linux-kernel - [PATCH V1] fuse: Set fuse request error upon fuse abort connection

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Message-Id: <1618582752-26178-1-git-send-email-pragalla@codeaurora.org>
Date:   Fri, 16 Apr 2021 19:49:12 +0530
From:   Pradeep P V K <pragalla@...eaurora.org>
To:     miklos@...redi.hu
Cc:     stummala@...eaurora.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        Pradeep P V K <pragalla@...eaurora.org>
Subject: [PATCH V1] fuse: Set fuse request error upon fuse abort connection

There is a minor race in setting the fuse out request error
between fuse_abort_conn() and fuse_dev_do_read() as explained
below.

Thread-1			  Thread-2
========			  ========
->fuse_simple_request()           ->shutdown
  ->__fuse_request_send()
    ->queue_request()		->fuse_abort_conn()
->fuse_dev_do_read()                ->acquire(fpq->lock)
  ->wait_for(fpq->lock) 	  ->set err to all req's in fpq->io
				  ->release(fpq->lock)
  ->acquire(fpq->lock)
  ->add req to fpq->io

The above scenario may cause Thread-1 request to add into
fpq->io list after Thread-2 sets -ECONNABORTED err to all
its requests in fpq->io list. This leaves Thread-1 request
with unset err and this further misleads as a completed
request without an err set upon request_end().

Handle this by setting the err appropriately.

Signed-off-by: Pradeep P V K <pragalla@...eaurora.org>
---
 fs/fuse/dev.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index a5ceccc..102c56f 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1283,6 +1283,7 @@ static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file,
 	clear_bit(FR_LOCKED, &req->flags);
 	if (!fpq->connected) {
 		err = fc->aborted ? -ECONNABORTED : -ENODEV;
+		req->out.h.error = err;
 		goto out_end;
 	}
 	if (err) {
-- 
2.7.4