[syzbot] [mm?] [bcachefs?] UBSAN: shift-out-of-bounds in filemap_get_entry

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    69e858e0b8b2 Merge tag 'uml-for-linus-6.14-rc1' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17814b24580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d033b14aeef39158
dashboard link: https://syzkaller.appspot.com/bug?extid=a0ae55e3dde11d2d790c
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=13877b64580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16063ddf980000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7feb34a89c2a/non_bootable_disk-69e858e0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a53b888c1f3f/vmlinux-69e858e0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6b5e17edafc0/bzImage-69e858e0.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/680b2fde83a8/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a0ae55e3dde11d2d790c@xxxxxxxxxxxxxxxxxxxxxxxxx

------------[ cut here ]------------
UBSAN: shift-out-of-bounds in lib/xarray.c:147:16
shift exponent 192 is too large for 64-bit type 'unsigned long'
CPU: 0 UID: 0 PID: 2666 Comm: kworker/u4:9 Not tainted 6.13.0-syzkaller-09760-g69e858e0b8b2 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: loop0 loop_rootcg_workfn
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 ubsan_epilogue lib/ubsan.c:231 [inline]
 __ubsan_handle_shift_out_of_bounds+0x3c8/0x420 lib/ubsan.c:468
 get_offset lib/xarray.c:147 [inline]
 xas_descend lib/xarray.c:207 [inline]
 xas_load+0x583/0x5c0 lib/xarray.c:246
 filemap_get_entry+0x1f0/0x3b0 mm/filemap.c:1860
 shmem_get_folio_gfp+0x285/0x1840 mm/shmem.c:2446
 shmem_get_folio mm/shmem.c:2628 [inline]
 shmem_write_begin+0x165/0x350 mm/shmem.c:3278
 generic_perform_write+0x346/0x990 mm/filemap.c:4189
 shmem_file_write_iter+0xf9/0x120 mm/shmem.c:3454
 do_iter_readv_writev+0x71a/0x9d0
 vfs_iter_write+0x23e/0x600 fs/read_write.c:974
 lo_write_bvec drivers/block/loop.c:245 [inline]
 lo_write_simple drivers/block/loop.c:266 [inline]
 do_req_filebacked drivers/block/loop.c:520 [inline]
 loop_handle_cmd drivers/block/loop.c:1926 [inline]
 loop_process_work+0x1429/0x21c0 drivers/block/loop.c:1961
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3317
 worker_thread+0x870/0xd30 kernel/workqueue.c:3398
 kthread+0x7a9/0x920 kernel/kthread.c:464
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>


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