io_uring/sqpoll: retain test for whether the CPU is valid

commit a09c17240bdf2e9fa6d0591afa9448b59785f7d4 upstream.

A recent commit ensured that SQPOLL cannot be setup with a CPU that
isn't in the current tasks cpuset, but it also dropped testing whether
the CPU is valid in the first place. Without that, if a task passes in
a CPU value that is too high, the following KASAN splat can get
triggered:

BUG: KASAN: stack-out-of-bounds in io_sq_offload_create+0x858/0xaa4
Read of size 8 at addr ffff800089bc7b90 by task wq-aff.t/1391

CPU: 4 UID: 1000 PID: 1391 Comm: wq-aff.t Not tainted 6.11.0-rc7-00227-g371c468f4db6 #7080
Hardware name: linux,dummy-virt (DT)
Call trace:
 dump_backtrace.part.0+0xcc/0xe0
 show_stack+0x14/0x1c
 dump_stack_lvl+0x58/0x74
 print_report+0x16c/0x4c8
 kasan_report+0x9c/0xe4
 __asan_report_load8_noabort+0x1c/0x24
 io_sq_offload_create+0x858/0xaa4
 io_uring_setup+0x1394/0x17c4
 __arm64_sys_io_uring_setup+0x6c/0x180
 invoke_syscall+0x6c/0x260
 el0_svc_common.constprop.0+0x158/0x224
 do_el0_svc+0x3c/0x5c
 el0_svc+0x34/0x70
 el0t_64_sync_handler+0x118/0x124
 el0t_64_sync+0x168/0x16c

The buggy address belongs to stack of task wq-aff.t/1391
 and is located at offset 48 in frame:
 io_sq_offload_create+0x0/0xaa4

This frame has 1 object:
 [32, 40) 'allowed_mask'

The buggy address belongs to the virtual mapping at
 [ffff800089bc0000, ffff800089bc9000) created by:
 kernel_clone+0x124/0x7e0

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff0000d740af80 pfn:0x11740a
memcg:ffff0000c2706f02
flags: 0xbffe00000000000(node=0|zone=2|lastcpupid=0x1fff)
raw: 0bffe00000000000 0000000000000000 dead000000000122 0000000000000000
raw: ffff0000d740af80 0000000000000000 00000001ffffffff ffff0000c2706f02
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff800089bc7a80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff800089bc7b00: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1
>ffff800089bc7b80: 00 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
                         ^
 ffff800089bc7c00: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1
 ffff800089bc7c80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f3

Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202409161632.cbeeca0d-lkp@intel.com
Fixes: f011c9cf04c0 ("io_uring/sqpoll: do not allow pinning outside of cpuset")
Tested-by: Felix Moessbauer <felix.moessbauer@siemens.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Felix Moessbauer <felix.moessbauer@siemens.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 6b6fd244233f..a260852a0490 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -8751,6 +8751,8 @@ static int io_sq_offload_create(struct io_ring_ctx *ctx,
 			int cpu = p->sq_thread_cpu;
 
 			ret = -EINVAL;
+			if (cpu >= nr_cpu_ids || !cpu_online(cpu))
+				goto err_sqpoll;
 			cpuset_cpus_allowed(current, &allowed_mask);
 			if (!cpumask_test_cpu(cpu, &allowed_mask))
 				goto err_sqpoll;