lib/glibc
1
0
Fork 0
mirror of https://sourceware.org/git/glibc.git synced 2025-07-28 00:21:52 +03:00
Code Activity

Fix races in setXid implementation.

Browse Source
This commit is contained in:
Daniel Jacobowitz
2009-10-30 01:00:44 -07:00
committed by Ulrich Drepper
parent 31c759bf37
commit 25db0f6ca9
3 changed files with 125 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files

127
nptl/allocatestack.c
View File

@ -965,22 +965,53 @@ __find_thread_by_id (pid_t tid)
static void
internal_function
setxid_mark_thread (struct xid_command *cmdp, struct pthread *t)
{
int ch;
/* Don't let the thread exit before the setxid handler runs. */
t->setxid_futex = 0;
do
{
ch = t->cancelhandling;
/* If the thread is exiting right now, ignore it. */
if ((ch & EXITING_BITMASK) != 0)
return;
}
while (atomic_compare_and_exchange_bool_acq (&t->cancelhandling,
ch | SETXID_BITMASK, ch));
}
static void
internal_function
setxid_unmark_thread (struct xid_command *cmdp, struct pthread *t)
{
int ch;
do
{
ch = t->cancelhandling;
if ((ch & SETXID_BITMASK) == 0)
return;
}
while (atomic_compare_and_exchange_bool_acq (&t->cancelhandling,
ch & ~SETXID_BITMASK, ch));
/* Release the futex just in case. */
t->setxid_futex = 1;
lll_futex_wake (&t->setxid_futex, 1, LLL_PRIVATE);
}
static int
internal_function
setxid_signal_thread (struct xid_command *cmdp, struct pthread *t)
{
if (! IS_DETACHED (t))
{
int ch;
do
{
ch = t->cancelhandling;
/* If the thread is exiting right now, ignore it. */
if ((ch & EXITING_BITMASK) != 0)
return;
}
while (atomic_compare_and_exchange_bool_acq (&t->cancelhandling,
ch | SETXID_BITMASK, ch));
}
if ((t->cancelhandling & SETXID_BITMASK) == 0)
return 0;
int val;
INTERNAL_SYSCALL_DECL (err);
@ -997,8 +1028,14 @@ setxid_signal_thread (struct xid_command *cmdp, struct pthread *t)
val = INTERNAL_SYSCALL (tkill, err, 2, t->tid, SIGSETXID);
#endif
/* If this failed, it must have had not started yet or else exited. */
if (!INTERNAL_SYSCALL_ERROR_P (val, err))
atomic_increment (&cmdp->cntr);
{
atomic_increment (&cmdp->cntr);
return 1;
}
else
return 0;
}
@ -1006,6 +1043,7 @@ int
attribute_hidden
__nptl_setxid (struct xid_command *cmdp)
{
int signalled;
int result;
lll_lock (stack_cache_lock, LLL_PRIVATE);
@ -1022,7 +1060,7 @@ __nptl_setxid (struct xid_command *cmdp)
if (t == self)
continue;
setxid_signal_thread (cmdp, t);
setxid_mark_thread (cmdp, t);
}
/* Now the list with threads using user-allocated stacks. */
@ -1032,14 +1070,61 @@ __nptl_setxid (struct xid_command *cmdp)
if (t == self)
continue;
setxid_signal_thread (cmdp, t);
setxid_mark_thread (cmdp, t);
}
int cur = cmdp->cntr;
while (cur != 0)
/* Iterate until we don't succeed in signalling anyone. That means
we have gotten all running threads, and their children will be
automatically correct once started. */
do
{
lll_futex_wait (&cmdp->cntr, cur, LLL_PRIVATE);
cur = cmdp->cntr;
signalled = 0;
list_for_each (runp, &stack_used)
{
struct pthread *t = list_entry (runp, struct pthread, list);
if (t == self)
continue;
signalled += setxid_signal_thread (cmdp, t);
}
list_for_each (runp, &__stack_user)
{
struct pthread *t = list_entry (runp, struct pthread, list);
if (t == self)
continue;
signalled += setxid_signal_thread (cmdp, t);
}
int cur = cmdp->cntr;
while (cur != 0)
{
lll_futex_wait (&cmdp->cntr, cur, LLL_PRIVATE);
cur = cmdp->cntr;
}
}
while (signalled != 0);
/* Clean up flags, so that no thread blocks during exit waiting
for a signal which will never come. */
list_for_each (runp, &stack_used)
{
struct pthread *t = list_entry (runp, struct pthread, list);
if (t == self)
continue;
setxid_unmark_thread (cmdp, t);
}
list_for_each (runp, &__stack_user)
{
struct pthread *t = list_entry (runp, struct pthread, list);
if (t == self)
continue;
setxid_unmark_thread (cmdp, t);
}
/* This must be last, otherwise the current thread might not have