diff options
| author | H.J. Lu <hjl.tools@gmail.com> | 2018-07-24 05:20:48 -0700 |
|---|---|---|
| committer | H.J. Lu <hjl.tools@gmail.com> | 2018-07-24 05:21:07 -0700 |
| commit | 3650e1d9284926be67e368707a9a2276fb77a167 (patch) | |
| tree | e278a6deadd6d347e1446104bbea53144045ba7a /sysdeps/unix/sysv/linux/x86_64 | |
| parent | ca027e0f62789a0958b69dac4133616a90de6f7c (diff) | |
| download | glibc-3650e1d9284926be67e368707a9a2276fb77a167.tar.gz glibc-3650e1d9284926be67e368707a9a2276fb77a167.tar.xz glibc-3650e1d9284926be67e368707a9a2276fb77a167.zip | |
x86: Update vfork to pop shadow stack
The shadow stack prevents us from pushing the saved return PC onto the stack and returning normally. Instead we pop the shadow stack and return directly. This is the safest way to return and ensures any stack manipulations done by the vfork'd child doesn't cause the parent to terminate when CET is enabled. Reviewed-by: Carlos O'Donell <carlos@redhat.com> * sysdeps/unix/sysv/linux/i386/vfork.S (SYSCALL_ERROR_HANDLER): Redefine if shadow stack is enabled. (SYSCALL_ERROR_LABEL): Likewise. (__vfork): Pop shadow stack and jump back to to caller directly when shadow stack is in use. * sysdeps/unix/sysv/linux/x86_64/vfork.S (SYSCALL_ERROR_HANDLER): Redefine if shadow stack is enabled. (SYSCALL_ERROR_LABEL): Likewise. (__vfork): Pop shadow stack and jump back to to caller directly when shadow stack is in use.
Diffstat (limited to 'sysdeps/unix/sysv/linux/x86_64')
| -rw-r--r-- | sysdeps/unix/sysv/linux/x86_64/vfork.S | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/x86_64/vfork.S b/sysdeps/unix/sysv/linux/x86_64/vfork.S index e4c8269e3d..8f1ca9f836 100644 --- a/sysdeps/unix/sysv/linux/x86_64/vfork.S +++ b/sysdeps/unix/sysv/linux/x86_64/vfork.S @@ -20,6 +20,21 @@ #include <bits/errno.h> #include <tcb-offsets.h> +#if SHSTK_ENABLED +/* The shadow stack prevents us from pushing the saved return PC onto + the stack and returning normally. Instead we pop the shadow stack + and return directly. This is the safest way to return and ensures + any stack manipulations done by the vfork'd child doesn't cause the + parent to terminate when CET is enabled. */ +# undef SYSCALL_ERROR_HANDLER +# define SYSCALL_ERROR_HANDLER \ +0: \ + SYSCALL_SET_ERRNO; \ + or $-1, %RAX_LP; \ + jmp 1b; +# undef SYSCALL_ERROR_LABEL +# define SYSCALL_ERROR_LABEL 0f +#endif /* Clone the calling process, but without copying the whole address space. The calling process is suspended until the new process exits or is @@ -38,13 +53,36 @@ ENTRY (__vfork) movl $SYS_ify (vfork), %eax syscall +#if !SHSTK_ENABLED /* Push back the return PC. */ pushq %rdi cfi_adjust_cfa_offset(8) +#endif cmpl $-4095, %eax jae SYSCALL_ERROR_LABEL /* Branch forward if it failed. */ +#if SHSTK_ENABLED +1: + /* Check if shadow stack is in use. */ + xorl %esi, %esi + rdsspq %rsi + testq %rsi, %rsi + /* Normal return if shadow stack isn't in use. */ + je L(no_shstk) + + /* Pop return address from shadow stack and jump back to caller + directly. */ + movl $1, %esi + incsspq %rsi + jmp *%rdi + +L(no_shstk): + /* Push back the return PC. */ + pushq %rdi + cfi_adjust_cfa_offset(8) +#endif + /* Normal return. */ ret |