linux-kernel - [PATCH] fs/io_uring: fix O_PATH fds in openat, openat2, statx

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Date:   Thu,  7 May 2020 20:57:25 +0200
From:   Max Kellermann <mk@...all.com>
To:     axboe@...nel.dk, linux-fsdevel@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Max Kellermann <mk@...all.com>,
        stable@...r.kernel.org
Subject: [PATCH] fs/io_uring: fix O_PATH fds in openat, openat2, statx

If an operation's flag `needs_file` is set, the function
io_req_set_file() calls io_file_get() to obtain a `struct file*`.

This fails for `O_PATH` file descriptors, because those have no
`struct file*`, causing io_req_set_file() to throw `-EBADF`.  This
breaks the operations `openat`, `openat2` and `statx`, where `O_PATH`
file descriptors are commonly used.

The solution is to simply remove `needs_file` (and the accompanying
flag `fd_non_reg`).  This flag was never needed because those
operations use numeric file descriptor and don't use the `struct
file*` obtained by io_req_set_file().

Signed-off-by: Max Kellermann <mk@...all.com>
Cc: stable@...r.kernel.org
---
 fs/io_uring.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index a46de2cfc28e..d24f8e33323c 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -693,8 +693,6 @@ static const struct io_op_def io_op_defs[] = {
 		.needs_file		= 1,
 	},
 	[IORING_OP_OPENAT] = {
-		.needs_file		= 1,
-		.fd_non_neg		= 1,
 		.file_table		= 1,
 		.needs_fs		= 1,
 	},
@@ -708,8 +706,6 @@ static const struct io_op_def io_op_defs[] = {
 	},
 	[IORING_OP_STATX] = {
 		.needs_mm		= 1,
-		.needs_file		= 1,
-		.fd_non_neg		= 1,
 		.needs_fs		= 1,
 	},
 	[IORING_OP_READ] = {
@@ -739,8 +735,6 @@ static const struct io_op_def io_op_defs[] = {
 		.unbound_nonreg_file	= 1,
 	},
 	[IORING_OP_OPENAT2] = {
-		.needs_file		= 1,
-		.fd_non_neg		= 1,
 		.file_table		= 1,
 		.needs_fs		= 1,
 	},
-- 
2.20.1