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authorPalmer Dabbelt <palmer@rivosinc.com>2022-10-13 22:49:12 +0300
committerPalmer Dabbelt <palmer@rivosinc.com>2022-10-13 22:49:12 +0300
commit8aeb7b17f04ef40f620c763502e2b644c5c73efd (patch)
tree41138155d3670d302192e9d8b3cf3f4aeeecac14 /arch/riscv
parentc45fc916c2b2cc2a0587659c18d6ceef9b7299be (diff)
parent9e2e6042a7ec6504fe8e366717afa2f40cf16488 (diff)
downloadlinux-8aeb7b17f04ef40f620c763502e2b644c5c73efd.tar.xz
RISC-V: Make mmap() with PROT_WRITE imply PROT_READ
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. * remotes/palmer/riscv-wonly: riscv: Allow PROT_WRITE-only mmap() riscv: Make VM_WRITE imply VM_READ Link: https://lore.kernel.org/r/20220915193702.2201018-1-abrestic@rivosinc.com/ Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'arch/riscv')
-rw-r--r--arch/riscv/kernel/sys_riscv.c3
-rw-r--r--arch/riscv/mm/fault.c3
2 files changed, 2 insertions, 4 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));
}
diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
index f2fbd1400b7c..d86f7cebd4a7 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;