From: Russell Currey ruscur@russell.cc
[ 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 | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index 2bef19cc1b98c..af46aa88422bf 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c @@ -271,11 +271,16 @@ static bool access_error(bool is_write, bool is_exec, struct vm_area_struct *vma }
/* - * Check for a read fault. This could be caused by a read on an - * inaccessible page (i.e. PROT_NONE), or a Radix MMU execute-only page. + * VM_READ, VM_WRITE and VM_EXEC all imply read permissions, as + * defined in protection_map[]. Read faults can only be caused by + * a PROT_NONE mapping, or with a PROT_EXEC-only mapping on Radix. */ - if (unlikely(!(vma->vm_flags & VM_READ))) + if (unlikely(!vma_is_accessible(vma))) return true; + + if (unlikely(radix_enabled() && ((vma->vm_flags & VM_ACCESS_FLAGS) == VM_EXEC))) + return true; + /* * We should ideally do the vma pkey access check here. But in the * fault path, handle_mm_fault() also does the same check. To avoid