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hurd: Fix race between calling RPC and handling a signal 

* sysdeps/mach/hurd/i386/intr-msg.h (INTR_MSG_TRAP): Make
	_hurd_intr_rpc_msg_about_to global point to start of controlled
	assembly snippet. Make it check canceled flag.
	* hurd/hurdsig.c (_hurdsig_abort_rpcs): Only mutate thread if it passed
	the _hurd_intr_rpc_msg_about_to point.
	* hurd/intr-msg.c (_hurd_intr_rpc_mach_msg): Remove comment on mutation
	issue, remove cancel flag check.
This commit is contained in:
Samuel Thibault 2018-10-09 23:40:09 +02:00
parent 2d0d1d3876
commit 5c81be5340
4 changed files with 28 additions and 23 deletions
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7
ChangeLog
View File

@ -3,6 +3,13 @@
* hurd/hurdsig.c (_hurd_interrupted_rpc_timeout): Set to 60000.
* hurd/intr-msg.c (_hurd_intr_rpc_mach_msg): When the server does not
answer to interrupt_operation, return EIO instead of EINTR.
* sysdeps/mach/hurd/i386/intr-msg.h (INTR_MSG_TRAP): Make
_hurd_intr_rpc_msg_about_to global point to start of controlled
assembly snippet. Make it check canceled flag.
* hurd/hurdsig.c (_hurdsig_abort_rpcs): Only mutate thread if it passed
the _hurd_intr_rpc_msg_about_to point.
* hurd/intr-msg.c (_hurd_intr_rpc_mach_msg): Remove comment on mutation
issue, remove cancel flag check.
2018-10-26 Joseph Myers <joseph@codesourcery.com>

4
hurd/hurdsig.c
View File

@ -292,6 +292,7 @@ _hurdsig_abort_rpcs (struct hurd_sigstate *ss, int signo, int sigthread,
struct machine_thread_all_state *state, int *state_change,
void (*reply) (void))
{
extern const void _hurd_intr_rpc_msg_about_to;
extern const void _hurd_intr_rpc_msg_in_trap;
mach_port_t rcv_port = MACH_PORT_NULL;
mach_port_t intr_port;
@ -307,7 +308,8 @@ _hurdsig_abort_rpcs (struct hurd_sigstate *ss, int signo, int sigthread,
receive completes immediately or aborts. */
abort_thread (ss, state, reply);
if (state->basic.PC < (natural_t) &_hurd_intr_rpc_msg_in_trap)
if (state->basic.PC >= (natural_t) &_hurd_intr_rpc_msg_about_to &&
state->basic.PC < (natural_t) &_hurd_intr_rpc_msg_in_trap)
{
/* The thread is about to do the RPC, but hasn't yet entered
mach_msg. Mutate the thread's state so it knows not to try

17
hurd/intr-msg.c
View File

@ -114,23 +114,10 @@ _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
message:
/* XXX
At all points here (once SS->intr_port is set), the signal thread
thinks we are "about to enter the syscall", and might mutate our
return-value register. This is bogus.
*/
if (ss->cancel)
{
/* We have been cancelled. Don't do an RPC at all. */
ss->intr_port = MACH_PORT_NULL;
ss->cancel = 0;
return EINTR;
}
/* Note that the signal trampoline code might modify our OPTION! */
err = INTR_MSG_TRAP (msg, option, send_size,
rcv_size, rcv_name, timeout, notify);
rcv_size, rcv_name, timeout, notify,
&ss->cancel, &ss->intr_port);
switch (err)
{

23
sysdeps/mach/hurd/i386/intr-msg.h
View File

@ -20,21 +20,30 @@
/* Note that we must mark OPTION and TIMEOUT as outputs of this operation,
to indicate that the signal thread might mutate them as part
of sending us to a signal handler. */
#define INTR_MSG_TRAP(msg, option, send_size, rcv_size, rcv_name, timeout, notify) \
/* After _hurd_intr_rpc_msg_about_to we need to make a last check of cancel, in
case we got interrupted right before _hurd_intr_rpc_msg_about_to. */
#define INTR_MSG_TRAP(msg, option, send_size, rcv_size, rcv_name, timeout, notify, cancel_p, intr_port_p) \
({ \
error_t err; \
asm (".globl _hurd_intr_rpc_msg_do_trap\n" \
".globl _hurd_intr_rpc_msg_in_trap\n" \
asm (".globl _hurd_intr_rpc_msg_about_to\n" \
".globl _hurd_intr_rpc_msg_cx_sp\n" \
".globl _hurd_intr_rpc_msg_do_trap\n" \
".globl _hurd_intr_rpc_msg_in_trap\n" \
".globl _hurd_intr_rpc_msg_sp_restored\n" \
" movl %%esp, %%ecx\n" \
" leal %3, %%esp\n" \
"_hurd_intr_rpc_msg_about_to: cmpl $0, %5\n" \
" jz _hurd_intr_rpc_msg_do\n" \
" movl $0, %3\n" \
" movl %6, %%eax\n" \
" jmp _hurd_intr_rpc_msg_sp_restored\n" \
"_hurd_intr_rpc_msg_do: movl %%esp, %%ecx\n" \
" leal %4, %%esp\n" \
"_hurd_intr_rpc_msg_cx_sp: movl $-25, %%eax\n" \
"_hurd_intr_rpc_msg_do_trap: lcall $7, $0 # status in %0\n" \
"_hurd_intr_rpc_msg_in_trap: movl %%ecx, %%esp\n" \
"_hurd_intr_rpc_msg_sp_restored:" \
: "=a" (err), "+m" (option), "+m" (timeout) \
: "m" ((&msg)[-1]) \
: "=a" (err), "+m" (option), "+m" (timeout), "=m" (*intr_port_p) \
: "m" ((&msg)[-1]), "m" (*cancel_p), "i" (EINTR) \
: "ecx"); \
err; \
})