diff options
Diffstat (limited to 'meta-openbmc-mods/meta-common/recipes-kernel/linux/linux-aspeed/CVE-2021-39698.patch')
| -rw-r--r-- | meta-openbmc-mods/meta-common/recipes-kernel/linux/linux-aspeed/CVE-2021-39698.patch | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/meta-openbmc-mods/meta-common/recipes-kernel/linux/linux-aspeed/CVE-2021-39698.patch b/meta-openbmc-mods/meta-common/recipes-kernel/linux/linux-aspeed/CVE-2021-39698.patch new file mode 100644 index 000000000..9a7250566 --- /dev/null +++ b/meta-openbmc-mods/meta-common/recipes-kernel/linux/linux-aspeed/CVE-2021-39698.patch @@ -0,0 +1,107 @@ +From 1ebb6cd8c754bfe1a5f9539027980756bce7cb08 Mon Sep 17 00:00:00 2001 +From: Eric Biggers <ebiggers@google.com> +Date: Wed, 8 Dec 2021 17:04:51 -0800 +Subject: [PATCH] wait: add wake_up_pollfree() + +commit 42288cb44c4b5fff7653bc392b583a2b8bd6a8c0 upstream. + +Several ->poll() implementations 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, using 'wake_up_poll(wq, EPOLLHUP | POLLFREE);'. + +However, that has a bug: wake_up_poll() calls __wake_up() with +nr_exclusive=1. Therefore, if there are multiple "exclusive" waiters, +and the wakeup function for the first one returns a positive value, only +that one will be called. That's *not* what's needed for POLLFREE; +POLLFREE is special in that it really needs to wake up everyone. + +Considering the three non-blocking poll systems: + +- io_uring poll doesn't handle POLLFREE at all, so it is broken anyway. + +- aio poll is unaffected, since it doesn't support exclusive waits. + However, that's fragile, as someone could add this feature later. + +- epoll doesn't appear to be broken by this, since its wakeup function + returns 0 when it sees POLLFREE. But this is fragile. + +Although there is a workaround (see epoll), it's better to define a +function which always sends POLLFREE to all waiters. Add such a +function. Also make it verify that the queue really becomes empty after +all waiters have been woken up. + +Reported-by: Linus Torvalds <torvalds@linux-foundation.org> +Cc: stable@vger.kernel.org +Link: https://lore.kernel.org/r/20211209010455.42744-2-ebiggers@kernel.org +Signed-off-by: Eric Biggers <ebiggers@google.com> +Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> +--- + include/linux/wait.h | 26 ++++++++++++++++++++++++++ + kernel/sched/wait.c | 7 +++++++ + 2 files changed, 33 insertions(+) + +diff --git a/include/linux/wait.h b/include/linux/wait.h +index 93dab0e9580f8d..d22cf2985b8fd6 100644 +--- a/include/linux/wait.h ++++ b/include/linux/wait.h +@@ -217,6 +217,7 @@ void __wake_up_sync_key(struct wait_queue_head *wq_head, unsigned int mode, void + void __wake_up_locked_sync_key(struct wait_queue_head *wq_head, unsigned int mode, void *key); + void __wake_up_locked(struct wait_queue_head *wq_head, unsigned int mode, int nr); + void __wake_up_sync(struct wait_queue_head *wq_head, unsigned int mode); ++void __wake_up_pollfree(struct wait_queue_head *wq_head); + + #define wake_up(x) __wake_up(x, TASK_NORMAL, 1, NULL) + #define wake_up_nr(x, nr) __wake_up(x, TASK_NORMAL, nr, NULL) +@@ -245,6 +246,31 @@ void __wake_up_sync(struct wait_queue_head *wq_head, unsigned int mode); + #define wake_up_interruptible_sync_poll_locked(x, m) \ + __wake_up_locked_sync_key((x), TASK_INTERRUPTIBLE, poll_to_key(m)) + ++/** ++ * wake_up_pollfree - signal that a polled waitqueue is going away ++ * @wq_head: the wait queue head ++ * ++ * In the very rare cases where a ->poll() implementation uses a waitqueue whose ++ * lifetime is tied to a task rather than to the 'struct file' being polled, ++ * this function must be called before the waitqueue is freed so that ++ * non-blocking polls (e.g. epoll) are notified that the queue is going away. ++ * ++ * The caller must also RCU-delay the freeing of the wait_queue_head, e.g. via ++ * an explicit synchronize_rcu() or call_rcu(), or via SLAB_TYPESAFE_BY_RCU. ++ */ ++static inline void wake_up_pollfree(struct wait_queue_head *wq_head) ++{ ++ /* ++ * For performance reasons, we don't always take the queue lock here. ++ * Therefore, we might race with someone removing the last entry from ++ * the queue, and proceed while they still hold the queue lock. ++ * However, rcu_read_lock() is required to be held in such cases, so we ++ * can safely proceed with an RCU-delayed free. ++ */ ++ if (waitqueue_active(wq_head)) ++ __wake_up_pollfree(wq_head); ++} ++ + #define ___wait_cond_timeout(condition) \ + ({ \ + bool __cond = (condition); \ +diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c +index 76577d1642a5dc..eca38107b32f16 100644 +--- a/kernel/sched/wait.c ++++ b/kernel/sched/wait.c +@@ -238,6 +238,13 @@ void __wake_up_sync(struct wait_queue_head *wq_head, unsigned int mode) + } + EXPORT_SYMBOL_GPL(__wake_up_sync); /* For internal use only */ + ++void __wake_up_pollfree(struct wait_queue_head *wq_head) ++{ ++ __wake_up(wq_head, TASK_NORMAL, 0, poll_to_key(EPOLLHUP | POLLFREE)); ++ /* POLLFREE must have cleared the queue. */ ++ WARN_ON_ONCE(waitqueue_active(wq_head)); ++} ++ + /* + * Note: we use "set_current_state()" _after_ the wait-queue add, + * because we need a memory barrier there on SMP, so that any |