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This commit is contained in:
Raoul Strackx 2022-06-22 13:47:32 +02:00
parent a27aaceee9
commit 6a6910e5a9
1 changed files with 10 additions and 5 deletions
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15
library/std/src/sys/sgx/abi/usercalls/alloc.rs
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@ -307,8 +307,9 @@ where
/// Copies `len` bytes of data from enclave pointer `src` to userspace `dst` /// Copies `len` bytes of data from enclave pointer `src` to userspace `dst`
/// ///
/// This function mitigates stale data vulnerabilities /// This function mitigates stale data vulnerabilities by ensuring all writes to untrusted memory are either:
/// https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00615.html /// - preceded by the VERW instruction and followed by the MFENCE; LFENCE instruction sequence
/// - or are in multiples of 8 bytes, aligned to an 8-byte boundary
/// ///
/// # Panics /// # Panics
/// This function panics if: /// This function panics if:
@ -317,10 +318,14 @@ where
/// * The `dst` pointer is null /// * The `dst` pointer is null
/// * The `src` memory range is not in enclave memory /// * The `src` memory range is not in enclave memory
/// * The `dst` memory range is not in user memory /// * The `dst` memory range is not in user memory
///
/// # References
/// - https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00615.html
/// - https://www.intel.com/content/www/us/en/developer/articles/technical/software-security-guidance/technical-documentation/processor-mmio-stale-data-vulnerabilities.html#inpage-nav-3-2-2
pub(crate) unsafe fn copy_to_userspace(src: *const u8, dst: *mut u8, len: usize) { pub(crate) unsafe fn copy_to_userspace(src: *const u8, dst: *mut u8, len: usize) {
unsafe fn copy_bytewise_to_userspace(src: *const u8, dst: *mut u8, len: usize) { unsafe fn copy_bytewise_to_userspace(src: *const u8, dst: *mut u8, len: usize) {
unsafe { unsafe {
let seg_sel: u16 = 0; let mut seg_sel: u16 = 0;
for off in 0..len { for off in 0..len {
asm!(" asm!("
mov %ds, ({seg_sel}) mov %ds, ({seg_sel})
@ -328,10 +333,10 @@ pub(crate) unsafe fn copy_to_userspace(src: *const u8, dst: *mut u8, len: usize)
movb {val}, ({dst}) movb {val}, ({dst})
mfence mfence
lfence lfence
", ",
val = in(reg_byte) *src.offset(off as isize), val = in(reg_byte) *src.offset(off as isize),
dst = in(reg) dst.offset(off as isize), dst = in(reg) dst.offset(off as isize),
seg_sel = in(reg) &seg_sel, seg_sel = in(reg) &mut seg_sel,
options(nostack, att_syntax) options(nostack, att_syntax)
); );
} }