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binfmt_flat: clean up create_flat_tables() and stack accesses

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In addition to better code clarity, this brings proper usage of
user memory accessors everywhere the stack is touched. This is essential
for making this work on MMU systems.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Reviewed-by: Greg Ungerer <gerg@linux-m68k.org>
Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>
This commit is contained in:
Nicolas Pitre 2016-07-24 11:30:20 -04:00 committed by Greg Ungerer
parent 687fd7738e
commit a97d157d00
1 changed files with 58 additions and 49 deletions
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107
fs/binfmt_flat.c
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@ -103,50 +103,58 @@ static int flat_core_dump(struct coredump_params *cprm)
/*
* create_flat_tables() parses the env- and arg-strings in new user
* memory and creates the pointer tables from them, and puts their
* addresses on the "stack", returning the new stack pointer value.
* addresses on the "stack", recording the new stack pointer value.
*/
static unsigned long create_flat_tables(
unsigned long pp,
struct linux_binprm *bprm)
static int create_flat_tables(struct linux_binprm *bprm, unsigned long arg_start)
{
unsigned long *argv, *envp;
unsigned long *sp;
char *p = (char *)pp;
int argc = bprm->argc;
int envc = bprm->envc;
char uninitialized_var(dummy);
char __user *p;
unsigned long __user *sp;
long i, len;
sp = (unsigned long *)p;
sp -= (envc + argc + 2) + 1 + (flat_argvp_envp_on_stack() ? 2 : 0);
sp = (unsigned long *) ((unsigned long)sp & -FLAT_STACK_ALIGN);
argv = sp + 1 + (flat_argvp_envp_on_stack() ? 2 : 0);
envp = argv + (argc + 1);
p = (char __user *)arg_start;
sp = (unsigned long __user *)current->mm->start_stack;
sp -= bprm->envc + 1;
sp -= bprm->argc + 1;
sp -= flat_argvp_envp_on_stack() ? 2 : 0;
sp -= 1; /* &argc */
current->mm->start_stack = (unsigned long)sp & -FLAT_STACK_ALIGN;
sp = (unsigned long __user *)current->mm->start_stack;
__put_user(bprm->argc, sp++);
if (flat_argvp_envp_on_stack()) {
put_user((unsigned long) envp, sp + 2);
put_user((unsigned long) argv, sp + 1);
unsigned long argv, envp;
argv = (unsigned long)(sp + 2);
envp = (unsigned long)(sp + 2 + bprm->argc + 1);
__put_user(argv, sp++);
__put_user(envp, sp++);
}
put_user(argc, sp);
current->mm->arg_start = (unsigned long) p;
while (argc-- > 0) {
put_user((unsigned long) p, argv++);
do {
get_user(dummy, p); p++;
} while (dummy);
current->mm->arg_start = (unsigned long)p;
for (i = bprm->argc; i > 0; i--) {
__put_user((unsigned long)p, sp++);
len = strnlen_user(p, MAX_ARG_STRLEN);
if (!len || len > MAX_ARG_STRLEN)
return -EINVAL;
p += len;
}
put_user((unsigned long) NULL, argv);
current->mm->arg_end = current->mm->env_start = (unsigned long) p;
while (envc-- > 0) {
put_user((unsigned long)p, envp); envp++;
do {
get_user(dummy, p); p++;
} while (dummy);
__put_user(0, sp++);
current->mm->arg_end = (unsigned long)p;
current->mm->env_start = (unsigned long) p;
for (i = bprm->envc; i > 0; i--) {
__put_user((unsigned long)p, sp++);
len = strnlen_user(p, MAX_ARG_STRLEN);
if (!len || len > MAX_ARG_STRLEN)
return -EINVAL;
p += len;
}
put_user((unsigned long) NULL, envp);
current->mm->env_end = (unsigned long) p;
return (unsigned long)sp;
__put_user(0, sp++);
current->mm->env_end = (unsigned long)p;
return 0;
}
/****************************************************************************/
@ -846,7 +854,7 @@ static int load_flat_binary(struct linux_binprm *bprm)
{
struct lib_info libinfo;
struct pt_regs *regs = current_pt_regs();
unsigned long sp, stack_len;
unsigned long stack_len;
unsigned long start_addr;
int res;
int i, j;
@ -860,11 +868,10 @@ static int load_flat_binary(struct linux_binprm *bprm)
* pedantic and include space for the argv/envp array as it may have
* a lot of entries.
*/
#define TOP_OF_ARGS (PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *))
stack_len = TOP_OF_ARGS - bprm->p; /* the strings */
stack_len += (bprm->argc + 1) * sizeof(char *); /* the argv array */
stack_len += (bprm->envc + 1) * sizeof(char *); /* the envp array */
stack_len += FLAT_STACK_ALIGN - 1; /* reserve for upcoming alignment */
stack_len = PAGE_SIZE * MAX_ARG_PAGES - bprm->p; /* the strings */
stack_len += (bprm->argc + 1) * sizeof(char *); /* the argv array */
stack_len += (bprm->envc + 1) * sizeof(char *); /* the envp array */
stack_len = ALIGN(stack_len, FLAT_STACK_ALIGN);
res = load_flat_file(bprm, &libinfo, 0, &stack_len);
if (res < 0)
@ -882,16 +889,18 @@ static int load_flat_binary(struct linux_binprm *bprm)
set_binfmt(&flat_format);
sp = ((current->mm->context.end_brk + stack_len + 3) & ~3) - 4;
pr_debug("sp=%lx\n", sp);
/* Stash our initial stack pointer into the mm structure */
current->mm->start_stack =
((current->mm->context.end_brk + stack_len + 3) & ~3) - 4;
pr_debug("sp=%lx\n", current->mm->start_stack);
/* copy the arg pages onto the stack */
res = transfer_args_to_stack(bprm, &sp);
res = transfer_args_to_stack(bprm, &current->mm->start_stack);
if (!res)
res = create_flat_tables(bprm, current->mm->start_stack);
if (res)
return res;
sp = create_flat_tables(sp, bprm);
/* Fake some return addresses to ensure the call chain will
* initialise library in order for us. We are required to call
* lib 1 first, then 2, ... and finally the main program (id 0).
@ -902,15 +911,15 @@ static int load_flat_binary(struct linux_binprm *bprm)
for (i = MAX_SHARED_LIBS-1; i > 0; i--) {
if (libinfo.lib_list[i].loaded) {
/* Push previos first to call address */
--sp; put_user(start_addr, (unsigned long *)sp);
unsigned long __user *sp;
current->mm->start_stack -= sizeof(unsigned long);
sp = (unsigned long __user *)current->mm->start_stack;
__put_user(start_addr, sp);
start_addr = libinfo.lib_list[i].entry;
}
}
#endif
/* Stash our initial stack pointer into the mm structure */
current->mm->start_stack = sp;
#ifdef FLAT_PLAT_INIT
FLAT_PLAT_INIT(regs);
#endif