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io_uring: don't rely on weak ->files references

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Grab actual references to the files_struct. To avoid circular references
issues due to this, we add a per-task note that keeps track of what
io_uring contexts a task has used. When the tasks execs or exits its
assigned files, we cancel requests based on this tracking.

With that, we can grab proper references to the files table, and no
longer need to rely on stashing away ring_fd and ring_file to check
if the ring_fd may have been closed.

Cc: stable@vger.kernel.org # v5.5+
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe
2020-09-13 13:09:39 -06:00
parent e6c8aa9ac3
commit 0f2122045b
7 changed files with 344 additions and 37 deletions
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6
kernel/fork.c
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@@ -95,6 +95,7 @@
#include <linux/stackleak.h>
#include <linux/kasan.h>
#include <linux/scs.h>
#include <linux/io_uring.h>
#include <asm/pgalloc.h>
#include <linux/uaccess.h>
@@ -728,6 +729,7 @@ void __put_task_struct(struct task_struct *tsk)
WARN_ON(refcount_read(&tsk->usage));
WARN_ON(tsk == current);
io_uring_free(tsk);
cgroup_free(tsk);
task_numa_free(tsk, true);
security_task_free(tsk);
@@ -1983,6 +1985,10 @@ static __latent_entropy struct task_struct *copy_process(
p->vtime.state = VTIME_INACTIVE;
#endif
#ifdef CONFIG_IO_URING
p->io_uring = NULL;
#endif
#if defined(SPLIT_RSS_COUNTING)
memset(&p->rss_stat, 0, sizeof(p->rss_stat));
#endif