powerpc/mm: Fix false detection of read faults
authorRussell Currey <ruscur@russell.cc>
Fri, 10 Mar 2023 05:08:34 +0000 (16:08 +1100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 22 Mar 2023 12:33:47 +0000 (13:33 +0100)
commit5ca66a9fff75a1468fa6160761ccb95832cbbe16
tree82cc98a47c954117292e445cc44b44e15778dda8
parent9821576e117047e4bf8e92a673272aa014a3bb2e
powerpc/mm: Fix false detection of read faults

[ Upstream commit f2c7e3562b4c4f1699acc1538ebf3e75f5cced35 ]

To support detection of read faults with Radix execute-only memory, the
vma_is_accessible() check in access_error() (which checks for PROT_NONE)
was replaced with a check to see if VM_READ was missing, and if so,
returns true to assert the fault was caused by a bad read.

This is incorrect, as it ignores that both VM_WRITE and VM_EXEC imply
read on powerpc, as defined in protection_map[].  This causes mappings
containing VM_WRITE or VM_EXEC without VM_READ to misreport the cause of
page faults, since the MMU is still allowing reads.

Correct this by restoring the original vma_is_accessible() check for
PROT_NONE mappings, and adding a separate check for Radix PROT_EXEC-only
mappings.

Fixes: 395cac7752b9 ("powerpc/mm: Support execute-only memory on the Radix MMU")
Reported-by: Michal Suchánek <msuchanek@suse.de>
Link: https://lore.kernel.org/r/20230308152702.GR19419@kitsune.suse.cz
Tested-by: Benjamin Gray <bgray@linux.ibm.com>
Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230310050834.63105-1-ruscur@russell.cc
Signed-off-by: Sasha Levin <sashal@kernel.org>
arch/powerpc/mm/fault.c