| 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-2021-46935: binder: fix async_free_space accounting for empty parcels |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| binder: fix async_free_space accounting for empty parcels |
| |
| In 4.13, commit 74310e06be4d ("android: binder: Move buffer out of area shared with user space") |
| fixed a kernel structure visibility issue. As part of that patch, |
| sizeof(void *) was used as the buffer size for 0-length data payloads so |
| the driver could detect abusive clients sending 0-length asynchronous |
| transactions to a server by enforcing limits on async_free_size. |
| |
| Unfortunately, on the "free" side, the accounting of async_free_space |
| did not add the sizeof(void *) back. The result was that up to 8-bytes of |
| async_free_space were leaked on every async transaction of 8-bytes or |
| less. These small transactions are uncommon, so this accounting issue |
| has gone undetected for several years. |
| |
| The fix is to use "buffer_size" (the allocated buffer size) instead of |
| "size" (the logical buffer size) when updating the async_free_space |
| during the free operation. These are the same except for this |
| corner case of asynchronous transactions with payloads < 8 bytes. |
| |
| The Linux kernel CVE team has assigned CVE-2021-46935 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 4.14 with commit 74310e06be4d74dcf67cd108366710dee5c576d5 and fixed in 4.14.261 with commit 2d2df539d05205fd83c404d5f2dff48d36f9b495 |
| Issue introduced in 4.14 with commit 74310e06be4d74dcf67cd108366710dee5c576d5 and fixed in 4.19.224 with commit 7c7064402609aeb6fb11be1b4ec10673ff17b593 |
| Issue introduced in 4.14 with commit 74310e06be4d74dcf67cd108366710dee5c576d5 and fixed in 5.4.170 with commit 103b16a8c51f96d5fe063022869ea906c256e5da |
| Issue introduced in 4.14 with commit 74310e06be4d74dcf67cd108366710dee5c576d5 and fixed in 5.10.90 with commit 1cb8444f3114f0bb2f6e3bcadcf09aa4a28425d4 |
| Issue introduced in 4.14 with commit 74310e06be4d74dcf67cd108366710dee5c576d5 and fixed in 5.15.13 with commit 17691bada6b2f1d5f1c0f6d28cd9d0727023b0ff |
| Issue introduced in 4.14 with commit 74310e06be4d74dcf67cd108366710dee5c576d5 and fixed in 5.16 with commit cfd0d84ba28c18b531648c9d4a35ecca89ad9901 |
| |
| 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-2021-46935 |
| 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/android/binder_alloc.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/2d2df539d05205fd83c404d5f2dff48d36f9b495 |
| https://git.kernel.org/stable/c/7c7064402609aeb6fb11be1b4ec10673ff17b593 |
| https://git.kernel.org/stable/c/103b16a8c51f96d5fe063022869ea906c256e5da |
| https://git.kernel.org/stable/c/1cb8444f3114f0bb2f6e3bcadcf09aa4a28425d4 |
| https://git.kernel.org/stable/c/17691bada6b2f1d5f1c0f6d28cd9d0727023b0ff |
| https://git.kernel.org/stable/c/cfd0d84ba28c18b531648c9d4a35ecca89ad9901 |
