[PATCH 1/9] io_uring: fix leaking reg files on exit

Pavel Begunkov
2021-04-13T02:03:06Z

If io_sqe_files_unregister() faults on io_rsrc_ref_quiesce(), it will
fail to do unregister leaving files referenced. And that may well happen
because of a strayed signal or just because it does allocations inside.

In io_ring_ctx_free() do an unsafe version of unregister, as it's
guaranteed to not have requests by that point and so quiesce is useless.

Cc: stable@vger.kernel.org
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
fs/io_uring.c | 29 +++++++++++++++--------------
1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 257eddd4cd82..44342ff5c4e1 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7094,6 +7094,10 @@ static void __io_sqe_files_unregister(struct io_ring_ctx *ctx)
fput(file);
}
#endif
+ io_free_file_tables(&ctx->file_table, ctx->nr_user_files);
+ kfree(ctx->file_data);
+ ctx->file_data = NULL;
+ ctx->nr_user_files = 0;
}

static inline void io_rsrc_ref_lock(struct io_ring_ctx *ctx)
@@ -7200,21 +7204,14 @@ static struct io_rsrc_data *io_rsrc_data_alloc(struct io_ring_ctx *ctx,

static int io_sqe_files_unregister(struct io_ring_ctx *ctx)
{
- struct io_rsrc_data *data = ctx->file_data;
int ret;

- if (!data)
+ if (!ctx->file_data)
return -ENXIO;
- ret = io_rsrc_ref_quiesce(data, ctx);
- if (ret)
- return ret;
-
- __io_sqe_files_unregister(ctx);
- io_free_file_tables(&ctx->file_table, ctx->nr_user_files);
- kfree(data);
- ctx->file_data = NULL;
- ctx->nr_user_files = 0;
- return 0;
+ ret = io_rsrc_ref_quiesce(ctx->file_data, ctx);
+ if (!ret)
+ __io_sqe_files_unregister(ctx);
+ return ret;
}

static void io_sq_thread_unpark(struct io_sq_data *sqd)
@@ -7664,7 +7661,7 @@ static int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg,

ret = io_sqe_files_scm(ctx);
if (ret) {
- io_sqe_files_unregister(ctx);
+ __io_sqe_files_unregister(ctx);
return ret;
}

@@ -8465,7 +8462,11 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx)
}

mutex_lock(&ctx->uring_lock);
- io_sqe_files_unregister(ctx);
+ if (ctx->file_data) {
+ if (!atomic_dec_and_test(&ctx->file_data->refs))
+ wait_for_completion(&ctx->file_data->done);
+ __io_sqe_files_unregister(ctx);
+ }
if (ctx->rings)
__io_cqring_overflow_flush(ctx, true);
mutex_unlock(&ctx->uring_lock);
--
2.24.0