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io_uring: disallow close of ring itself 

A previous commit enabled this functionality, which also enabled O_PATH
to work correctly with io_uring. But we can't safely close the ring
itself, as the file handle isn't reference counted inside
io_uring_enter(). Instead of jumping through hoops to enable ring
closure, add a "soft" ->needs_file option, ->needs_file_no_error. This
enables O_PATH file descriptors to work, but still catches the case of
trying to close the ring itself.

Reported-by: Jann Horn <jannh@google.com>
Fixes: 904fbcb115 ("io_uring: remove 'fd is io_uring' from close path")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2020-06-02 16:40:47 -06:00
parent 1ee08de1e2
commit fd2206e4e9
1 changed files with 17 additions and 8 deletions
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25
fs/io_uring.c
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@ -698,6 +698,8 @@ struct io_op_def {
unsigned needs_mm : 1;
/* needs req->file assigned */
unsigned needs_file : 1;
/* don't fail if file grab fails */
unsigned needs_file_no_error : 1;
/* hash wq insertion if file is a regular file */
unsigned hash_reg_file : 1;
/* unbound wq insertion if file is a non-regular file */
@ -804,6 +806,8 @@ static const struct io_op_def io_op_defs[] = {
.needs_fs = 1,
},
[IORING_OP_CLOSE] = {
.needs_file = 1,
.needs_file_no_error = 1,
.file_table = 1,
},
[IORING_OP_FILES_UPDATE] = {
@ -3421,6 +3425,10 @@ static int io_close_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
return -EBADF;
req->close.fd = READ_ONCE(sqe->fd);
if ((req->file && req->file->f_op == &io_uring_fops) ||
req->close.fd == req->ctx->ring_fd)
return -EBADF;
return 0;
}
@ -5438,19 +5446,20 @@ static int io_file_get(struct io_submit_state *state, struct io_kiocb *req,
return -EBADF;
fd = array_index_nospec(fd, ctx->nr_user_files);
file = io_file_from_index(ctx, fd);
if (!file)
return -EBADF;
req->fixed_file_refs = ctx->file_data->cur_refs;
percpu_ref_get(req->fixed_file_refs);
if (file) {
req->fixed_file_refs = ctx->file_data->cur_refs;
percpu_ref_get(req->fixed_file_refs);
}
} else {
trace_io_uring_file_get(ctx, fd);
file = __io_file_get(state, fd);
if (unlikely(!file))
return -EBADF;
}
*out_file = file;
return 0;
if (file || io_op_defs[req->opcode].needs_file_no_error) {
*out_file = file;
return 0;
}
return -EBADF;
}
static int io_req_set_file(struct io_submit_state *state, struct io_kiocb *req,