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hurd: Fix restoring reply port in sigreturn

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We must not use the user's reply port (scp->sc_reply_port) for any of
our own RPCs, otherwise various things break. So, use MACH_PORT_DEAD as
a reply port when destroying our reply port, and make sure to do this
after _hurd_sigstate_unlock (), which may do a gsync_wake () RPC.

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
This commit is contained in:
Sergey Bugaev 2023-04-14 22:36:56 +03:00 • committed by Samuel Thibault
parent 060cadaab6
commit e411e31b7b
1 changed files with 23 additions and 12 deletions
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35
sysdeps/mach/hurd/i386/sigreturn.c
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@ -26,11 +26,29 @@ register int *sp asm ("%esp");
/* This is run on the thread stack after restoring it, to be able to
unlock SS off sigstack. */
static void
__sigreturn2 (int *usp)
__sigreturn2 (int *usp, struct sigcontext *scp)
{
mach_port_t reply_port;
struct hurd_sigstate *ss = _hurd_self_sigstate ();
_hurd_sigstate_unlock (ss);
/* Destroy the MiG reply port used by the signal handler, and restore the
reply port in use by the thread when interrupted.
We cannot use the original reply port for our RPCs that we do here, since
we could unexpectedly receive/consume a reply message meant for the user
(in particular, msg_sig_post_reply), and also since we would deallocate
the port if *our* RPC fails, which we don't want to do since the user
still has the old name. And so, temporarily set MACH_PORT_DEAD as our
reply name, and make sure destroying the port is the very last RPC we
do. */
reply_port = THREAD_GETMEM (THREAD_SELF, reply_port);
THREAD_SETMEM (THREAD_SELF, reply_port, MACH_PORT_DEAD);
if (MACH_PORT_VALID (reply_port))
(void) __mach_port_mod_refs (__mach_task_self (), reply_port,
MACH_PORT_RIGHT_RECEIVE, -1);
THREAD_SETMEM (THREAD_SELF, reply_port, scp->sc_reply_port);
sp = usp;
#define A(line) asm volatile (#line)
/* The members in the sigcontext are arranged in this order
@ -58,7 +76,6 @@ __sigreturn (struct sigcontext *scp)
{
struct hurd_sigstate *ss;
struct hurd_userlink *link = (void *) &scp[1];
mach_port_t reply_port;
if (scp == NULL || (scp->sc_mask & _SIG_CANT_MASK))
{
@ -98,13 +115,6 @@ __sigreturn (struct sigcontext *scp)
if (scp->sc_onstack)
ss->sigaltstack.ss_flags &= ~SS_ONSTACK;
/* Destroy the MiG reply port used by the signal handler, and restore the
reply port in use by the thread when interrupted. */
reply_port = THREAD_GETMEM (THREAD_SELF, reply_port);
THREAD_SETMEM (THREAD_SELF, reply_port, scp->sc_reply_port);
if (MACH_PORT_VALID (reply_port))
__mach_port_destroy (__mach_task_self (), reply_port);
if (scp->sc_fpused)
/* Restore the FPU state. Mach conveniently stores the state
in the format the i387 `frstor' instruction uses to restore it. */
@ -115,15 +125,16 @@ __sigreturn (struct sigcontext *scp)
copy the registers onto the user's stack, switch there, pop and
return. */
int *usp = (int *) scp->sc_uesp;
int usp_arg, *usp = (int *) scp->sc_uesp;
*--usp = scp->sc_eip;
*--usp = scp->sc_efl;
memcpy (usp -= 12, &scp->sc_i386_thread_state, 12 * sizeof (int));
usp_arg = (int) usp;
*--usp = (int) scp;
/* Pass usp to __sigreturn2 so it can unwind itself easily. */
*(usp-1) = (int) usp;
--usp;
*--usp = usp_arg;
/* Bogus return address for __sigreturn2 */
*--usp = 0;
*--usp = (int) __sigreturn2;