6.12-stable review patch. If anyone has any objections, please let me know.
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From: Jens Axboe axboe@kernel.dk
[ Upstream commit c6e60a0a68b7e6b3c7e33863a16e8e88ba9eee6f ]
syzbot reports that ->msg_inq may get used uinitialized from the following path:
BUG: KMSAN: uninit-value in io_recv_buf_select io_uring/net.c:1094 [inline] BUG: KMSAN: uninit-value in io_recv+0x930/0x1f90 io_uring/net.c:1158 io_recv_buf_select io_uring/net.c:1094 [inline] io_recv+0x930/0x1f90 io_uring/net.c:1158 io_issue_sqe+0x420/0x2130 io_uring/io_uring.c:1740 io_queue_sqe io_uring/io_uring.c:1950 [inline] io_req_task_submit+0xfa/0x1d0 io_uring/io_uring.c:1374 io_handle_tw_list+0x55f/0x5c0 io_uring/io_uring.c:1057 tctx_task_work_run+0x109/0x3e0 io_uring/io_uring.c:1121 tctx_task_work+0x6d/0xc0 io_uring/io_uring.c:1139 task_work_run+0x268/0x310 kernel/task_work.c:239 io_run_task_work+0x43a/0x4a0 io_uring/io_uring.h:343 io_cqring_wait io_uring/io_uring.c:2527 [inline] __do_sys_io_uring_enter io_uring/io_uring.c:3439 [inline] __se_sys_io_uring_enter+0x204f/0x4ce0 io_uring/io_uring.c:3330 __x64_sys_io_uring_enter+0x11f/0x1a0 io_uring/io_uring.c:3330 x64_sys_call+0xce5/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:427 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f
and it is correct, as it's never initialized upfront. Hence the first submission can end up using it uninitialized, if the recv wasn't successful and the networking stack didn't honor ->msg_get_inq being set and filling in the output value of ->msg_inq as requested.
Set it to 0 upfront when it's allocated, just to silence this KMSAN warning. There's no side effect of using it uninitialized, it'll just potentially cause the next receive to use a recv value hint that's not accurate.
Fixes: c6f32c7d9e09 ("io_uring/net: get rid of ->prep_async() for receive side") Reported-by: syzbot+068ff190354d2f74892f@syzkaller.appspotmail.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- io_uring/net.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/io_uring/net.c b/io_uring/net.c index 18507658a921..7f549be9abd1 100644 --- a/io_uring/net.c +++ b/io_uring/net.c @@ -748,6 +748,7 @@ static int io_recvmsg_prep_setup(struct io_kiocb *req) if (req->opcode == IORING_OP_RECV) { kmsg->msg.msg_name = NULL; kmsg->msg.msg_namelen = 0; + kmsg->msg.msg_inq = 0; kmsg->msg.msg_control = NULL; kmsg->msg.msg_get_inq = 1; kmsg->msg.msg_controllen = 0;