io_uring: fix file leak on error path of io ctx creationio_uring-5.10-2020-12-11

Put file as part of error handling when setting up io ctx to fix
memory leaks like the following one.

   BUG: memory leak
   unreferenced object 0xffff888101ea2200 (size 256):
     comm "syz-executor355", pid 8470, jiffies 4294953658 (age 32.400s)
     hex dump (first 32 bytes):
       00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
       20 59 03 01 81 88 ff ff 80 87 a8 10 81 88 ff ff   Y..............
     backtrace:
       [<000000002e0a7c5f>] kmem_cache_zalloc include/linux/slab.h:654 [inline]
       [<000000002e0a7c5f>] __alloc_file+0x1f/0x130 fs/file_table.c:101
       [<000000001a55b73a>] alloc_empty_file+0x69/0x120 fs/file_table.c:151
       [<00000000fb22349e>] alloc_file+0x33/0x1b0 fs/file_table.c:193
       [<000000006e1465bb>] alloc_file_pseudo+0xb2/0x140 fs/file_table.c:233
       [<000000007118092a>] anon_inode_getfile fs/anon_inodes.c:91 [inline]
       [<000000007118092a>] anon_inode_getfile+0xaa/0x120 fs/anon_inodes.c:74
       [<000000002ae99012>] io_uring_get_fd fs/io_uring.c:9198 [inline]
       [<000000002ae99012>] io_uring_create fs/io_uring.c:9377 [inline]
       [<000000002ae99012>] io_uring_setup+0x1125/0x1630 fs/io_uring.c:9411
       [<000000008280baad>] do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
       [<00000000685d8cf0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported-by: syzbot+71c4697e27c99fddcf17@syzkaller.appspotmail.com
Fixes: 0f2122045b94 ("io_uring: don't rely on weak ->files references")
Cc: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Hillf Danton <hdanton@sina.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 10 insertions, 7 deletions

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 908817cea4f5..86dac2b2e276 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -9183,6 +9183,7 @@ static int io_uring_get_fd(struct io_ring_ctx *ctx)
 {
 	struct file *file;
 	int ret;
+	int fd;
 
 #if defined(CONFIG_UNIX)
 	ret = sock_create_kern(&init_net, PF_UNIX, SOCK_RAW, IPPROTO_IP,
@@ -9194,12 +9195,12 @@ static int io_uring_get_fd(struct io_ring_ctx *ctx)
 	ret = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
 	if (ret < 0)
 		goto err;
+	fd = ret;
 
 	file = anon_inode_getfile("[io_uring]", &io_uring_fops, ctx,
 					O_RDWR | O_CLOEXEC);
 	if (IS_ERR(file)) {
-err_fd:
-		put_unused_fd(ret);
+		put_unused_fd(fd);
 		ret = PTR_ERR(file);
 		goto err;
 	}
@@ -9207,12 +9208,14 @@ err_fd:
 #if defined(CONFIG_UNIX)
 	ctx->ring_sock->file = file;
 #endif
-	if (unlikely(io_uring_add_task_file(ctx, file))) {
-		file = ERR_PTR(-ENOMEM);
-		goto err_fd;
+	ret = io_uring_add_task_file(ctx, file);
+	if (ret) {
+		fput(file);
+		put_unused_fd(fd);
+		goto err;
 	}
-	fd_install(ret, file);
-	return ret;
+	fd_install(fd, file);
+	return fd;
 err:
 #if defined(CONFIG_UNIX)
 	sock_release(ctx->ring_sock);