Commit 9cac853e authored by Denis Vlasenko's avatar Denis Vlasenko Committed by Linus Torvalds

[PATCH] reduce stack consumption in load_elf_binary

Stack usage is reduced from 268 to 120 bytes on i386.
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent af4ffa17
...@@ -488,25 +488,33 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs) ...@@ -488,25 +488,33 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
unsigned long elf_entry, interp_load_addr = 0; unsigned long elf_entry, interp_load_addr = 0;
unsigned long start_code, end_code, start_data, end_data; unsigned long start_code, end_code, start_data, end_data;
unsigned long reloc_func_desc = 0; unsigned long reloc_func_desc = 0;
struct elfhdr elf_ex;
struct elfhdr interp_elf_ex;
struct exec interp_ex;
char passed_fileno[6]; char passed_fileno[6];
struct files_struct *files; struct files_struct *files;
int have_pt_gnu_stack, executable_stack = EXSTACK_DEFAULT; int have_pt_gnu_stack, executable_stack = EXSTACK_DEFAULT;
unsigned long def_flags = 0; unsigned long def_flags = 0;
struct {
struct elfhdr elf_ex;
struct elfhdr interp_elf_ex;
struct exec interp_ex;
} *loc;
loc = kmalloc(sizeof(*loc), GFP_KERNEL);
if (!loc) {
retval = -ENOMEM;
goto out_ret;
}
/* Get the exec-header */ /* Get the exec-header */
elf_ex = *((struct elfhdr *) bprm->buf); loc->elf_ex = *((struct elfhdr *) bprm->buf);
retval = -ENOEXEC; retval = -ENOEXEC;
/* First of all, some simple consistency checks */ /* First of all, some simple consistency checks */
if (memcmp(elf_ex.e_ident, ELFMAG, SELFMAG) != 0) if (memcmp(loc->elf_ex.e_ident, ELFMAG, SELFMAG) != 0)
goto out; goto out;
if (elf_ex.e_type != ET_EXEC && elf_ex.e_type != ET_DYN) if (loc->elf_ex.e_type != ET_EXEC && loc->elf_ex.e_type != ET_DYN)
goto out; goto out;
if (!elf_check_arch(&elf_ex)) if (!elf_check_arch(&loc->elf_ex))
goto out; goto out;
if (!bprm->file->f_op||!bprm->file->f_op->mmap) if (!bprm->file->f_op||!bprm->file->f_op->mmap)
goto out; goto out;
...@@ -514,16 +522,16 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs) ...@@ -514,16 +522,16 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
/* Now read in all of the header information */ /* Now read in all of the header information */
retval = -ENOMEM; retval = -ENOMEM;
if (elf_ex.e_phentsize != sizeof(struct elf_phdr)) if (loc->elf_ex.e_phentsize != sizeof(struct elf_phdr))
goto out; goto out;
if (elf_ex.e_phnum > 65536U / sizeof(struct elf_phdr)) if (loc->elf_ex.e_phnum > 65536U / sizeof(struct elf_phdr))
goto out; goto out;
size = elf_ex.e_phnum * sizeof(struct elf_phdr); size = loc->elf_ex.e_phnum * sizeof(struct elf_phdr);
elf_phdata = (struct elf_phdr *) kmalloc(size, GFP_KERNEL); elf_phdata = (struct elf_phdr *) kmalloc(size, GFP_KERNEL);
if (!elf_phdata) if (!elf_phdata)
goto out; goto out;
retval = kernel_read(bprm->file, elf_ex.e_phoff, (char *) elf_phdata, size); retval = kernel_read(bprm->file, loc->elf_ex.e_phoff, (char *) elf_phdata, size);
if (retval < 0) if (retval < 0)
goto out_free_ph; goto out_free_ph;
...@@ -554,7 +562,7 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs) ...@@ -554,7 +562,7 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
start_data = 0; start_data = 0;
end_data = 0; end_data = 0;
for (i = 0; i < elf_ex.e_phnum; i++) { for (i = 0; i < loc->elf_ex.e_phnum; i++) {
if (elf_ppnt->p_type == PT_INTERP) { if (elf_ppnt->p_type == PT_INTERP) {
/* This is the program interpreter used for /* This is the program interpreter used for
* shared libraries - for now assume that this * shared libraries - for now assume that this
...@@ -601,7 +609,7 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs) ...@@ -601,7 +609,7 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
* switch really is going to happen - do this in * switch really is going to happen - do this in
* flush_thread(). - akpm * flush_thread(). - akpm
*/ */
SET_PERSONALITY(elf_ex, ibcs2_interpreter); SET_PERSONALITY(loc->elf_ex, ibcs2_interpreter);
interpreter = open_exec(elf_interpreter); interpreter = open_exec(elf_interpreter);
