[syzbot] [io-uring?] KMSAN: uninit-value in io_recv

[syzbot] [io-uring?] KMSAN: uninit-value in io_recv

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    8379578b11d5 Merge tag 'for-v6.13-rc' of git://git.kernel...
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1713fadf980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f9048090d7bb0d06
dashboard link: https://syzkaller.appspot.com/bug?extid=068ff190354d2f74892f
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1360d2c4580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11278818580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/fbfb6bbe8da9/disk-8379578b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d0d8a8059222/vmlinux-8379578b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a102540c5698/bzImage-8379578b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+068ff190354d2f74892f@syzkaller.appspotmail.com

=====================================================
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

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4125 [inline]
 slab_alloc_node mm/slub.c:4168 [inline]
 __do_kmalloc_node mm/slub.c:4297 [inline]
 __kmalloc_noprof+0x923/0x1230 mm/slub.c:4310
 kmalloc_noprof include/linux/slab.h:905 [inline]
 io_alloc_async_data+0xc0/0x220 io_uring/io_uring.c:1651
 io_msg_alloc_async io_uring/net.c:175 [inline]
 io_recvmsg_prep_setup io_uring/net.c:750 [inline]
 io_recvmsg_prep+0xbe8/0x1a20 io_uring/net.c:831
 io_init_req io_uring/io_uring.c:2120 [inline]
 io_submit_sqe io_uring/io_uring.c:2167 [inline]
 io_submit_sqes+0x1082/0x2f80 io_uring/io_uring.c:2322
 __do_sys_io_uring_enter io_uring/io_uring.c:3395 [inline]
 __se_sys_io_uring_enter+0x409/0x4ce0 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

CPU: 1 UID: 0 PID: 5781 Comm: syz-executor452 Not tainted 6.13.0-rc4-syzkaller-00069-g8379578b11d5 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
=====================================================


---
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Re: [syzbot] [io-uring?] KMSAN: uninit-value in io_recv

[Jens Axboe]

On 1/2/25 1:59 PM, syzbot wrote:

#syz test: git://git.kernel.dk/linux io_uring-6.13

-- 
Jens Axboe

Re: [syzbot] [io-uring?] KMSAN: uninit-value in io_recv

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+068ff190354d2f74892f@syzkaller.appspotmail.com
Tested-by: syzbot+068ff190354d2f74892f@syzkaller.appspotmail.com

Tested on:

commit:         c6e60a0a io_uring/net: always initialize kmsg->msg.msg..
git tree:       git://git.kernel.dk/linux io_uring-6.13
console output: https://syzkaller.appspot.com/x/log.txt?x=12de98b0580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=96ee18b6611821ab
dashboard link: https://syzkaller.appspot.com/bug?extid=068ff190354d2f74892f
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.