Unverified Commit 6569fc12 authored by Hsieh-Tseng Shen's avatar Hsieh-Tseng Shen Committed by Palmer Dabbelt
Browse files

riscv: mm: Ensure prot of VM_WRITE and VM_EXEC must be readable 



Commit 8aeb7b17 ("RISC-V: Make mmap() with PROT_WRITE imply PROT_READ")
allows riscv to use mmap with PROT_WRITE only, and meanwhile mmap with w+x
is also permitted. However, when userspace tries to access this page with
PROT_WRITE|PROT_EXEC, which causes infinite loop at load page fault as
well as it triggers soft lockup. According to riscv privileged spec,
"Writable pages must also be marked readable". The fix to drop the
`PAGE_COPY_READ_EXEC` and then `PAGE_COPY_EXEC` would be just used instead.
This aligns the other arches (i.e arm64) for protection_map.

Fixes: 8aeb7b17 ("RISC-V: Make mmap() with PROT_WRITE imply PROT_READ")
Signed-off-by: default avatarHsieh-Tseng Shen <woodrow.shen@sifive.com>
Reviewed-by: default avatarAlexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20230425102828.1616812-1-woodrow.shen@sifive.com


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent 6966d798

arch/riscv/include/asm/pgtable.h

+1 −2
Original line number Diff line number Diff line
@@ -165,8 +165,7 @@ extern struct pt_alloc_ops pt_ops __initdata; 
					 _PAGE_EXEC | _PAGE_WRITE)



#define PAGE_COPY		PAGE_READ

#define PAGE_COPY_EXEC		PAGE_EXEC

#define PAGE_COPY_READ_EXEC	PAGE_READ_EXEC

#define PAGE_COPY_EXEC		PAGE_READ_EXEC

#define PAGE_SHARED		PAGE_WRITE

#define PAGE_SHARED_EXEC	PAGE_WRITE_EXEC

arch/riscv/mm/init.c

+1 −1
Original line number Diff line number Diff line
@@ -293,7 +293,7 @@ static const pgprot_t protection_map[16] = { 
	[VM_EXEC]					= PAGE_EXEC,

	[VM_EXEC | VM_READ]				= PAGE_READ_EXEC,

	[VM_EXEC | VM_WRITE]				= PAGE_COPY_EXEC,

	[VM_EXEC | VM_WRITE | VM_READ]			= PAGE_COPY_READ_EXEC,

	[VM_EXEC | VM_WRITE | VM_READ]			= PAGE_COPY_EXEC,

	[VM_SHARED]					= PAGE_NONE,

	[VM_SHARED | VM_READ]				= PAGE_READ,

	[VM_SHARED | VM_WRITE]				= PAGE_SHARED,