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Peter Anvin" , "Andrew Morton" , "Liam R. Howlett" , "Vlastimil Babka" , "Lorenzo Stoakes" , "Paul Walmsley" , "Palmer Dabbelt" , "Albert Ou" , "Conor Dooley" , "Rob Herring" , "Krzysztof Kozlowski" , "Arnd Bergmann" , "Christian Brauner" , "Peter Zijlstra" , "Oleg Nesterov" , "Eric Biederman" , "Kees Cook" , "Jonathan Corbet" , "Shuah Khan" , "Jann Horn" , "Conor Dooley" From: =?utf-8?q?Radim_Kr=C4=8Dm=C3=A1=C5=99?= References: <20250314-v5_user_cfi_series-v12-0-e51202b53138@rivosinc.com> <20250314-v5_user_cfi_series-v12-6-e51202b53138@rivosinc.com> In-Reply-To: <20250314-v5_user_cfi_series-v12-6-e51202b53138@rivosinc.com> 2025-03-14T14:39:25-07:00, Deepak Gupta : > diff --git a/arch/riscv/include/asm/mman.h b/arch/riscv/include/asm/mman.= h > +static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot, > + unsigned long pkey __always_unused) > +{ > + unsigned long ret =3D 0; > + > + /* > + * If PROT_WRITE was specified, force it to VM_READ | VM_WRITE. > + * Only VM_WRITE means shadow stack. > + */ This function also changes PROT_WX to VM_RWX, which is effectively not changing anything, but I think it deserves an explicit intent. (At least in the commit message.) > + if (prot & PROT_WRITE) > + ret =3D (VM_READ | VM_WRITE); > + return ret; > +} > diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.= c > @@ -16,6 +17,15 @@ static long riscv_sys_mmap(unsigned long addr, unsigne= d long len, > + /* > + * If PROT_WRITE is specified then extend that to PROT_READ > + * protection_map[VM_WRITE] is now going to select shadow stack encodin= gs. > + * So specifying PROT_WRITE actually should select protection_map [VM_W= RITE | VM_READ] > + * If user wants to create shadow stack then they should use `map_shado= w_stack` syscall. > + */ > + if (unlikely((prot & PROT_WRITE) && !(prot & PROT_READ))) > + prot |=3D PROT_READ; Why isn't the previous hunk be enough? (Or why don't we do just this?) riscv_sys_mmap() eventually calls arch_calc_vm_prot_bits(), so I'd rather fix each code path just once. Thanks.