Patch "io_uring: statx must grab the file table for valid fd" has been added to the 5.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    io_uring: statx must grab the file table for valid fd

to the 5.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     io_uring-statx-must-grab-the-file-table-for-valid-fd.patch
and it can be found in the queue-5.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit f47f6482ce6dc0bccde2ed5feb274ac38eb6707d
Author: Jens Axboe <axboe@xxxxxxxxx>
Date:   Mon Apr 27 10:41:22 2020 -0600

    io_uring: statx must grab the file table for valid fd
    
    commit 5b0bbee4732cbd58aa98213d4c11a366356bba3d upstream.
    
    Clay reports that OP_STATX fails for a test case with a valid fd
    and empty path:
    
     -- Test 0: statx:fd 3: SUCCEED, file mode 100755
     -- Test 1: statx:path ./uring_statx: SUCCEED, file mode 100755
     -- Test 2: io_uring_statx:fd 3: FAIL, errno 9: Bad file descriptor
     -- Test 3: io_uring_statx:path ./uring_statx: SUCCEED, file mode 100755
    
    This is due to statx not grabbing the process file table, hence we can't
    lookup the fd in async context. If the fd is valid, ensure that we grab
    the file table so we can grab the file from async context.
    
    Cc: stable@xxxxxxxxxxxxxxx # v5.6
    Reported-by: Clay Harris <bugs@xxxxxxxxxxx>
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index a46de2cfc28e8..38b25f5998965 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -479,6 +479,7 @@ enum {
 	REQ_F_COMP_LOCKED_BIT,
 	REQ_F_NEED_CLEANUP_BIT,
 	REQ_F_OVERFLOW_BIT,
+	REQ_F_NO_FILE_TABLE_BIT,
 };
 
 enum {
@@ -521,6 +522,8 @@ enum {
 	REQ_F_NEED_CLEANUP	= BIT(REQ_F_NEED_CLEANUP_BIT),
 	/* in overflow list */
 	REQ_F_OVERFLOW		= BIT(REQ_F_OVERFLOW_BIT),
+	/* doesn't need file table for this request */
+	REQ_F_NO_FILE_TABLE	= BIT(REQ_F_NO_FILE_TABLE_BIT),
 };
 
 /*
@@ -711,6 +714,7 @@ static const struct io_op_def io_op_defs[] = {
 		.needs_file		= 1,
 		.fd_non_neg		= 1,
 		.needs_fs		= 1,
+		.file_table		= 1,
 	},
 	[IORING_OP_READ] = {
 		.needs_mm		= 1,
@@ -2843,8 +2847,12 @@ static int io_statx(struct io_kiocb *req, struct io_kiocb **nxt,
 	struct kstat stat;
 	int ret;
 
-	if (force_nonblock)
+	if (force_nonblock) {
+		/* only need file table for an actual valid fd */
+		if (ctx->dfd == -1 || ctx->dfd == AT_FDCWD)
+			req->flags |= REQ_F_NO_FILE_TABLE;
 		return -EAGAIN;
+	}
 
 	if (vfs_stat_set_lookup_flags(&lookup_flags, ctx->how.flags))
 		return -EINVAL;
@@ -4632,7 +4640,7 @@ static int io_grab_files(struct io_kiocb *req)
 	int ret = -EBADF;
 	struct io_ring_ctx *ctx = req->ctx;
 
-	if (req->work.files)
+	if (req->work.files || (req->flags & REQ_F_NO_FILE_TABLE))
 		return 0;
 	if (!ctx->ring_file)
 		return -EBADF;