From 973d2c13b682cb4c3779c5d5a59e021838f4d79f Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@gmail.com>
Date: Sat, 27 Nov 2021 16:29:37 +0800
Subject: [PATCH] io_uring: return back safer resurrect
mainline inclusion
from mainline-v5.13-rc1
commit f70865db5ff35f5ed0c7e9ef63e7cca3d4947f04
category: bugfix
bugzilla: 185739
CVE: NA
-----------------------------------------------
Revert of revert of "io_uring: wait potential ->release() on resurrect",
which adds a helper for resurrect not racing completion reinit, as was
removed because of a strange bug with no clear root or link to the
patch.
Was improved, instead of rcu_synchronize(), just wait_for_completion()
because we're at 0 refs and it will happen very shortly. Specifically
use non-interruptible version to ignore all pending signals that may
have ended prior interruptible wait.
This reverts commit cb5e1b81304e089ee3ca948db4d29f71902eb575.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/7a080c20f686d026efade810b116b72f88abaff9.1618101759.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
conflicts:
fs/io_uring.c
Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
fs/io_uring.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index da61eeaf64e8..d07388600bbe 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8669,6 +8669,18 @@ static bool io_register_op_must_quiesce(int op)
}
}
+static void io_refs_resurrect(struct percpu_ref *ref, struct completion *compl)
+{
+ bool got = percpu_ref_tryget(ref);
+
+ /* already at zero, wait for ->release() */
+ if (!got)
+ wait_for_completion(compl);
+ percpu_ref_resurrect(ref);
+ if (got)
+ percpu_ref_put(ref);
+}
+
static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
void __user *arg, unsigned nr_args)
__releases(ctx->uring_lock)
@@ -8699,9 +8711,8 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
ret = wait_for_completion_interruptible(&ctx->ref_comp);
mutex_lock(&ctx->uring_lock);
if (ret) {
- percpu_ref_resurrect(&ctx->refs);
- ret = -EINTR;
- goto out;
+ io_refs_resurrect(&ctx->refs, &ctx->ref_comp);
+ return ret;
}
}
@@ -8772,7 +8783,6 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
if (io_register_op_must_quiesce(opcode)) {
/* bring the ctx back to life */
percpu_ref_reinit(&ctx->refs);
-out:
reinit_completion(&ctx->ref_comp);
}
return ret;
--
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