[syzbot] [exfat?] KMSAN: uninit-value in exfat_iterate

[syzbot <syzbot+84345a1b4057358168d9@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    3022e9d00ebe Merge tag 'sched_ext-for-6.12-rc7-fixes' of g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=177941a7980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=dcca673786a14715
dashboard link: https://syzkaller.appspot.com/bug?extid=84345a1b4057358168d9
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: i386

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/937339c4ba17/disk-3022e9d0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/23acd73c301b/vmlinux-3022e9d0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/66d14471611f/bzImage-3022e9d0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+84345a1b4057358168d9@syzkaller.appspotmail.com

exFAT-fs (loop1): failed to load upcase table (idx : 0x0001e4a3, chksum : 0x009ea0b8, utbl_chksum : 0x7319d30d)
=====================================================
BUG: KMSAN: uninit-value in exfat_get_entry_type fs/exfat/dir.c:348 [inline]
BUG: KMSAN: uninit-value in exfat_readdir fs/exfat/dir.c:125 [inline]
BUG: KMSAN: uninit-value in exfat_iterate+0x1346/0x3f90 fs/exfat/dir.c:261
 exfat_get_entry_type fs/exfat/dir.c:348 [inline]
 exfat_readdir fs/exfat/dir.c:125 [inline]
 exfat_iterate+0x1346/0x3f90 fs/exfat/dir.c:261
 wrap_directory_iterator+0xf3/0x190 fs/readdir.c:65
 shared_exfat_iterate+0x3c/0x50 fs/exfat/dir.c:309
 iterate_dir+0x5b3/0x9e0 fs/readdir.c:108
 __do_compat_sys_getdents fs/readdir.c:575 [inline]
 __se_compat_sys_getdents+0x171/0x550 fs/readdir.c:560
 __ia32_compat_sys_getdents+0x93/0xe0 fs/readdir.c:560
 ia32_sys_call+0x12f8/0x40d0 arch/x86/include/generated/asm/syscalls_32.h:142
 do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
 __do_fast_syscall_32+0xb0/0x110 arch/x86/entry/common.c:386
 do_fast_syscall_32+0x38/0x80 arch/x86/entry/common.c:411
 do_SYSENTER_32+0x1f/0x30 arch/x86/entry/common.c:449
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

Uninit was stored to memory at:
 memcpy_to_iter lib/iov_iter.c:65 [inline]
 iterate_bvec include/linux/iov_iter.h:123 [inline]
 iterate_and_advance2 include/linux/iov_iter.h:304 [inline]
 iterate_and_advance include/linux/iov_iter.h:328 [inline]
 _copy_to_iter+0xe5a/0x2b30 lib/iov_iter.c:185
 copy_page_to_iter+0x419/0x880 lib/iov_iter.c:362
 shmem_file_read_iter+0xa09/0x12b0 mm/shmem.c:3161
 do_iter_readv_writev+0x88a/0xa30
 vfs_iter_read+0x278/0x760 fs/read_write.c:923
 lo_read_simple drivers/block/loop.c:283 [inline]
 do_req_filebacked drivers/block/loop.c:516 [inline]
 loop_handle_cmd drivers/block/loop.c:1910 [inline]
 loop_process_work+0x20fc/0x3750 drivers/block/loop.c:1945
 loop_workfn+0x48/0x60 drivers/block/loop.c:1969
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0xae0/0x1c40 kernel/workqueue.c:3310
 worker_thread+0xea7/0x14f0 kernel/workqueue.c:3391
 kthread+0x3e2/0x540 kernel/kthread.c:389
 ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Uninit was stored to memory at:
 memcpy_from_iter lib/iov_iter.c:73 [inline]
 iterate_bvec include/linux/iov_iter.h:123 [inline]
 iterate_and_advance2 include/linux/iov_iter.h:304 [inline]
 iterate_and_advance include/linux/iov_iter.h:328 [inline]
 __copy_from_iter lib/iov_iter.c:249 [inline]
 copy_page_from_iter_atomic+0x1299/0x30c0 lib/iov_iter.c:483
 copy_folio_from_iter_atomic include/linux/uio.h:201 [inline]
 generic_perform_write+0x8d1/0x1080 mm/filemap.c:4066
 shmem_file_write_iter+0x2ba/0x2f0 mm/shmem.c:3215
 do_iter_readv_writev+0x88a/0xa30
 vfs_iter_write+0x44d/0xd40 fs/read_write.c:988
 lo_write_bvec drivers/block/loop.c:243 [inline]
 lo_write_simple drivers/block/loop.c:264 [inline]
 do_req_filebacked drivers/block/loop.c:511 [inline]
 loop_handle_cmd drivers/block/loop.c:1910 [inline]
 loop_process_work+0x15e6/0x3750 drivers/block/loop.c:1945
 loop_workfn+0x48/0x60 drivers/block/loop.c:1969
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0xae0/0x1c40 kernel/workqueue.c:3310
 worker_thread+0xea7/0x14f0 kernel/workqueue.c:3391
 kthread+0x3e2/0x540 kernel/kthread.c:389
 ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Uninit was created at:
 __alloc_pages_noprof+0x9a7/0xe00 mm/page_alloc.c:4758
 alloc_pages_mpol_noprof+0x299/0x990 mm/mempolicy.c:2265
 alloc_pages_noprof mm/mempolicy.c:2345 [inline]
 folio_alloc_noprof+0x1db/0x310 mm/mempolicy.c:2352
 filemap_alloc_folio_noprof+0xa6/0x440 mm/filemap.c:1010
 __filemap_get_folio+0xac4/0x1550 mm/filemap.c:1952
 block_write_begin+0x6e/0x2b0 fs/buffer.c:2226
 exfat_write_begin+0xfb/0x400 fs/exfat/inode.c:434
 exfat_extend_valid_size fs/exfat/file.c:553 [inline]
 exfat_file_write_iter+0x474/0xfb0 fs/exfat/file.c:588
 do_iter_readv_writev+0x88a/0xa30
 vfs_writev+0x56a/0x14f0 fs/read_write.c:1064
 do_pwritev fs/read_write.c:1165 [inline]
 __do_compat_sys_pwritev2 fs/read_write.c:1311 [inline]
 __se_compat_sys_pwritev2+0x2a8/0x490 fs/read_write.c:1303
 __ia32_compat_sys_pwritev2+0x11d/0x1a0 fs/read_write.c:1303
 ia32_sys_call+0x2f06/0x40d0 arch/x86/include/generated/asm/syscalls_32.h:380
 do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
 __do_fast_syscall_32+0xb0/0x110 arch/x86/entry/common.c:386
 do_fast_syscall_32+0x38/0x80 arch/x86/entry/common.c:411
 do_SYSENTER_32+0x1f/0x30 arch/x86/entry/common.c:449
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

CPU: 1 UID: 0 PID: 6646 Comm: syz.1.260 Not tainted 6.12.0-rc7-syzkaller-00012-g3022e9d00ebe #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
=====================================================


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