From 7ab72c597356be1e7f0f3d856e54ce78527f43c8 Mon Sep 17 00:00:00 2001 From: Andrew Bresticker Date: Thu, 15 Sep 2022 15:37:01 -0400 Subject: [PATCH 1/2] riscv: Make VM_WRITE imply VM_READ RISC-V does not presently have write-only mappings as that PTE bit pattern is considered reserved in the privileged spec, so allow handling of read faults in VMAs that have VM_WRITE without VM_READ in order to be consistent with other architectures that have similar limitations. Fixes: 2139619bcad7 ("riscv: mmap with PROT_WRITE but no PROT_READ is invalid") Reviewed-by: Atish Patra Signed-off-by: Andrew Bresticker Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20220915193702.2201018-2-abrestic@rivosinc.com/ Signed-off-by: Palmer Dabbelt --- arch/riscv/mm/fault.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c index f2fbd1400b7c9..d86f7cebd4a7e 100644 --- a/arch/riscv/mm/fault.c +++ b/arch/riscv/mm/fault.c @@ -184,7 +184,8 @@ static inline bool access_error(unsigned long cause, struct vm_area_struct *vma) } break; case EXC_LOAD_PAGE_FAULT: - if (!(vma->vm_flags & VM_READ)) { + /* Write implies read */ + if (!(vma->vm_flags & (VM_READ | VM_WRITE))) { return true; } break; From 9e2e6042a7ec6504fe8e366717afa2f40cf16488 Mon Sep 17 00:00:00 2001 From: Andrew Bresticker Date: Thu, 15 Sep 2022 15:37:02 -0400 Subject: [PATCH 2/2] riscv: Allow PROT_WRITE-only mmap() Commit 2139619bcad7 ("riscv: mmap with PROT_WRITE but no PROT_READ is invalid") made mmap() return EINVAL if PROT_WRITE was set wihtout PROT_READ with the justification that a write-only PTE is considered a reserved PTE permission bit pattern in the privileged spec. This check is unnecessary since we let VM_WRITE imply VM_READ on RISC-V, and it is inconsistent with other architectures that don't support write-only PTEs, creating a potential software portability issue. Just remove the check altogether and let PROT_WRITE imply PROT_READ as is the case on other architectures. Note that this also allows PROT_WRITE|PROT_EXEC mappings which were disallowed prior to the aforementioned commit; PROT_READ is implied in such mappings as well. Fixes: 2139619bcad7 ("riscv: mmap with PROT_WRITE but no PROT_READ is invalid") Reviewed-by: Atish Patra Signed-off-by: Andrew Bresticker Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20220915193702.2201018-3-abrestic@rivosinc.com/ Signed-off-by: Palmer Dabbelt --- arch/riscv/kernel/sys_riscv.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c index 571556bb9261a..5d3f2fbeb33c7 100644 --- a/arch/riscv/kernel/sys_riscv.c +++ b/arch/riscv/kernel/sys_riscv.c @@ -18,9 +18,6 @@ static long riscv_sys_mmap(unsigned long addr, unsigned long len, if (unlikely(offset & (~PAGE_MASK >> page_shift_offset))) return -EINVAL; - if (unlikely((prot & PROT_WRITE) && !(prot & PROT_READ))) - return -EINVAL; - return ksys_mmap_pgoff(addr, len, prot, flags, fd, offset >> (PAGE_SHIFT - page_shift_offset)); }