| 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-2022-49327: bcache: avoid journal no-space deadlock by reserving 1 journal bucket |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| bcache: avoid journal no-space deadlock by reserving 1 journal bucket |
| |
| The journal no-space deadlock was reported time to time. Such deadlock |
| can happen in the following situation. |
| |
| When all journal buckets are fully filled by active jset with heavy |
| write I/O load, the cache set registration (after a reboot) will load |
| all active jsets and inserting them into the btree again (which is |
| called journal replay). If a journaled bkey is inserted into a btree |
| node and results btree node split, new journal request might be |
| triggered. For example, the btree grows one more level after the node |
| split, then the root node record in cache device super block will be |
| upgrade by bch_journal_meta() from bch_btree_set_root(). But there is no |
| space in journal buckets, the journal replay has to wait for new journal |
| bucket to be reclaimed after at least one journal bucket replayed. This |
| is one example that how the journal no-space deadlock happens. |
| |
| The solution to avoid the deadlock is to reserve 1 journal bucket in |
| run time, and only permit the reserved journal bucket to be used during |
| cache set registration procedure for things like journal replay. Then |
| the journal space will never be fully filled, there is no chance for |
| journal no-space deadlock to happen anymore. |
| |
| This patch adds a new member "bool do_reserve" in struct journal, it is |
| inititalized to 0 (false) when struct journal is allocated, and set to |
| 1 (true) by bch_journal_space_reserve() when all initialization done in |
| run_cache_set(). In the run time when journal_reclaim() tries to |
| allocate a new journal bucket, free_journal_buckets() is called to check |
| whether there are enough free journal buckets to use. If there is only |
| 1 free journal bucket and journal->do_reserve is 1 (true), the last |
| bucket is reserved and free_journal_buckets() will return 0 to indicate |
| no free journal bucket. Then journal_reclaim() will give up, and try |
| next time to see whetheer there is free journal bucket to allocate. By |
| this method, there is always 1 jouranl bucket reserved in run time. |
| |
| During the cache set registration, journal->do_reserve is 0 (false), so |
| the reserved journal bucket can be used to avoid the no-space deadlock. |
| |
| The Linux kernel CVE team has assigned CVE-2022-49327 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Fixed in 5.10.121 with commit 59afd4f287900c8187e968a4153ed35e6b48efce |
| Fixed in 5.15.46 with commit 5607652823ac65e2c6885e73bd46d5a4f9a20363 |
| Fixed in 5.17.14 with commit 6332ea3e35efa12dc08f0cbf5faea5e6e8eb0497 |
| Fixed in 5.18.3 with commit 1dda32aed6f62c163f38ff947ef5b3360e329159 |
| Fixed in 5.19 with commit 32feee36c30ea06e38ccb8ae6e5c44c6eec790a6 |
| |
| 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-2022-49327 |
| 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/md/bcache/journal.c |
| drivers/md/bcache/journal.h |
| drivers/md/bcache/super.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/59afd4f287900c8187e968a4153ed35e6b48efce |
| https://git.kernel.org/stable/c/5607652823ac65e2c6885e73bd46d5a4f9a20363 |
| https://git.kernel.org/stable/c/6332ea3e35efa12dc08f0cbf5faea5e6e8eb0497 |
| https://git.kernel.org/stable/c/1dda32aed6f62c163f38ff947ef5b3360e329159 |
| https://git.kernel.org/stable/c/32feee36c30ea06e38ccb8ae6e5c44c6eec790a6 |
