As a preliminary step to AT_RANDOM alignment and randomization, replaces STACK_ macros by elf_stack_ inline functions to make them easier to reuse. STACK_ROUND() needed a pointer to elf_addr_t, while STACK_ADD() and STACK_ALLOC() don't. In the new functions, the current stack pointer is an obvious input/output parameter of unsigned long type. STACK_ADD() returned an unsigned long, while STACK_ROUND() returned a pointer to elf_addr_t. elf_stack_add_items() and elf_stack_align() return both void. STACK_ROUND() was used to reserve space on stack (like STACK_ADD()) and to align the resulting stack pointer on 16 bytes boundary. The macro is replaced by elf_stack_add_items() followed by elf_stack_align(). Link: https://lore.kernel.org/lkml/cover.1560423331.git.ydroneaud@xxxxxxxxxx Signed-off-by: Yann Droneaud <ydroneaud@xxxxxxxxxx> --- fs/binfmt_elf.c | 68 ++++++++++++++++++++++++++++++++++++------------- 1 file changed, 50 insertions(+), 18 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 8264b468f283..87f0c8a21350 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -136,21 +136,52 @@ static int padzero(unsigned long elf_bss) return 0; } -/* Let's use some macros to make this stack manipulation a little clearer */ +/* Let's use some functions to make this stack manipulation clearer */ +static inline void elf_stack_add_items(unsigned long *pp, size_t items) +{ + elf_addr_t *sp = (elf_addr_t *)*pp; + +#ifdef CONFIG_STACK_GROWSUP + sp += items; +#else + sp -= items; +#endif + + *pp = (unsigned long)sp; +} + +static inline void elf_stack_align(unsigned long *pp) +{ + unsigned long p = *pp; + +#ifdef CONFIG_STACK_GROWSUP + p += 15; +#endif + + p &= ~15UL; + + *pp = p; +} + +static inline elf_addr_t __user *elf_stack_alloc(unsigned long *pp, + size_t len) +{ + unsigned long p = *pp; + elf_addr_t __user *sp; + #ifdef CONFIG_STACK_GROWSUP -#define STACK_ADD(sp, items) ((elf_addr_t __user *)(sp) + (items)) -#define STACK_ROUND(sp, items) \ - ((15 + (unsigned long) ((sp) + (items))) &~ 15UL) -#define STACK_ALLOC(sp, len) ({ \ - elf_addr_t __user *old_sp = (elf_addr_t __user *)sp; sp += len; \ - old_sp; }) + sp = (elf_addr_t __user *)p; + p += len; #else -#define STACK_ADD(sp, items) ((elf_addr_t __user *)(sp) - (items)) -#define STACK_ROUND(sp, items) \ - (((unsigned long) (sp - items)) &~ 15UL) -#define STACK_ALLOC(sp, len) ({ sp -= len ; sp; }) + p -= len; + sp = (elf_addr_t __user *)p; #endif + *pp = p; + + return sp; +} + #ifndef ELF_BASE_PLATFORM /* * AT_BASE_PLATFORM indicates the "real" hardware/microarchitecture. @@ -198,7 +229,7 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec, if (k_platform) { size_t len = strlen(k_platform) + 1; - u_platform = (elf_addr_t __user *)STACK_ALLOC(p, len); + u_platform = elf_stack_alloc(&p, len); if (__copy_to_user(u_platform, k_platform, len)) return -EFAULT; } @@ -211,7 +242,7 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec, if (k_base_platform) { size_t len = strlen(k_base_platform) + 1; - u_base_platform = (elf_addr_t __user *)STACK_ALLOC(p, len); + u_base_platform = elf_stack_alloc(&p, len); if (__copy_to_user(u_base_platform, k_base_platform, len)) return -EFAULT; } @@ -220,8 +251,7 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec, * Generate 16 random bytes for userspace PRNG seeding. */ get_random_bytes(k_rand_bytes, sizeof(k_rand_bytes)); - u_rand_bytes = (elf_addr_t __user *) - STACK_ALLOC(p, sizeof(k_rand_bytes)); + u_rand_bytes = elf_stack_alloc(&p, sizeof(k_rand_bytes)); if (__copy_to_user(u_rand_bytes, k_rand_bytes, sizeof(k_rand_bytes))) return -EFAULT; @@ -280,11 +310,13 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec, /* And advance past the AT_NULL entry. */ ei_index += 2; - - sp = STACK_ADD(p, ei_index); + elf_stack_add_items(&p, ei_index); items = (argc + 1) + (envc + 1) + 1; - bprm->p = STACK_ROUND(sp, items); + elf_stack_add_items(&p, items); + elf_stack_align(&p); + + bprm->p = p; /* Point sp at the lowest address on the stack */ #ifdef CONFIG_STACK_GROWSUP -- 2.21.0