6.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jens Axboe axboe@kernel.dk
commit 8b51a3956d44ea6ade962874ade14de9a7d16556 upstream.
If we specify a valid CQ ring address but an invalid SQ ring address, we'll correctly spot this and free the allocated pages and clear them to NULL. However, we don't clear the ring page count, and hence will attempt to free the pages again. We've already cleared the address of the page array when freeing them, but we don't check for that. This causes the following crash:
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 Oops [#1] Modules linked in: CPU: 0 PID: 20 Comm: kworker/u2:1 Not tainted 6.6.0-rc5-dirty #56 Hardware name: ucbbar,riscvemu-bare (DT) Workqueue: events_unbound io_ring_exit_work epc : io_pages_free+0x2a/0x58 ra : io_rings_free+0x3a/0x50 epc : ffffffff808811a2 ra : ffffffff80881406 sp : ffff8f80000c3cd0 status: 0000000200000121 badaddr: 0000000000000000 cause: 000000000000000d [<ffffffff808811a2>] io_pages_free+0x2a/0x58 [<ffffffff80881406>] io_rings_free+0x3a/0x50 [<ffffffff80882176>] io_ring_exit_work+0x37e/0x424 [<ffffffff80027234>] process_one_work+0x10c/0x1f4 [<ffffffff8002756e>] worker_thread+0x252/0x31c [<ffffffff8002f5e4>] kthread+0xc4/0xe0 [<ffffffff8000332a>] ret_from_fork+0xa/0x1c
Check for a NULL array in io_pages_free(), but also clear the page counts when we free them to be on the safer side.
Reported-by: rtm@csail.mit.edu Fixes: 03d89a2de25b ("io_uring: support for user allocated memory for rings/sqes") Cc: stable@vger.kernel.org Reviewed-by: Jeff Moyer jmoyer@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- io_uring/io_uring.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -2666,7 +2666,11 @@ static void io_pages_free(struct page **
if (!pages) return; + page_array = *pages; + if (!page_array) + return; + for (i = 0; i < npages; i++) unpin_user_page(page_array[i]); kvfree(page_array); @@ -2750,7 +2754,9 @@ static void io_rings_free(struct io_ring ctx->sq_sqes = NULL; } else { io_pages_free(&ctx->ring_pages, ctx->n_ring_pages); + ctx->n_ring_pages = 0; io_pages_free(&ctx->sqe_pages, ctx->n_sqe_pages); + ctx->n_sqe_pages = 0; } }