Date:   Wed, 15 Feb 2023 12:53:17 +0200
From:   Andy Shevchenko <andriy.shevchenko@...el.com>
To:     Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
Cc:     linux-gpio@...r.kernel.org,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        linux-kernel@...r.kernel.org,
        Thorsten Leemhuis <regressions@...mhuis.info>
Subject: Re: INFO: REPRODUCED: memory leak in gpio device in 6.2-rc6

On Tue, Feb 14, 2023 at 07:19:16PM +0100, Mirsad Goran Todorovac wrote:
> On 12. 02. 2023. 15:19, Andy Shevchenko wrote:
> > On Wed, Feb 08, 2023 at 08:55:24PM +0100, Mirsad Goran Todorovac wrote:
> >> On 31. 01. 2023. 10:36, Mirsad Goran Todorovac wrote:
> >>> I came across this memory leak apparently in the GPIO device driver.
> >>> It is still present in 6.2-rc6 release candidate kernel (just ran kselftest).
> >>>
> >>> This is a vanilla Torvalds tree kernel with MGLRU and KMEMLEAK (obviously)
> >>> enabled.
> >>>
> >>> If you think this bug is significant, I can attempt the bug bisect in the
> >>> environment that triggered it (Lenovo LENOVO_MT_10TX_BU_Lenovo_FM_V530S-07ICB)
> >>> with BIOS M22KT49A from 11/10/2022 and AlmaLinux 8.7.
> >>>
> >>> Here is the /sys/kernel/debug/kmemleak output:
> >>>
> >>> unreferenced object 0xffff9e67ad71f160 (size 32):
> >>>   comm "gpio-sim.sh", pid 208926, jiffies 4372229685 (age 2101.564s)
> >>>   hex dump (first 32 bytes):
> >>>     67 70 69 6f 2d 73 69 6d 2e 30 2d 6e 6f 64 65 30  gpio-sim.0-node0
> >>>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> >>>   backtrace:
> >>>     [<0000000098bf3d1b>] slab_post_alloc_hook+0x91/0x320
> >>>     [<00000000da3205c5>] __kmem_cache_alloc_node+0x1bf/0x2b0
> >>>     [<00000000aa51a58a>] __kmalloc_node_track_caller+0x55/0x140
> >>>     [<00000000bd682ecc>] kvasprintf+0x6b/0xd0
> >>>     [<00000000a3431d55>] kasprintf+0x4e/0x70
> >>>     [<00000000f52d2629>] gpio_sim_device_config_live_store+0x401/0x59d [gpio_sim]
> >>>     [<00000000673fc6df>] configfs_write_iter+0xcc/0x130
> >>>     [<000000001d5d0829>] vfs_write+0x2b4/0x3d0
> >>>     [<00000000d2336251>] ksys_write+0x61/0xe0
> >>>     [<00000000f7015bb1>] __x64_sys_write+0x1a/0x20
> >>>     [<000000008ac743d2>] do_syscall_64+0x58/0x80
> >>>     [<000000004d7b7d50>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

> Sorry, but unfortunately this patch didn't fix the memleak. Please see the result:

Thank you for give a try!

Yeah, that's why I put that I'm skeptical, because while patch is correct per
se it wouldn't prevent the initial leakage (it seems it happens due to other
circumstances).

