mm: variable length argument support

Remove the arg+env limit of MAX_ARG_PAGES by copying the strings directly from
the old mm into the new mm.

We create the new mm before the binfmt code runs, and place the new stack at
the very top of the address space.  Once the binfmt code runs and figures out
where the stack should be, we move it downwards.

It is a bit peculiar in that we have one task with two mm's, one of which is
inactive.

[a.p.zijlstra@chello.nl: limit stack size]
Signed-off-by: Ollie Wild <aaw@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <linux-arch@vger.kernel.org>
Cc: Hugh Dickins <hugh@veritas.com>
[bunk@stusta.de: unexport bprm_mm_init]
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 9d62fbad3d4b..4739506fb083 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -621,8 +621,8 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
         p = (char __user *) current->mm->arg_start;
         for (loop = bprm->argc; loop > 0; loop--) {
                 __put_user((elf_caddr_t) p, argv++);
-                len = strnlen_user(p, PAGE_SIZE * MAX_ARG_PAGES);
-                if (!len || len > PAGE_SIZE * MAX_ARG_PAGES)
+                len = strnlen_user(p, MAX_ARG_STRLEN);
+                if (!len || len > MAX_ARG_STRLEN)
                         return -EINVAL;
                 p += len;
         }
@@ -633,8 +633,8 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
         current->mm->env_start = (unsigned long) p;
         for (loop = bprm->envc; loop > 0; loop--) {
                 __put_user((elf_caddr_t)(unsigned long) p, envp++);
-                len = strnlen_user(p, PAGE_SIZE * MAX_ARG_PAGES);
-                if (!len || len > PAGE_SIZE * MAX_ARG_PAGES)
+                len = strnlen_user(p, MAX_ARG_STRLEN);
+                if (!len || len > MAX_ARG_STRLEN)
                         return -EINVAL;
                 p += len;
         }