CVE-2021-4439: isdn: cpai: check ctr->cnr to avoid array index out of bound
First published: Thu Jun 20 2024(Updated: )
In the Linux kernel, the following vulnerability has been resolved: isdn: cpai: check ctr->cnr to avoid array index out of bound The cmtp_add_connection() would add a cmtp session to a controller and run a kernel thread to process cmtp. __module_get(THIS_MODULE); session->task = kthread_run(cmtp_session, session, "kcmtpd_ctr_%d", session->num); During this process, the kernel thread would call detach_capi_ctr() to detach a register controller. if the controller was not attached yet, detach_capi_ctr() would trigger an array-index-out-bounds bug. [ 46.866069][ T6479] UBSAN: array-index-out-of-bounds in drivers/isdn/capi/kcapi.c:483:21 [ 46.867196][ T6479] index -1 is out of range for type 'capi_ctr *[32]' [ 46.867982][ T6479] CPU: 1 PID: 6479 Comm: kcmtpd_ctr_0 Not tainted 5.15.0-rc2+ #8 [ 46.869002][ T6479] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014 [ 46.870107][ T6479] Call Trace: [ 46.870473][ T6479] dump_stack_lvl+0x57/0x7d [ 46.870974][ T6479] ubsan_epilogue+0x5/0x40 [ 46.871458][ T6479] __ubsan_handle_out_of_bounds.cold+0x43/0x48 [ 46.872135][ T6479] detach_capi_ctr+0x64/0xc0 [ 46.872639][ T6479] cmtp_session+0x5c8/0x5d0 [ 46.873131][ T6479] ? __init_waitqueue_head+0x60/0x60 [ 46.873712][ T6479] ? cmtp_add_msgpart+0x120/0x120 [ 46.874256][ T6479] kthread+0x147/0x170 [ 46.874709][ T6479] ? set_kthread_struct+0x40/0x40 [ 46.875248][ T6479] ret_from_fork+0x1f/0x30 [ 46.875773][ T6479]
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Linux Kernel | <4.4.290 | |
| Linux Kernel | >=4.5<4.9.288 | |
| Linux Kernel | >=4.10<4.14.253 | |
| Linux Kernel | >=4.15<4.19.214 | |
| Linux Kernel | >=4.20<5.4.156 | |
| Linux Kernel | >=5.5<5.10.76 | |
| Linux Kernel | >=5.11<5.14.15 | |
| Linux Kernel | =5.15-rc1 | |
| Linux Kernel | =5.15-rc2 | |
| Linux Kernel | =5.15-rc3 | |
| Linux Kernel | =5.15-rc4 | |
| Linux Kernel | =5.15-rc5 |
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Reference Links
- https://git.kernel.org/stable/c/e8b8de17e164c9f1b7777f1c6f99d05539000036
- https://git.kernel.org/stable/c/24219a977bfe3d658687e45615c70998acdbac5a
- https://git.kernel.org/stable/c/9b6b2db77bc3121fe435f1d4b56e34de443bec75
- https://git.kernel.org/stable/c/7d91adc0ccb060ce564103315189466eb822cc6a
- https://git.kernel.org/stable/c/285e9210b1fab96a11c0be3ed5cea9dd48b6ac54
- https://git.kernel.org/stable/c/7f221ccbee4ec662e2292d490a43ce6c314c4594
- https://git.kernel.org/stable/c/cc20226e218a2375d50dd9ac14fb4121b43375ff
- https://git.kernel.org/stable/c/1f3e2e97c003f80c4b087092b225c8787ff91e4d
Frequently Asked Questions
What is the severity of CVE-2021-4439?
CVE-2021-4439 has been classified as a medium severity vulnerability.
How do I fix CVE-2021-4439?
To fix CVE-2021-4439, upgrade your Linux kernel to a version that is not affected by this vulnerability.
Which Linux kernel versions are affected by CVE-2021-4439?
CVE-2021-4439 affects various versions of the Linux kernel, specifically those between versions 4.4 and 5.15-rc5.
What is the nature of the vulnerability in CVE-2021-4439?
CVE-2021-4439 involves an array index out of bound issue in the isdn cpai component of the Linux kernel.
Is there a workaround for CVE-2021-4439 while waiting for a patch?
No official workaround has been provided for CVE-2021-4439; upgrading the kernel is the recommended approach.
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