfs_failed:
>          arch_teardown_dma_ops(dev);
>   dma_failed:
>          if (dev->bus)
> @@ -554,7 +556,6 @@ static int really_probe(struct device *dev, struct
> device_driver *drv)
>   pinctrl_bind_failed:
>          device_links_no_driver(dev);
>          devres_release_all(dev);
> -       driver_sysfs_remove(dev);
>          dev->driver = NULL;
>          dev_set_drvdata(dev, NULL);
>          if (dev->pm_domain && dev->pm_domain->dismiss)


Nice observation.
Please send a proper patch.


Cheers,
Mukesh

>
>
>
>
> thanks,