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Avoid init stack top at MAX_USERSPACE_VADDR

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Marsman1996 2024-11-13 21:34:34 +08:00 committed by Tate, Hongliang Tian
parent 85d2c9634f
commit c200997c9a
1 changed files with 11 additions and 3 deletions
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14
kernel/src/process/process_vm/init_stack/mod.rs
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@ -121,9 +121,17 @@ impl Clone for InitStack {
impl InitStack { impl InitStack {
pub(super) fn new() -> Self { pub(super) fn new() -> Self {
let nr_pages_padding = { let nr_pages_padding = {
let mut random_nr_pages_padding: u8 = 0; // We do not want the stack top too close to MAX_USERSPACE_VADDR.
getrandom(random_nr_pages_padding.as_bytes_mut()).unwrap(); // So we add this fixed padding. Any small value greater than zero will do.
random_nr_pages_padding as usize const NR_FIXED_PADDING_PAGES: usize = 7;
// Some random padding pages are added as a simple measure to
// make the stack values of a buggy user program harder
// to be exploited by attackers.
let mut nr_random_padding_pages: u8 = 0;
getrandom(nr_random_padding_pages.as_bytes_mut()).unwrap();
nr_random_padding_pages as usize + NR_FIXED_PADDING_PAGES
}; };
let initial_top = MAX_USERSPACE_VADDR - PAGE_SIZE * nr_pages_padding; let initial_top = MAX_USERSPACE_VADDR - PAGE_SIZE * nr_pages_padding;
let max_size = INIT_STACK_SIZE; let max_size = INIT_STACK_SIZE;