| 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-2021-47365: afs: Fix page leak |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| afs: Fix page leak |
| |
| There's a loop in afs_extend_writeback() that adds extra pages to a write |
| we want to make to improve the efficiency of the writeback by making it |
| larger. This loop stops, however, if we hit a page we can't write back |
| from immediately, but it doesn't get rid of the page ref we speculatively |
| acquired. |
| |
| This was caused by the removal of the cleanup loop when the code switched |
| from using find_get_pages_contig() to xarray scanning as the latter only |
| gets a single page at a time, not a batch. |
| |
| Fix this by putting the page on a ref on an early break from the loop. |
| Unfortunately, we can't just add that page to the pagevec we're employing |
| as we'll go through that and add those pages to the RPC call. |
| |
| This was found by the generic/074 test. It leaks ~4GiB of RAM each time it |
| is run - which can be observed with "top". |
| |
| The Linux kernel CVE team has assigned CVE-2021-47365 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.13 with commit e87b03f5830ecd8ca21836d3ee48c74f8d58fa31 and fixed in 5.14.9 with commit d130b5fdd42254d92948d06347940276140c927e |
| Issue introduced in 5.13 with commit e87b03f5830ecd8ca21836d3ee48c74f8d58fa31 and fixed in 5.15 with commit 581b2027af0018944ba301d68e7af45c6d1128b5 |
| |
| 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-2021-47365 |
| 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: |
| fs/afs/write.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/d130b5fdd42254d92948d06347940276140c927e |
| https://git.kernel.org/stable/c/581b2027af0018944ba301d68e7af45c6d1128b5 |
