Commit da029c11 authored by Kees Cook's avatar Kees Cook Committed by Linus Torvalds

exec: Limit arg stack to at most 75% of _STK_LIM

To avoid pathological stack usage or the need to special-case setuid
execs, just limit all arg stack usage to at most 75% of _STK_LIM (6MB).
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 088737f4
......@@ -220,8 +220,7 @@ static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
if (write) {
unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
unsigned long ptr_size;
struct rlimit *rlim;
unsigned long ptr_size, limit;
/*
* Since the stack will hold pointers to the strings, we
......@@ -250,14 +249,16 @@ static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
return page;
/*
* Limit to 1/4-th the stack size for the argv+env strings.
* Limit to 1/4 of the max stack size or 3/4 of _STK_LIM
* (whichever is smaller) for the argv+env strings.
* This ensures that:
* - the remaining binfmt code will not run out of stack space,
* - the program will have a reasonable amount of stack left
* to work from.
*/
rlim = current->signal->rlim;
if (size > READ_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4)
limit = _STK_LIM / 4 * 3;
limit = min(limit, rlimit(RLIMIT_STACK) / 4);
if (size > limit)
goto fail;
}
......
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