netdev - [PATCH 1/8] aio: make sure file is pinned

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Message-Id: <20190307000316.31133-1-viro@ZenIV.linux.org.uk>
Date:   Thu,  7 Mar 2019 00:03:09 +0000
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        David Miller <davem@...emloft.net>,
        Jason Baron <jbaron@...mai.com>, kgraul@...ux.ibm.com,
        ktkhai@...tuozzo.com, kyeongdon.kim@....com,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>, pabeni@...hat.com,
        syzkaller-bugs@...glegroups.com, xiyou.wangcong@...il.com,
        Christoph Hellwig <hch@....de>,
        zhengbin <zhengbin13@...wei.com>, bcrl@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-aio@...ck.org,
        houtao1@...wei.com, yi.zhang@...wei.com
Subject: [PATCH 1/8] aio: make sure file is pinned

From: Al Viro <viro@...iv.linux.org.uk>

"aio: remove the extra get_file/fput pair in io_submit_one" was
too optimistic - not dereferencing file pointer after e.g.
->write_iter() returns is not enough; that reference might've been
the only thing that kept alive objects that are referenced
*before* the method returns.  Such as inode, for example...

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 fs/aio.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/aio.c b/fs/aio.c
index 3d9669d011b9..ea30b78187ed 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1790,6 +1790,7 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb,
 			   struct iocb __user *user_iocb, bool compat)
 {
 	struct aio_kiocb *req;
+	struct file *file;
 	ssize_t ret;
 
 	/* enforce forwards compatibility on users */
@@ -1844,6 +1845,7 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb,
 
 	req->ki_user_iocb = user_iocb;
 	req->ki_user_data = iocb->aio_data;
+	file = get_file(req->ki_filp);	/* req can die too early */
 
 	switch (iocb->aio_lio_opcode) {
 	case IOCB_CMD_PREAD:
@@ -1872,6 +1874,7 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb,
 		ret = -EINVAL;
 		break;
 	}
+	fput(file);
 
 	/*
 	 * If ret is 0, we'd either done aio_complete() ourselves or have
-- 
2.11.0