[syzbot] [block?] KMSAN: kernel-infoleak in copy_page_to_iter (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    7cccf3be6dcb string: use __builtin_memcpy() in strlcpy/str..
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=1228ed9b280000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5e9e8900159378
dashboard link: https://syzkaller.appspot.com/bug?extid=17a061f6132066e9fb95
compiler:       Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: i386

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5e08b958e39c/disk-7cccf3be.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9003cbdf6555/vmlinux-7cccf3be.xz
kernel image: https://storage.googleapis.com/syzbot-assets/192dba10f451/bzImage-7cccf3be.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+17a061f6132066e9fb95@xxxxxxxxxxxxxxxxxxxxxxxxx

=====================================================
BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:114 [inline]
BUG: KMSAN: kernel-infoleak in copyout lib/iov_iter.c:169 [inline]
BUG: KMSAN: kernel-infoleak in _copy_to_iter+0x420/0x1d00 lib/iov_iter.c:536
 instrument_copy_to_user include/linux/instrumented.h:114 [inline]
 copyout lib/iov_iter.c:169 [inline]
 _copy_to_iter+0x420/0x1d00 lib/iov_iter.c:536
 copy_page_to_iter+0x46e/0x920 lib/iov_iter.c:742
 copy_folio_to_iter include/linux/uio.h:197 [inline]
 filemap_read+0xc37/0x14f0 mm/filemap.c:2742
 blkdev_read_iter+0xa1b/0xbc0 block/fops.c:606
 call_read_iter include/linux/fs.h:1862 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x933/0xe40 fs/read_write.c:470
 ksys_read+0x20f/0x4c0 fs/read_write.c:613
 __do_sys_read fs/read_write.c:623 [inline]
 __se_sys_read fs/read_write.c:621 [inline]
 __x64_sys_read+0x93/0xd0 fs/read_write.c:621
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Uninit was stored to memory at:
 _copy_to_iter+0xc9e/0x1d00 lib/iov_iter.c:536
 copy_page_to_iter+0x46e/0x920 lib/iov_iter.c:742
 shmem_file_read_iter+0xac2/0x1310 mm/shmem.c:2696
 do_iter_read+0xd0a/0x1340 fs/read_write.c:795
 vfs_iter_read+0x88/0xe0 fs/read_write.c:837
 lo_read_simple drivers/block/loop.c:290 [inline]
 do_req_filebacked drivers/block/loop.c:500 [inline]
 loop_handle_cmd drivers/block/loop.c:1888 [inline]
 loop_process_work+0x12c9/0x3990 drivers/block/loop.c:1923
 loop_rootcg_workfn+0x2b/0x30 drivers/block/loop.c:1954
 process_one_work+0xb0d/0x1410 kernel/workqueue.c:2405
 worker_thread+0x107e/0x1d60 kernel/workqueue.c:2552
 kthread+0x3e8/0x540 kernel/kthread.c:379
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

Uninit was stored to memory at:
 memcpy_from_iter lib/iov_iter.c:639 [inline]
 copy_page_from_iter_atomic+0x1271/0x26d0 lib/iov_iter.c:872
 generic_perform_write+0x4a2/0xbb0 mm/filemap.c:3931
 __generic_file_write_iter+0x393/0x920 mm/filemap.c:4051
 generic_file_write_iter+0x103/0x5b0 mm/filemap.c:4083
 do_iter_write+0x605/0x1310 fs/read_write.c:860
 vfs_iter_write+0x88/0xe0 fs/read_write.c:901
 lo_write_bvec drivers/block/loop.c:249 [inline]
 lo_write_simple drivers/block/loop.c:271 [inline]
 do_req_filebacked drivers/block/loop.c:495 [inline]
 loop_handle_cmd drivers/block/loop.c:1888 [inline]
 loop_process_work+0x206d/0x3990 drivers/block/loop.c:1923
 loop_workfn+0x48/0x60 drivers/block/loop.c:1947
 process_one_work+0xb0d/0x1410 kernel/workqueue.c:2405
 worker_thread+0x107e/0x1d60 kernel/workqueue.c:2552
 kthread+0x3e8/0x540 kernel/kthread.c:379
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

