Messages in this thread | | | Date | Thu, 13 Oct 2022 14:01:23 -0700 (PDT) | Subject | Re: [PATCH v4 0/2] Make mmap() with PROT_WRITE imply PROT_READ | From | Palmer Dabbelt <> |
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On Thu, 15 Sep 2022 12:37:00 PDT (-0700), abrestic@rivosinc.com wrote: > Commit 2139619bcad7 ("riscv: mmap with PROT_WRITE but no PROT_READ is > invalid") made mmap() reject mappings with only PROT_WRITE set in an > attempt to fix an observed inconsistency in behavior when attempting > to read from a PROT_WRITE-only mapping. The root cause of this behavior > was actually that while RISC-V's protection_map maps VM_WRITE to > readable PTE permissions (since write-only PTEs are considered reserved > by the privileged spec), the page fault handler considered loads from > VM_WRITE-only VMAs illegal accesses. Fix the underlying cause by > handling faults in VM_WRITE-only VMAs (patch 1) and then re-enable > use of mmap(PROT_WRITE) (patch 2), making RISC-V's behavior consistent > with all other architectures that don't support write-only PTEs. > > Both patches are tagged as fixes for the aforementioned commit since that > commit made a userspace visible change that will break any software relying > on mmap(PROT_WRITE). (Also cc: stable since the offending commit was > itself backported to stable). > > v1 -> v2: Allow handling of load faults in VM_WRITE VMAs > v2 -> v3: Split into two pathces > v3 -> v4: Fixes tags (+ this cover letter) > > Andrew Bresticker (2): > riscv: Make VM_WRITE imply VM_READ > riscv: Allow PROT_WRITE-only mmap() > > arch/riscv/kernel/sys_riscv.c | 3 --- > arch/riscv/mm/fault.c | 3 ++- > 2 files changed, 2 insertions(+), 4 deletions(-)
Thanks, these are on for-next.
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