--- /dev/null
+From 9ed3208a86d2fc665c9627e367838dc8e779a79e Mon Sep 17 00:00:00 2001
+From: Jens Axboe <axboe@kernel.dk>
+Date: Sat, 1 Jun 2024 12:25:35 -0600
+Subject: io_uring: check for non-NULL file pointer in io_file_can_poll()
+
+From: Jens Axboe <axboe@kernel.dk>
+
+commit 5fc16fa5f13b3c06fdb959ef262050bd810416a2 upstream.
+
+In earlier kernels, it was possible to trigger a NULL pointer
+dereference off the forced async preparation path, if no file had
+been assigned. The trace leading to that looks as follows:
+
+BUG: kernel NULL pointer dereference, address: 00000000000000b0
+PGD 0 P4D 0
+Oops: 0000 [#1] PREEMPT SMP
+CPU: 67 PID: 1633 Comm: buf-ring-invali Not tainted 6.8.0-rc3+ #1
+Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS unknown 2/2/2022
+RIP: 0010:io_buffer_select+0xc3/0x210
+Code: 00 00 48 39 d1 0f 82 ae 00 00 00 48 81 4b 48 00 00 01 00 48 89 73 70 0f b7 50 0c 66 89 53 42 85 ed 0f 85 d2 00 00 00 48 8b 13 <48> 8b 92 b0 00 00 00 48 83 7a 40 00 0f 84 21 01 00 00 4c 8b 20 5b
+RSP: 0018:ffffb7bec38c7d88 EFLAGS: 00010246
+RAX: ffff97af2be61000 RBX: ffff97af234f1700 RCX: 0000000000000040
+RDX: 0000000000000000 RSI: ffff97aecfb04820 RDI: ffff97af234f1700
+RBP: 0000000000000000 R08: 0000000000200030 R09: 0000000000000020
+R10: ffffb7bec38c7dc8 R11: 000000000000c000 R12: ffffb7bec38c7db8
+R13: ffff97aecfb05800 R14: ffff97aecfb05800 R15: ffff97af2be5e000
+FS: 00007f852f74b740(0000) GS:ffff97b1eeec0000(0000) knlGS:0000000000000000
+CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
+CR2: 00000000000000b0 CR3: 000000016deab005 CR4: 0000000000370ef0
+Call Trace:
+ <TASK>
+ ? __die+0x1f/0x60
+ ? page_fault_oops+0x14d/0x420
+ ? do_user_addr_fault+0x61/0x6a0
+ ? exc_page_fault+0x6c/0x150
+ ? asm_exc_page_fault+0x22/0x30
+ ? io_buffer_select+0xc3/0x210
+ __io_import_iovec+0xb5/0x120
+ io_readv_prep_async+0x36/0x70
+ io_queue_sqe_fallback+0x20/0x260
+ io_submit_sqes+0x314/0x630
+ __do_sys_io_uring_enter+0x339/0xbc0
+ ? __do_sys_io_uring_register+0x11b/0xc50
+ ? vm_mmap_pgoff+0xce/0x160
+ do_syscall_64+0x5f/0x180
+ entry_SYSCALL_64_after_hwframe+0x46/0x4e
+RIP: 0033:0x55e0a110a67e
+Code: ba cc 00 00 00 45 31 c0 44 0f b6 92 d0 00 00 00 31 d2 41 b9 08 00 00 00 41 83 e2 01 41 c1 e2 04 41 09 c2 b8 aa 01 00 00 0f 05 <c3> 90 89 30 eb a9 0f 1f 40 00 48 8b 42 20 8b 00 a8 06 75 af 85 f6
+
+because the request is marked forced ASYNC and has a bad file fd, and
+hence takes the forced async prep path.
+
+Current kernels with the request async prep cleaned up can no longer hit
+this issue, but for ease of backporting, let's add this safety check in
+here too as it really doesn't hurt. For both cases, this will inevitably
+end with a CQE posted with -EBADF.
+
+Cc: stable@vger.kernel.org
+Fixes: a76c0b31eef5 ("io_uring: commit non-pollable provided mapped buffers upfront")
+Signed-off-by: Jens Axboe <axboe@kernel.dk>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ io_uring/kbuf.c | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+--- a/io_uring/kbuf.c
++++ b/io_uring/kbuf.c
+@@ -154,7 +154,8 @@ static void __user *io_ring_buffer_selec
+ req->buf_list = bl;
+ req->buf_index = buf->bid;
+
+- if (issue_flags & IO_URING_F_UNLOCKED || !file_can_poll(req->file)) {
++ if (issue_flags & IO_URING_F_UNLOCKED ||
++ (req->file && !file_can_poll(req->file))) {
+ /*
+ * If we came in unlocked, we have no choice but to consume the
+ * buffer here, otherwise nothing ensures that the buffer won't