[syzbot] [block?] KMSAN: kernel-infoleak in filemap_read

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 861deac3b092 Linux 6.7-rc7
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=14d12f76e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=e0c7078a6b901aa3
dashboard link: https://syzkaller.appspot.com/bug?extid=905d785c4923bea2c1db
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=15ef73d6e80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15d27f76e80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0ea60ee8ed32/disk-861deac3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6d69fdc33021/vmlinux-861deac3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f0158750d452/bzImage-861deac3.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/52b4443ce279/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+905d78...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:114 [inline]
BUG: KMSAN: kernel-infoleak in copy_to_user_iter lib/iov_iter.c:24 [inline]
BUG: KMSAN: kernel-infoleak in iterate_ubuf include/linux/iov_iter.h:29 [inline]
BUG: KMSAN: kernel-infoleak in iterate_and_advance2 include/linux/iov_iter.h:245 [inline]
BUG: KMSAN: kernel-infoleak in iterate_and_advance include/linux/iov_iter.h:271 [inline]
BUG: KMSAN: kernel-infoleak in _copy_to_iter+0x364/0x2520 lib/iov_iter.c:186
instrument_copy_to_user include/linux/instrumented.h:114 [inline]
copy_to_user_iter lib/iov_iter.c:24 [inline]
iterate_ubuf include/linux/iov_iter.h:29 [inline]
iterate_and_advance2 include/linux/iov_iter.h:245 [inline]
iterate_and_advance include/linux/iov_iter.h:271 [inline]
_copy_to_iter+0x364/0x2520 lib/iov_iter.c:186
copy_page_to_iter+0x419/0x870 lib/iov_iter.c:381
copy_folio_to_iter include/linux/uio.h:181 [inline]
filemap_read+0xc00/0x14d0 mm/filemap.c:2644
blkdev_read_iter+0x6c0/0x8e0 block/fops.c:742
call_read_iter include/linux/fs.h:2014 [inline]
new_sync_read fs/read_write.c:389 [inline]
vfs_read+0x8f6/0xe00 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:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

Uninit was stored to memory at:
memcpy_to_iter lib/iov_iter.c:65 [inline]
iterate_bvec include/linux/iov_iter.h:122 [inline]
iterate_and_advance2 include/linux/iov_iter.h:249 [inline]
iterate_and_advance include/linux/iov_iter.h:271 [inline]
_copy_to_iter+0xe41/0x2520 lib/iov_iter.c:186
copy_page_to_iter+0x419/0x870 lib/iov_iter.c:381
shmem_file_read_iter+0xa0a/0x12b0 mm/shmem.c:2841
do_iter_read+0xd21/0x1380 fs/read_write.c:795
vfs_iter_read+0x8e/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:1915 [inline]
loop_process_work+0x12e7/0x39d0 drivers/block/loop.c:1950
loop_rootcg_workfn+0x2b/0x30 drivers/block/loop.c:1981
process_one_work kernel/workqueue.c:2627 [inline]
process_scheduled_works+0x104e/0x1e70 kernel/workqueue.c:2700
worker_thread+0xf45/0x1490 kernel/workqueue.c:2781
kthread+0x3ed/0x540 kernel/kthread.c:388
ret_from_fork+0x66/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242

Uninit was stored to memory at:
memcpy_from_iter lib/iov_iter.c:73 [inline]
iterate_bvec include/linux/iov_iter.h:122 [inline]
iterate_and_advance2 include/linux/iov_iter.h:249 [inline]
iterate_and_advance include/linux/iov_iter.h:271 [inline]
__copy_from_iter lib/iov_iter.c:268 [inline]
copy_page_from_iter_atomic+0x12f1/0x2b70 lib/iov_iter.c:500
generic_perform_write+0x4ae/0xc40 mm/filemap.c:3926
shmem_file_write_iter+0x2b5/0x2e0 mm/shmem.c:2895
do_iter_write+0xceb/0x1340 fs/read_write.c:860
vfs_iter_write+0x8e/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:1915 [inline]
loop_process_work+0x20c3/0x39d0 drivers/block/loop.c:1950
loop_rootcg_workfn+0x2b/0x30 drivers/block/loop.c:1981
process_one_work kernel/workqueue.c:2627 [inline]
process_scheduled_works+0x104e/0x1e70 kernel/workqueue.c:2700
worker_thread+0xf45/0x1490 kernel/workqueue.c:2781
kthread+0x3ed/0x540 kernel/kthread.c:388
ret_from_fork+0x66/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242

