| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <2024052452-CVE-2021-47505-427f@gregkh> Date: Fri, 24 May 2024 17:01:54 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-cve-announce@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org> Subject: CVE-2021-47505: aio: fix use-after-free due to missing POLLFREE handling Description =========== In the Linux kernel, the following vulnerability has been resolved: aio: fix use-after-free due to missing POLLFREE handling signalfd_poll() and binder_poll() are special in that they use a waitqueue whose lifetime is the current task, rather than the struct file as is normally the case. This is okay for blocking polls, since a blocking poll occurs within one task; however, non-blocking polls require another solution. This solution is for the queue to be cleared before it is freed, by sending a POLLFREE notification to all waiters. Unfortunately, only eventpoll handles POLLFREE. A second type of non-blocking poll, aio poll, was added in kernel v4.18, and it doesn't handle POLLFREE. This allows a use-after-free to occur if a signalfd or binder fd is polled with aio poll, and the waitqueue gets freed. Fix this by making aio poll handle POLLFREE. A patch by Ramji Jiyani <ramjiyani@...gle.com> (https://lore.kernel.org/r/20211027011834.2497484-1-ramjiyani@google.com) tried to do this by making aio_poll_wake() always complete the request inline if POLLFREE is seen. However, that solution had two bugs. First, it introduced a deadlock, as it unconditionally locked the aio context while holding the waitqueue lock, which inverts the normal locking order. Second, it didn't consider that POLLFREE notifications are missed while the request has been temporarily de-queued. The second problem was solved by my previous patch. This patch then properly fixes the use-after-free by handling POLLFREE in a deadlock-free way. It does this by taking advantage of the fact that freeing of the waitqueue is RCU-delayed, similar to what eventpoll does. The Linux kernel CVE team has assigned CVE-2021-47505 to this issue. Affected and fixed versions =========================== Issue introduced in 4.18 with commit 2c14fa838cbe and fixed in 4.19.221 with commit 321fba81ec03 Issue introduced in 4.18 with commit 2c14fa838cbe and fixed in 5.4.165 with commit 4105e6a128e8 Issue introduced in 4.18 with commit 2c14fa838cbe and fixed in 5.10.85 with commit 47ffefd88abf Issue introduced in 4.18 with commit 2c14fa838cbe and fixed in 5.15.8 with commit 60d311f9e638 Issue introduced in 4.18 with commit 2c14fa838cbe and fixed in 5.16 with commit 50252e4b5e98 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-2021-47505 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/aio.c include/uapi/asm-generic/poll.h 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/321fba81ec034f88aea4898993c1bf15605c023f https://git.kernel.org/stable/c/4105e6a128e8a98455dfc9e6dbb2ab0c33c4497f https://git.kernel.org/stable/c/47ffefd88abfffe8a040bcc1dd0554d4ea6f7689 https://git.kernel.org/stable/c/60d311f9e6381d779d7d53371f87285698ecee24 https://git.kernel.org/stable/c/50252e4b5e989ce64555c7aef7516bdefc2fea72
Powered by blists - more mailing lists