Uninit was stored to memory at:
 copy_to_dinode+0x88d/0xb40 fs/jfs/jfs_imap.c:3148
 diWrite+0x1bf0/0x1f00 fs/jfs/jfs_imap.c:786
 txCommit+0xe52/0x8f40 fs/jfs/jfs_txnmgr.c:1250
 __jfs_xattr_set+0x1b3/0x1f0 fs/jfs/xattr.c:919
 jfs_xattr_set+0x79/0x90 fs/jfs/xattr.c:941
 __vfs_setxattr+0x7aa/0x8b0 fs/xattr.c:201
 __vfs_setxattr_noperm+0x24f/0xa30 fs/xattr.c:235
 __vfs_setxattr_locked+0x441/0x480 fs/xattr.c:296
 vfs_setxattr+0x294/0x650 fs/xattr.c:322
 do_setxattr fs/xattr.c:630 [inline]
 setxattr+0x45f/0x540 fs/xattr.c:653
 __do_sys_fsetxattr fs/xattr.c:709 [inline]
 __se_sys_fsetxattr+0x2bb/0x420 fs/xattr.c:698
 __ia32_sys_fsetxattr+0xe3/0x150 fs/xattr.c:698
 do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
 __do_fast_syscall_32+0xa2/0x100 arch/x86/entry/common.c:178
 do_fast_syscall_32+0x37/0x80 arch/x86/entry/common.c:203
 do_SYSENTER_32+0x1f/0x30 arch/x86/entry/common.c:246
 entry_SYSENTER_compat_after_hwframe+0x70/0x82

Uninit was stored to memory at:
 ea_put fs/jfs/xattr.c:637 [inline]
 __jfs_setxattr+0x1877/0x1b90 fs/jfs/xattr.c:783
 __jfs_xattr_set+0xe6/0x1f0 fs/jfs/xattr.c:917
 jfs_xattr_set+0x79/0x90 fs/jfs/xattr.c:941
 __vfs_setxattr+0x7aa/0x8b0 fs/xattr.c:201
 __vfs_setxattr_noperm+0x24f/0xa30 fs/xattr.c:235
 __vfs_setxattr_locked+0x441/0x480 fs/xattr.c:296
 vfs_setxattr+0x294/0x650 fs/xattr.c:322
 do_setxattr fs/xattr.c:630 [inline]
 setxattr+0x45f/0x540 fs/xattr.c:653
 __do_sys_fsetxattr fs/xattr.c:709 [inline]
 __se_sys_fsetxattr+0x2bb/0x420 fs/xattr.c:698
 __ia32_sys_fsetxattr+0xe3/0x150 fs/xattr.c:698
 do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
 __do_fast_syscall_32+0xa2/0x100 arch/x86/entry/common.c:178
 do_fast_syscall_32+0x37/0x80 arch/x86/entry/common.c:203
 do_SYSENTER_32+0x1f/0x30 arch/x86/entry/common.c:246
 entry_SYSENTER_compat_after_hwframe+0x70/0x82

Local variable ea_buf created at:
 __jfs_setxattr+0x5d/0x1b90 fs/jfs/xattr.c:660
 __jfs_xattr_set+0xe6/0x1f0 fs/jfs/xattr.c:917

Bytes 3689-3691 of 4096 are uninitialized
Memory access of size 4096 starts at ffff88815f2ee000
Data copied to user address 000055a672e8dc78

CPU: 1 PID: 7649 Comm: udevd Not tainted 6.4.0-rc6-syzkaller-g7cccf3be6dcb #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
=====================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the bug is already fixed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to change bug's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the bug is a duplicate of another bug, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup