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    SubjectRe: INFO: REPRODUCED: memory leak in gpio device in 6.2-rc6
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    On 15.2.2023. 11:53, Andy Shevchenko wrote:
    > 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!

    No sweat. It was worth the effort.

    > 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).

    I must admit that is looks like hieroglyphs to me. My learning curve had not
    yet reached that point of debugging memory leaks in the kernel drivers ...

    >> root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/gpio# echo clear > /sys/kernel/debug/kmemleak
    >> root@marvin-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@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/gpio# echo scan > /sys/kernel/debug/kmemleak
    >> root@marvin-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@marvin-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@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/gpio#
    >>
    >> I can verify that I build the right patch:
    >>
    >> marvin@marvin-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@marvin-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?
    >

    --
    Mirsad Todorovac
    System engineer
    Faculty of Graphic Arts | Academy of Fine Arts
    University of Zagreb
    Republic of Croatia, the European Union

    Sistem inženjer
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