arm64: mm: Fix VM_BUG_ON(mm != &init_mm) for trans_pgd

trans_pgd_create_copy() can hit "VM_BUG_ON(mm != &init_mm)" in the
function pmd_populate_kernel().

This is the combined consequence of commit 5de59884ac0e ("arm64:
trans_pgd: pass NULL instead of init_mm to *_populate functions"), which
replaced &init_mm with NULL and commit 59511cfd08f3 ("arm64: mm: use XN
table mapping attributes for user/kernel mappings"), which introduced
the VM_BUG_ON.

Since the former sounds reasonable, it is better to work on the later.
From the perspective of trans_pgd, two groups of functions are
considered in the later one:

  pmd_populate_kernel()
    mm == NULL should be fixed, else it hits VM_BUG_ON()
  p?d_populate()
    mm == NULL means PXN, that is OK, since trans_pgd only copies a
    linear map, no execution will happen on the map.

So it is good enough to just relax VM_BUG_ON() to disregard mm == NULL

Fixes: 59511cfd08f3 ("arm64: mm: use XN table mapping attributes for user/kernel mappings")
Signed-off-by: Pingfan Liu <[email protected]>
Cc: <[email protected]> # 5.13.x
Cc: Ard Biesheuvel <[email protected]>
Cc: James Morse <[email protected]>
Cc: Matthias Brugger <[email protected]>
Reviewed-by: Catalin Marinas <[email protected]>
Reviewed-by: Pasha Tatashin <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

0 files changed, 0 insertions, 0 deletions