MIME-Version: 1.0
Date:   Fri, 07 Jan 2022 03:42:18 -0800
Message-ID: <000000000000ac7b2e05d4fc7a88@google.com>
Subject: [syzbot] KMSAN: uninit-value in from_kgid
From:   syzbot <syzbot+13e44cec8bcb2396a0a3@syzkaller.appspotmail.com>
To:     akpm@linux-foundation.org, christian.brauner@ubuntu.com,
        cxfcosmos@gmail.com, ebiederm@xmission.com, glider@google.com,
        legion@kernel.org, linux-kernel@vger.kernel.org, serge@hallyn.com,
        syzkaller-bugs@googlegroups.com
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hello,

syzbot found the following issue on:

HEAD commit:    81c325bbf94e kmsan: hooks: do not check memory in kmsan_in..
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=10071b99b00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2d8b9a11641dc9aa
dashboard link: https://syzkaller.appspot.com/bug?extid=13e44cec8bcb2396a0a3
compiler:       clang version 14.0.0 (/usr/local/google/src/llvm-git-monorepo 2b554920f11c8b763cd9ed9003f4e19b919b8e1f), GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: i386

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+13e44cec8bcb2396a0a3@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in map_id_up_base kernel/user_namespace.c:335 [inline]
BUG: KMSAN: uninit-value in map_id_up kernel/user_namespace.c:365 [inline]
BUG: KMSAN: uninit-value in from_kgid+0x52e/0xbe0 kernel/user_namespace.c:481
 map_id_up_base kernel/user_namespace.c:335 [inline]
 map_id_up kernel/user_namespace.c:365 [inline]
 from_kgid+0x52e/0xbe0 kernel/user_namespace.c:481
 p9pdu_vwritef+0x18d0/0x5100 net/9p/protocol.c:405
 p9pdu_writef+0x240/0x290 net/9p/protocol.c:539
 p9pdu_vwritef+0x21ed/0x5100 net/9p/protocol.c:490
 p9_client_prepare_req+0xe64/0x16d0 net/9p/client.c:703
 p9_client_rpc+0x28b/0x1460 net/9p/client.c:734
 p9_client_setattr+0x113/0x2c0 net/9p/client.c:1894
 v9fs_vfs_setattr_dotl+0x7e2/0xd70 fs/9p/vfs_inode_dotl.c:588
 notify_change+0x1fde/0x2180 fs/attr.c:410
 chown_common+0x832/0xc70 fs/open.c:678
 do_fchownat+0x2df/0x4e0 fs/open.c:709
 ksys_lchown include/linux/syscalls.h:1335 [inline]
 __do_sys_lchown16 kernel/uid16.c:30 [inline]
 __se_sys_lchown16 kernel/uid16.c:28 [inline]
 __ia32_sys_lchown16+0x200/0x250 kernel/uid16.c:28
 do_syscall_32_irqs_on arch/x86/entry/common.c:114 [inline]
 __do_fast_syscall_32+0x96/0xf0 arch/x86/entry/common.c:180
 do_fast_syscall_32+0x34/0x70 arch/x86/entry/common.c:205
 do_SYSENTER_32+0x1b/0x20 arch/x86/entry/common.c:248
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c

Uninit was stored to memory at:
 v9fs_vfs_setattr_dotl+0x5a9/0xd70 fs/9p/vfs_inode_dotl.c:566
 notify_change+0x1fde/0x2180 fs/attr.c:410
 chown_common+0x832/0xc70 fs/open.c:678
 do_fchownat+0x2df/0x4e0 fs/open.c:709
 ksys_lchown include/linux/syscalls.h:1335 [inline]
 __do_sys_lchown16 kernel/uid16.c:30 [inline]
 __se_sys_lchown16 kernel/uid16.c:28 [inline]
 __ia32_sys_lchown16+0x200/0x250 kernel/uid16.c:28
 do_syscall_32_irqs_on arch/x86/entry/common.c:114 [inline]
 __do_fast_syscall_32+0x96/0xf0 arch/x86/entry/common.c:180
 do_fast_syscall_32+0x34/0x70 arch/x86/entry/common.c:205
 do_SYSENTER_32+0x1b/0x20 arch/x86/entry/common.c:248
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c

Local variable newattrs created at:
 chown_common+0x120/0xc70 fs/open.c:647
 do_fchownat+0x2df/0x4e0 fs/open.c:709

CPU: 0 PID: 31712 Comm: syz-executor.3 Not tainted 5.16.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
=====================================================


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