| 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-2021-47280: drm: Fix use-after-free read in drm_getunique() |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| drm: Fix use-after-free read in drm_getunique() |
| |
| There is a time-of-check-to-time-of-use error in drm_getunique() due |
| to retrieving file_priv->master prior to locking the device's master |
| mutex. |
| |
| An example can be seen in the crash report of the use-after-free error |
| found by Syzbot: |
| https://syzkaller.appspot.com/bug?id=148d2f1dfac64af52ffd27b661981a540724f803 |
| |
| In the report, the master pointer was used after being freed. This is |
| because another process had acquired the device's master mutex in |
| drm_setmaster_ioctl(), then overwrote fpriv->master in |
| drm_new_set_master(). The old value of fpriv->master was subsequently |
| freed before the mutex was unlocked. |
| |
| To fix this, we lock the device's master mutex before retrieving the |
| pointer from from fpriv->master. This patch passes the Syzbot |
| reproducer test. |
| |
| The Linux kernel CVE team has assigned CVE-2021-47280 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Fixed in 4.14.237 with commit 17dab9326ff263c62dab1dbac4492e2938a049e4 |
| Fixed in 4.19.195 with commit 7d233ba700ceb593905ea82b42dadb4ec8ef85e9 |
| Fixed in 5.4.126 with commit b246b4c70c1250e7814f409b243000f9c0bf79a3 |
| Fixed in 5.10.44 with commit 491d52e0078860b33b6c14f0a7ac74ca1b603bd6 |
| Fixed in 5.12.11 with commit f773f8cccac13c7e7bbd9182e7996c727742488e |
| Fixed in 5.13 with commit b436acd1cf7fac0ba987abd22955d98025c80c2b |
| |
| 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-2021-47280 |
| 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/gpu/drm/drm_ioctl.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/17dab9326ff263c62dab1dbac4492e2938a049e4 |
| https://git.kernel.org/stable/c/7d233ba700ceb593905ea82b42dadb4ec8ef85e9 |
| https://git.kernel.org/stable/c/b246b4c70c1250e7814f409b243000f9c0bf79a3 |
| https://git.kernel.org/stable/c/491d52e0078860b33b6c14f0a7ac74ca1b603bd6 |
| https://git.kernel.org/stable/c/f773f8cccac13c7e7bbd9182e7996c727742488e |
| https://git.kernel.org/stable/c/b436acd1cf7fac0ba987abd22955d98025c80c2b |
