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

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Commit 8aeb7b17f0 ("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: 8aeb7b17f0 ("RISC-V: Make mmap() with PROT_WRITE imply PROT_READ")
Signed-off-by: Hsieh-Tseng Shen <woodrow.shen@sifive.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20230425102828.1616812-1-woodrow.shen@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Hsieh-Tseng Shen 2023-04-25 18:28:28 +08:00 committed by Palmer Dabbelt
parent 6966d7988c
commit 6569fc12e4
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GPG Key ID: 2E1319F35FBB1889
2 changed files with 2 additions and 3 deletions
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3
arch/riscv/include/asm/pgtable.h
View File

@ -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

2
arch/riscv/mm/init.c
View File

@ -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,