retval = PTR_ERR(interpreter); retval = PTR_ERR(interpreter);
...@@ -612,15 +620,15 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs) ...@@ -612,15 +620,15 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
goto out_free_dentry; goto out_free_dentry;
/* Get the exec headers */ /* Get the exec headers */
interp_ex = *((struct exec *) bprm->buf); loc->interp_ex = *((struct exec *) bprm->buf);
interp_elf_ex = *((struct elfhdr *) bprm->buf); loc->interp_elf_ex = *((struct elfhdr *) bprm->buf);
break; break;
} }
elf_ppnt++; elf_ppnt++;
} }
elf_ppnt = elf_phdata; elf_ppnt = elf_phdata;
for (i = 0; i < elf_ex.e_phnum; i++, elf_ppnt++) for (i = 0; i < loc->elf_ex.e_phnum; i++, elf_ppnt++)
if (elf_ppnt->p_type == PT_GNU_STACK) { if (elf_ppnt->p_type == PT_GNU_STACK) {
if (elf_ppnt->p_flags & PF_X) if (elf_ppnt->p_flags & PF_X)
executable_stack = EXSTACK_ENABLE_X; executable_stack = EXSTACK_ENABLE_X;
...@@ -628,19 +636,19 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs) ...@@ -628,19 +636,19 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
executable_stack = EXSTACK_DISABLE_X; executable_stack = EXSTACK_DISABLE_X;
break; break;
} }
have_pt_gnu_stack = (i < elf_ex.e_phnum); have_pt_gnu_stack = (i < loc->elf_ex.e_phnum);
/* Some simple consistency checks for the interpreter */ /* Some simple consistency checks for the interpreter */
if (elf_interpreter) { if (elf_interpreter) {
interpreter_type = INTERPRETER_ELF | INTERPRETER_AOUT; interpreter_type = INTERPRETER_ELF | INTERPRETER_AOUT;
/* Now figure out which format our binary is */ /* Now figure out which format our binary is */
if ((N_MAGIC(interp_ex) != OMAGIC) && if ((N_MAGIC(loc->interp_ex) != OMAGIC) &&
(N_MAGIC(interp_ex) != ZMAGIC) && (N_MAGIC(loc->interp_ex) != ZMAGIC) &&
(N_MAGIC(interp_ex) != QMAGIC)) (N_MAGIC(loc->interp_ex) != QMAGIC))
interpreter_type = INTERPRETER_ELF; interpreter_type = INTERPRETER_ELF;
if (memcmp(interp_elf_ex.e_ident, ELFMAG, SELFMAG) != 0) if (memcmp(loc->interp_elf_ex.e_ident, ELFMAG, SELFMAG) != 0)
interpreter_type &= ~INTERPRETER_ELF; interpreter_type &= ~INTERPRETER_ELF;
retval = -ELIBBAD; retval = -ELIBBAD;
...@@ -656,11 +664,11 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs) ...@@ -656,11 +664,11 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
} }
/* Verify the interpreter has a valid arch */ /* Verify the interpreter has a valid arch */
if ((interpreter_type == INTERPRETER_ELF) && if ((interpreter_type == INTERPRETER_ELF) &&
!elf_check_arch(&interp_elf_ex)) !elf_check_arch(&loc->interp_elf_ex))
goto out_free_dentry; goto out_free_dentry;
} else { } else {
/* Executables without an interpreter also need a personality */ /* Executables without an interpreter also need a personality */
SET_PERSONALITY(elf_ex, ibcs2_interpreter); SET_PERSONALITY(loc->elf_ex, ibcs2_interpreter);
} }
/* OK, we are done with that, now set up the arg stuff, /* OK, we are done with that, now set up the arg stuff,
...@@ -700,8 +708,8 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs) ...@@ -700,8 +708,8 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
/* Do this immediately, since STACK_TOP as used in setup_arg_pages /* Do this immediately, since STACK_TOP as used in setup_arg_pages
may depend on the personality. */ may depend on the personality. */
SET_PERSONALITY(elf_ex, ibcs2_interpreter); SET_PERSONALITY(loc->elf_ex, ibcs2_interpreter);
if (elf_read_implies_exec(elf_ex, have_pt_gnu_stack)) if (elf_read_implies_exec(loc->elf_ex, have_pt_gnu_stack))
current->personality |= READ_IMPLIES_EXEC; current->personality |= READ_IMPLIES_EXEC;
arch_pick_mmap_layout(current->mm); arch_pick_mmap_layout(current->mm);
...@@ -723,7 +731,7 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs) ...@@ -723,7 +731,7 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
the image should be loaded at fixed address, not at a variable the image should be loaded at fixed address, not at a variable
address. */ address. */
