# CVE-2021-47387: linux: In the Linux kernel, the following vulnerability has been resolved:  cpufreq: schedutil: Use kobject release() method...

CVE-2021-47387 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47387, released May 21, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2021-47387
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0025
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 21, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  cpufreq: schedutil: Use kobject release() method to free sugov_tunables  The struct sugov_tunables is protected by the kobject, so we can't free it directly. Otherwise we would get a call trace like this:   ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x30   WARNING: CPU: 3 PID: 720 at lib/debugobjects.c:505 debug_print_object+0xb8/0x100   Modules linked in:   CPU: 3 PID: 720 Comm: a.sh Tainted: G        W         5.14.0-rc1-next-20210715-yocto-standard+ #507   Hardware name: Marvell OcteonTX CN96XX board (DT)   pstate: 40400009 (nZcv daif +PAN -UAO -TCO BTYPE=--)   pc : debug_print_object+0xb8/0x100   lr : debug_print_object+0xb8/0x100   sp : ffff80001ecaf910   x29: ffff80001ecaf910 x28: ffff00011b10b8d0 x27: ffff800011043d80   x26: ffff00011a8f0000 x25: ffff800013cb3ff0 x24: 0000000000000000   x23: ffff80001142aa68 x22: ffff800011043d80 x21: ffff00010de46f20   x20: ffff800013c0c520 x19: ffff800011d8f5b0 x18: 0000000000000010   x17: 6e6968207473696c x16: 5f72656d6974203a x15: 6570797420746365   x14: 6a626f2029302065 x13: 303378302f307830 x12: 2b6e665f72656d69   x11: ffff8000124b1560 x10: ffff800012331520 x9 : ffff8000100ca6b0   x8 : 000000000017ffe8 x7 : c0000000fffeffff x6 : 0000000000000001   x5 : ffff800011d8c000 x4 : ffff800011d8c740 x3 : 0000000000000000   x2 : ffff0001108301c0 x1 : ab3c90eedf9c0f00 x0 : 0000000000000000   Call trace:    debug_print_object+0xb8/0x100    __debug_check_no_obj_freed+0x1c0/0x230    debug_check_no_obj_freed+0x20/0x88    slab_free_freelist_hook+0x154/0x1c8    kfree+0x114/0x5d0    sugov_exit+0xbc/0xc0    cpufreq_exit_governor+0x44/0x90    cpufreq_set_policy+0x268/0x4a8    store_scaling_governor+0xe0/0x128    store+0xc0/0xf0    sysfs_kf_write+0x54/0x80    kernfs_fop_write_iter+0x128/0x1c0    new_sync_write+0xf0/0x190    vfs_write+0x2d4/0x478    ksys_write+0x74/0x100    __arm64_sys_write+0x24/0x30    invoke_syscall.constprop.0+0x54/0xe0    do_el0_svc+0x64/0x158    el0_svc+0x2c/0xb0    el0t_64_sync_handler+0xb0/0xb8    el0t_64_sync+0x198/0x19c   irq event stamp: 5518   hardirqs last  enabled at (5517): [<ffff8000100cbd7c>] console_unlock+0x554/0x6c8   hardirqs last disabled at (5518): [<ffff800010fc0638>] el1_dbg+0x28/0xa0   softirqs last  enabled at (5504): [<ffff8000100106e0>] __do_softirq+0x4d0/0x6c0   softirqs last disabled at (5483): [<ffff800010049548>] irq_exit+0x1b0/0x1b8  So split the original sugov_tunables_free() into two functions, sugov_clear_global_tunables() is just used to clear the global_tunables and the new sugov_tunables_free() is used as kobj_type::release to release the sugov_tunables safely.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.14.12-1 | [DEBIAN-CVE-2021-47387](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47387.md) | May 21, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.14.12-1 | [DEBIAN-CVE-2021-47387](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47387.md) | May 21, 2024 |
| Linux | linux Debian 14 | 5.14.12-1 | [DEBIAN-CVE-2021-47387](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47387.md) | May 21, 2024 |

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