arm[64]/memremap: don't abuse pfn_valid() to ensure presence of linear map

The semantics of pfn_valid() is to check presence of the memory map for a
PFN and not whether a PFN is covered by the linear map.  The memory map
may be present for NOMAP memory regions, but they won't be mapped in the
linear mapping.  Accessing such regions via __va() when they are
memremap()'ed will cause a crash.

On v5.4.y the crash happens on qemu-arm with UEFI [1]:

<1>[    0.084476] 8<--- cut here ---
<1>[    0.084595] Unable to handle kernel paging request at virtual address dfb76000
<1>[    0.084938] pgd = (ptrval)
<1>[    0.085038] [dfb76000] *pgd=5f7fe801, *pte=00000000, *ppte=00000000

...

<4>[    0.093923] [<c0ed6ce8>] (memcpy) from [<c16a06f8>] (dmi_setup+0x60/0x418)
<4>[    0.094204] [<c16a06f8>] (dmi_setup) from [<c16a38d4>] (arm_dmi_init+0x8/0x10)
<4>[    0.094408] [<c16a38d4>] (arm_dmi_init) from [<c0302e9c>] (do_one_initcall+0x50/0x228)
<4>[    0.094619] [<c0302e9c>] (do_one_initcall) from [<c16011e4>] (kernel_init_freeable+0x15c/0x1f8)
<4>[    0.094841] [<c16011e4>] (kernel_init_freeable) from [<c0f028cc>] (kernel_init+0x8/0x10c)
<4>[    0.095057] [<c0f028cc>] (kernel_init) from [<c03010e8>] (ret_from_fork+0x14/0x2c)

On kernels v5.10.y and newer the same crash won't reproduce on ARM because
commit b10d6bca8720 ("arch, drivers: replace for_each_membock() with
for_each_mem_range()") changed the way memory regions are registered in
the resource tree, but that merely covers up the problem.

On ARM64 memory resources registered in yet another way and there the
issue of wrong usage of pfn_valid() to ensure availability of the linear
map is also covered.

Implement arch_memremap_can_ram_remap() on ARM and ARM64 to prevent access
to NOMAP regions via the linear mapping in memremap().

Link: https://lore.kernel.org/all/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Mike Rapoport <[email protected]>
Reported-by: "kernelci.org bot" <[email protected]>
Tested-by: Mark Brown <[email protected]>
Reviewed-by: Ard Biesheuvel <[email protected]>
Acked-by: Catalin Marinas <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Mark Brown <[email protected]>
Cc: Mark-PK Tsai <[email protected]>
Cc: Russell King <[email protected]>
Cc: Tony Lindgren <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: <[email protected]>	[5.4+]
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions