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") Cc: stable@vger.kernel.org # v4.19+ Reviewed-by: Atish Patra atishp@rivosinc.com Signed-off-by: Andrew Bresticker abrestic@rivosinc.com --- v1 -> v2: Update access_error() to account for write-implies-read v2 -> v3: Separate into two commits --- 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 571556bb9261..5d3f2fbeb33c 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)); }