Uninit was stored to memory at:
memcpy_to_page include/linux/highmem.h:427 [inline]
hfsplus_bnode_write+0xee/0x2e0 fs/hfsplus/bnode.c:83
hfsplus_brec_insert+0xa9d/0x1400 fs/hfsplus/brec.c:133
hfsplus_create_cat+0x1309/0x1810 fs/hfsplus/catalog.c:308
hfsplus_link+0x7d8/0xbf0 fs/hfsplus/dir.c:342
vfs_link+0x936/0xb60 fs/namei.c:4588
do_linkat+0x6e1/0x1160 fs/namei.c:4659
__do_sys_link fs/namei.c:4693 [inline]
__se_sys_link fs/namei.c:4691 [inline]
__x64_sys_link+0xec/0x140 fs/namei.c:4691
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

Uninit was stored to memory at:
hfsplus_cat_build_record fs/hfsplus/catalog.c:167 [inline]
hfsplus_create_cat+0x11d1/0x1810 fs/hfsplus/catalog.c:300
hfsplus_link+0x7d8/0xbf0 fs/hfsplus/dir.c:342
vfs_link+0x936/0xb60 fs/namei.c:4588
do_linkat+0x6e1/0x1160 fs/namei.c:4659
__do_sys_link fs/namei.c:4693 [inline]
__se_sys_link fs/namei.c:4691 [inline]
__x64_sys_link+0xec/0x140 fs/namei.c:4691
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

Uninit was created at:
__alloc_pages+0x9a4/0xe00 mm/page_alloc.c:4591
alloc_pages_mpol+0x62b/0x9d0 mm/mempolicy.c:2133
alloc_pages+0x1be/0x1e0 mm/mempolicy.c:2204
alloc_slab_page mm/slub.c:1870 [inline]
allocate_slab mm/slub.c:2017 [inline]
new_slab+0x421/0x1570 mm/slub.c:2070
___slab_alloc+0x13db/0x33d0 mm/slub.c:3223
__slab_alloc mm/slub.c:3322 [inline]
__slab_alloc_node mm/slub.c:3375 [inline]
slab_alloc_node mm/slub.c:3468 [inline]
slab_alloc mm/slub.c:3486 [inline]
__kmem_cache_alloc_lru mm/slub.c:3493 [inline]
kmem_cache_alloc_lru+0x552/0x970 mm/slub.c:3509
alloc_inode_sb include/linux/fs.h:2937 [inline]
hfsplus_alloc_inode+0x5a/0xc0 fs/hfsplus/super.c:627
alloc_inode+0x83/0x440 fs/inode.c:261
iget_locked+0x2dd/0xe80 fs/inode.c:1316
hfsplus_iget+0x59/0xaf0 fs/hfsplus/super.c:64
hfsplus_btree_open+0x13e/0x1d00 fs/hfsplus/btree.c:150
hfsplus_fill_super+0x1113/0x26f0 fs/hfsplus/super.c:473
mount_bdev+0x3d7/0x560 fs/super.c:1650
hfsplus_mount+0x4d/0x60 fs/hfsplus/super.c:641
legacy_get_tree+0x110/0x290 fs/fs_context.c:662
vfs_get_tree+0xa5/0x520 fs/super.c:1771
do_new_mount+0x68d/0x1550 fs/namespace.c:3337
path_mount+0x73d/0x1f20 fs/namespace.c:3664
do_mount fs/namespace.c:3677 [inline]
__do_sys_mount fs/namespace.c:3886 [inline]
__se_sys_mount+0x725/0x810 fs/namespace.c:3863
__x64_sys_mount+0xe4/0x140 fs/namespace.c:3863
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

Bytes 3258-3261 of 4096 are uninitialized
Memory access of size 4096 starts at ffff8881146b8000
Data copied to user address 000055ff3929d058

CPU: 1 PID: 5003 Comm: udevd Not tainted 6.7.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
=====================================================


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