ntfs: fix kmap_local leak in ntfs_check_logfile()

ntfs_check_logfile() calls kmap_local_folio() on every iteration of its
search loop but kunmap_local() only once per folio. The loop visits
positions 0, 512, 1024, 2048, 4096 and so on. With 4 KiB pages the first
four are in one page, so a mount whose first LogFile folio is in highmem
leaves three entries on the kmap_local stack of the mounting task.
Kernels without HIGHMEM are not affected.

The leaked entries keep migration disabled. nr_pinned of the runqueue
the mount ran on stays raised after the task exits, so taking that CPU
offline blocks forever in balance_hotplug_wait().

The fifth mount in one task reaches KM_MAX_IDX (12 leaked entries plus
4 in the loop) and hits the BUG_ON() in kmap_local_idx_push():

  kernel BUG at mm/highmem.c:480!

On x86-32 the generic entry code also warns on return to user space:

  DEBUG_LOCKS_WARN_ON(current->kmap_ctrl.idx)
  WARNING: include/linux/highmem-internal.h:17 at __do_fast_syscall_32+0x21e/0x550

Map each page once, when it is read, and unmap that address.

Fixes: 5218cd102aec ("ntfs: update misc operations")
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
Reviewed-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

0 files changed, 0 insertions, 0 deletions