for(i = 0, elf_ppnt = elf_phdata; i < elf_ex.e_phnum; i++, elf_ppnt++) { for(i = 0, elf_ppnt = elf_phdata; i < loc->elf_ex.e_phnum; i++, elf_ppnt++) {
int elf_prot = 0, elf_flags; int elf_prot = 0, elf_flags;
unsigned long k, vaddr; unsigned long k, vaddr;
...@@ -758,9 +766,9 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs) ...@@ -758,9 +766,9 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
elf_flags = MAP_PRIVATE|MAP_DENYWRITE|MAP_EXECUTABLE; elf_flags = MAP_PRIVATE|MAP_DENYWRITE|MAP_EXECUTABLE;
vaddr = elf_ppnt->p_vaddr; vaddr = elf_ppnt->p_vaddr;
if (elf_ex.e_type == ET_EXEC || load_addr_set) { if (loc->elf_ex.e_type == ET_EXEC || load_addr_set) {
elf_flags |= MAP_FIXED; elf_flags |= MAP_FIXED;
} else if (elf_ex.e_type == ET_DYN) { } else if (loc->elf_ex.e_type == ET_DYN) {
/* Try and get dynamic programs out of the way of the default mmap /* Try and get dynamic programs out of the way of the default mmap
base, as well as whatever program they might try to exec. This base, as well as whatever program they might try to exec. This
is because the brk will follow the loader, and is not movable. */ is because the brk will follow the loader, and is not movable. */
...@@ -774,7 +782,7 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs) ...@@ -774,7 +782,7 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
if (!load_addr_set) { if (!load_addr_set) {
load_addr_set = 1; load_addr_set = 1;
load_addr = (elf_ppnt->p_vaddr - elf_ppnt->p_offset); load_addr = (elf_ppnt->p_vaddr - elf_ppnt->p_offset);
if (elf_ex.e_type == ET_DYN) { if (loc->elf_ex.e_type == ET_DYN) {
load_bias += error - load_bias += error -
ELF_PAGESTART(load_bias + vaddr); ELF_PAGESTART(load_bias + vaddr);
load_addr += load_bias; load_addr += load_bias;
...@@ -811,7 +819,7 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs) ...@@ -811,7 +819,7 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
elf_brk = k; elf_brk = k;
} }
elf_ex.e_entry += load_bias; loc->elf_ex.e_entry += load_bias;
elf_bss += load_bias; elf_bss += load_bias;
elf_brk += load_bias; elf_brk += load_bias;
start_code += load_bias; start_code += load_bias;
...@@ -833,10 +841,10 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs) ...@@ -833,10 +841,10 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
if (elf_interpreter) { if (elf_interpreter) {
if (interpreter_type == INTERPRETER_AOUT) if (interpreter_type == INTERPRETER_AOUT)
elf_entry = load_aout_interp(&interp_ex, elf_entry = load_aout_interp(&loc->interp_ex,
interpreter); interpreter);
else else
elf_entry = load_elf_interp(&interp_elf_ex, elf_entry = load_elf_interp(&loc->interp_elf_ex,
interpreter, interpreter,
&interp_load_addr); &interp_load_addr);
if (BAD_ADDR(elf_entry)) { if (BAD_ADDR(elf_entry)) {
...@@ -851,7 +859,7 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs) ...@@ -851,7 +859,7 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
fput(interpreter); fput(interpreter);
kfree(elf_interpreter); kfree(elf_interpreter);
} else { } else {
elf_entry = elf_ex.e_entry; elf_entry = loc->elf_ex.e_entry;
} }
kfree(elf_phdata); kfree(elf_phdata);
...@@ -863,7 +871,7 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs) ...@@ -863,7 +871,7 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
compute_creds(bprm); compute_creds(bprm);
current->flags &= ~PF_FORKNOEXEC; current->flags &= ~PF_FORKNOEXEC;
create_elf_tables(bprm, &elf_ex, (interpreter_type == INTERPRETER_AOUT), create_elf_tables(bprm, &loc->elf_ex, (interpreter_type == INTERPRETER_AOUT),
load_addr, interp_load_addr); load_addr, interp_load_addr);
/* N.B. passed_fileno might not be initialized? */ /* N.B. passed_fileno might not be initialized? */
if (interpreter_type == INTERPRETER_AOUT) if (interpreter_type == INTERPRETER_AOUT)
...@@ -908,6 +916,8 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs) ...@@ -908,6 +916,8 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
} }
retval = 0; retval = 0;
out: out:
kfree(loc);
out_ret:
return retval; return retval;
/* error cleanup */ /* error cleanup */
......
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