| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2021-47185: tty: tty_buffer: Fix the softlockup issue in flush_to_ldisc |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| tty: tty_buffer: Fix the softlockup issue in flush_to_ldisc |
| |
| When running ltp testcase(ltp/testcases/kernel/pty/pty04.c) with arm64, there is a soft lockup, |
| which look like this one: |
| |
| Workqueue: events_unbound flush_to_ldisc |
| Call trace: |
| dump_backtrace+0x0/0x1ec |
| show_stack+0x24/0x30 |
| dump_stack+0xd0/0x128 |
| panic+0x15c/0x374 |
| watchdog_timer_fn+0x2b8/0x304 |
| __run_hrtimer+0x88/0x2c0 |
| __hrtimer_run_queues+0xa4/0x120 |
| hrtimer_interrupt+0xfc/0x270 |
| arch_timer_handler_phys+0x40/0x50 |
| handle_percpu_devid_irq+0x94/0x220 |
| __handle_domain_irq+0x88/0xf0 |
| gic_handle_irq+0x84/0xfc |
| el1_irq+0xc8/0x180 |
| slip_unesc+0x80/0x214 [slip] |
| tty_ldisc_receive_buf+0x64/0x80 |
| tty_port_default_receive_buf+0x50/0x90 |
| flush_to_ldisc+0xbc/0x110 |
| process_one_work+0x1d4/0x4b0 |
| worker_thread+0x180/0x430 |
| kthread+0x11c/0x120 |
| |
| In the testcase pty04, The first process call the write syscall to send |
| data to the pty master. At the same time, the workqueue will do the |
| flush_to_ldisc to pop data in a loop until there is no more data left. |
| When the sender and workqueue running in different core, the sender sends |
| data fastly in full time which will result in workqueue doing work in loop |
| for a long time and occuring softlockup in flush_to_ldisc with kernel |
| configured without preempt. So I add need_resched check and cond_resched |
| in the flush_to_ldisc loop to avoid it. |
| |
| The Linux kernel CVE team has assigned CVE-2021-47185 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Fixed in 4.4.293 with commit 0380f643f3a7a61b0845cdc738959c2ad5735d61 |
| Fixed in 4.9.291 with commit b1ffc16ec05ae40d82b6e373322d62e9d6b54fbc |
| Fixed in 4.14.256 with commit 4c1623651a0936ee197859824cdae6ebbd04d3ed |
| Fixed in 4.19.218 with commit 4f300f47dbcf9c3d4b2ea76c8554c8f360400725 |
| Fixed in 5.4.162 with commit d491c84df5c469dd9621863b6a770b3428137063 |
| Fixed in 5.10.82 with commit 77e9fed33056f2a88eba9dd4d2d5412f0c7d1f41 |
| Fixed in 5.15.5 with commit 5c34486f04700f1ba04907231dce0cc2705c2d7d |
| Fixed in 5.16 with commit 3968ddcf05fb4b9409cd1859feb06a5b0550a1c1 |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2021-47185 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| drivers/tty/tty_buffer.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/0380f643f3a7a61b0845cdc738959c2ad5735d61 |
| https://git.kernel.org/stable/c/b1ffc16ec05ae40d82b6e373322d62e9d6b54fbc |
| https://git.kernel.org/stable/c/4c1623651a0936ee197859824cdae6ebbd04d3ed |
| https://git.kernel.org/stable/c/4f300f47dbcf9c3d4b2ea76c8554c8f360400725 |
| https://git.kernel.org/stable/c/d491c84df5c469dd9621863b6a770b3428137063 |
| https://git.kernel.org/stable/c/77e9fed33056f2a88eba9dd4d2d5412f0c7d1f41 |
| https://git.kernel.org/stable/c/5c34486f04700f1ba04907231dce0cc2705c2d7d |
| https://git.kernel.org/stable/c/3968ddcf05fb4b9409cd1859feb06a5b0550a1c1 |
