CVE-2022-48838

MEDIUM
Published Jul 16, 2024 Modified Nov 21, 2024 CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: Fix use-after-free bug by not setting udc->dev.driver The syzbot fuzzer found a use-after-free bug: BUG: KASAN: use-after-free in dev_uevent+0x712/0x780 drivers/base/core.c:2320 Read of size 8 at addr ffff88802b934098 by task udevd/3689 CPU: 2 PID: 3689 Comm: udevd Not tainted 5.17.0-rc4-syzkaller-00229-g4f12b742eb2b #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description.constprop.0.cold+0x8d/0x303 mm/kasan/report.c:255 __kasan_report mm/kasan/report.c:442 [inline] kasan_report.cold+0x83/0xdf mm/kasan/report.c:459 dev_uevent+0x712/0x780 drivers/base/core.c:2320 uevent_show+0x1b8/0x380 drivers/base/core.c:2391 dev_attr_show+0x4b/0x90 drivers/base/core.c:2094 Although the bug manifested in the driver core, the real cause was a race with the gadget core. dev_uevent() does: if (dev->driver) add_uevent_var(env, "DRIVER=%s", dev->driver->name); and between the test and the dereference of dev->driver, the gadget core sets dev->driver to NULL. The race wouldn't occur if the gadget core registered its devices on a real bus, using the standard synchronization techniques of the driver core. However, it's not necessary to make such a large change in order to fix this bug; all we need to do is make sure that udc->dev.driver is always NULL. In fact, there is no reason for udc->dev.driver ever to be set to anything, let alone to the value it currently gets: the address of the gadget's driver. After all, a gadget driver only knows how to manage a gadget, not how to manage a UDC. This patch simply removes the statements in the gadget core that touch udc->dev.driver.

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CVSS v3.1 Score

5.5
MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness Type (CWE)

CWE-416 Use After Free

Affected Products

Vendor Product
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel

References

Advisories & Patches

https://git.kernel.org/stable/c/00bdd9bf1ac6d401ad926d3d8df41b9f1399f646 https://git.kernel.org/stable/c/16b1941eac2bd499f065a6739a40ce0011a3d740 https://git.kernel.org/stable/c/2015c23610cd0efadaeca4d3a8d1dae9a45aa35a https://git.kernel.org/stable/c/2282a6eb6d4e118e294e43dcc421e0e0fe4040b5 https://git.kernel.org/stable/c/27d64436984fb8835a8b7e95993193cc478b162e https://git.kernel.org/stable/c/4325124dde6726267813c736fee61226f1d38f0b https://git.kernel.org/stable/c/609a7119bffe3ddd7c93f2fa65be8917e02a0b7e https://git.kernel.org/stable/c/e2d3a7009e505e120805f449c832942660f3f7f3 https://git.kernel.org/stable/c/00bdd9bf1ac6d401ad926d3d8df41b9f1399f646 https://git.kernel.org/stable/c/16b1941eac2bd499f065a6739a40ce0011a3d740 https://git.kernel.org/stable/c/2015c23610cd0efadaeca4d3a8d1dae9a45aa35a https://git.kernel.org/stable/c/2282a6eb6d4e118e294e43dcc421e0e0fe4040b5 https://git.kernel.org/stable/c/27d64436984fb8835a8b7e95993193cc478b162e https://git.kernel.org/stable/c/4325124dde6726267813c736fee61226f1d38f0b https://git.kernel.org/stable/c/609a7119bffe3ddd7c93f2fa65be8917e02a0b7e https://git.kernel.org/stable/c/e2d3a7009e505e120805f449c832942660f3f7f3

Frequently Asked Questions

What is CVE-2022-48838? +
In the Linux kernel, the following vulnerability has been resolved: usb: gadget: Fix use-after-free bug by not setting udc->dev.driver The syzbot fuzzer found a use-after-free bug: BUG: KASAN: use-after-free in dev_uevent+0x712/0x780 drivers/base/core.c:2320 Read of size 8 at addr ffff88802b934098 by task udevd/3689 CPU: 2 PID: 3689 Comm: udevd Not tainted 5.17.0-rc4-syzkaller-00229-g4f12b742eb2b #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description.constprop.0.cold+0x8d/0x303 mm/kasan/report.c:255 __kasan_report mm/kasan/report.c:442 [inline] kasan_report.cold+0x83/0xdf mm/kasan/report.c:459 dev_uevent+0x712/0x780 drivers/base/core.c:2320 uevent_show+0x1b8/0x380 drivers/base/core.c:2391 dev_attr_show+0x4b/0x90 drivers/base/core.c:2094 Although the bug manifested in the driver core, the real cause was a race with the gadget core. dev_uevent() does: if (dev->driver) add_uevent_var(env, "DRIVER=%s", dev->driver->name); and between the test and the dereference of dev->driver, the gadget core sets dev->driver to NULL. The race wouldn't occur if the gadget core registered its devices on a real bus, using the standard synchronization techniques of the driver core. However, it's not necessary to make such a large change in order to fix this bug; all we need to do is make sure that udc->dev.driver is always NULL. In fact, there is no reason for udc->dev.driver ever to be set to anything, let alone to the value it currently gets: the address of the gadget's driver. After all, a gadget driver only knows how to manage a gadget, not how to manage a UDC. This patch simply removes the statements in the gadget core that touch udc->dev.driver. It has a CVSS v3.1 base score of 5.5 (MEDIUM).
How severe is CVE-2022-48838? +
CVE-2022-48838 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.
What products are affected by CVE-2022-48838? +
CVE-2022-48838 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.
How do I check if I'm vulnerable to CVE-2022-48838? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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