> root@...vin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/gpio# echo clear > /sys/kernel/debug/kmemleak
> root@...vin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/gpio# time ./gpio-sim.sh
> trap: SIGTERM: bad trap
> 1. chip_name and dev_name attributes
> 1.1. Chip name is communicated to user
> 1.2. chip_name returns 'none' if the chip is still pending
> 1.3. Device name is communicated to user
> 2. Creating and configuring simulated chips
> 2.1. Default number of lines is 1
> 2.2. Number of lines can be specified
> 2.3. Label can be set
> 2.4. Label can be left empty
> 2.5. Line names can be configured
> 2.6. Line config can remain unused if offset is greater than number of lines
> 2.7. Line configfs directory names are sanitized
> 2.8. Multiple chips can be created
> 2.9. Can't modify settings when chip is live
> 2.10. Can't create line items when chip is live
> 2.11. Probe errors are propagated to user-space
> 2.12. Cannot enable a chip without any GPIO banks
> 2.13. Duplicate chip labels are not allowed
> 2.14. Lines can be hogged
> 3. Controlling simulated chips
> 3.1. Pull can be set over sysfs
> 3.2. Pull can be read from sysfs
> 3.3. Incorrect input in sysfs is rejected
> 3.4. Can't write to value
> 4. Simulated GPIO chips are functional
> 4.1. Values can be read from sysfs
> 4.2. Bias settings work correctly
> GPIO gpio-sim test PASS
> 
> real	0m1.120s
> user	0m0.283s
> sys	0m0.842s
> root@...vin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/gpio# echo scan > /sys/kernel/debug/kmemleak
> root@...vin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/gpio# cat /sys/kernel/debug/kmemleak 
> unreferenced object 0xffff91f019219660 (size 32):
>   comm "gpio-sim.sh", pid 11223, jiffies 4295028142 (age 87.304s)
>   hex dump (first 32 bytes):
>     67 70 69 6f 2d 73 69 6d 2e 30 2d 6e 6f 64 65 30  gpio-sim.0-node0
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<ffffffff86fcd408>] __kmem_cache_alloc_node+0x1d8/0x330
>     [<ffffffff86f4c271>] __kmalloc_node_track_caller+0x51/0xd0
>     [<ffffffff872fb359>] kvasprintf+0x69/0xd0
>     [<ffffffff872fb4ce>] kasprintf+0x4e/0x70
>     [<ffffffffc1864553>] gpio_sim_device_config_live_store+0x483/0x6b5 [gpio_sim]
>     [<ffffffff870dde9c>] configfs_write_iter+0xcc/0x130
>     [<ffffffff87016869>] vfs_write+0x1f9/0x3b0
>     [<ffffffff87016dab>] ksys_write+0x6b/0xf0
>     [<ffffffff87016e59>] __x64_sys_write+0x19/0x20
>     [<ffffffff87b91188>] do_syscall_64+0x58/0x80
>     [<ffffffff87c000aa>] entry_SYSCALL_64_after_hwframe+0x72/0xdc
> root@...vin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/gpio# uname -rms
> Linux 6.2.0-rc8-lru-km-andy-00015-gf6feea56f66d-dirty x86_64
> root@...vin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/gpio# 
> 
> I can verify that I build the right patch:
> 
> marvin@...vin-IdeaPad-3-15ITL6:~/linux/kernel/linux_torvalds$ git diff
> diff --git a/drivers/gpio/gpio-sim.c b/drivers/gpio/gpio-sim.c
> index 60514bc5454f..7f79e49b23d7 100644
> --- a/drivers/gpio/gpio-sim.c
> +++ b/drivers/gpio/gpio-sim.c
> @@ -954,9 +954,9 @@ static void gpio_sim_device_deactivate_unlocked(struct gpio_sim_device *dev)
>  
>         swnode = dev_fwnode(&dev->pdev->dev);
>         platform_device_unregister(dev->pdev);
> +       gpio_sim_remove_hogs(dev);
>         gpio_sim_remove_swnode_recursive(swnode);
>         dev->pdev = NULL;
> -       gpio_sim_remove_hogs(dev);
>  }
>  
>  static ssize_t
> marvin@...vin-IdeaPad-3-15ITL6:~/linux/kernel/linux_torvalds$ 
> 
> Alternatively, I could try to bisect if you think it's prudent to try that.
> But first I need a stroll after this kernel build :-)
> 
> Do you think that knowing when the bug was introduced might help find the culprit?

-- 
With Best Regards,
Andy Shevchenko

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