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fusefs: fix another semi-infinite loop bug regarding signal handling

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fticket_wait_answer would spin if it received an unhandled signal whose
default disposition is to terminate.  The reason is because msleep(9) would
return EINTR even for a masked signal.  One reason is when the thread is
stopped, which happens for example during sigexit().  Fix this bug by
returning immediately if fticket_wait_answer ever gets interrupted a second
time, for any reason.

Sponsored by:	The FreeBSD Foundation
This commit is contained in:
Alan Somers 2019-07-18 15:30:00 +00:00
parent d26d63a4af
commit f05962453e
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/projects/fuse2/; revision=350113
1 changed files with 14 additions and 8 deletions
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22
sys/fs/fuse/fuse_ipc.c
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@ -439,11 +439,12 @@ fticket_wait_answer(struct fuse_ticket *ftick)
sigset_t blockedset, oldset;
int err = 0, stops_deferred;
struct fuse_data *data;
bool interrupted = false;
if (fsess_isimpl(ftick->tk_data->mp, FUSE_INTERRUPT)) {
SIGEMPTYSET(blockedset);
} else {
/* May as well block all signals */
/* Block all signals except (implicitly) SIGKILL */
SIGFILLSET(blockedset);
}
stops_deferred = sigdeferstop(SIGDEFERSTOP_SILENT);
@ -489,7 +490,6 @@ fticket_wait_answer(struct fuse_ticket *ftick)
* or EAGAIN to the interrupt.
*/
sigset_t tmpset;
int sig;
SDT_PROBE2(fusefs, , ipc, trace, 4,
"fticket_wait_answer: interrupt");
@ -498,22 +498,28 @@ fticket_wait_answer(struct fuse_ticket *ftick)
PROC_LOCK(td->td_proc);
mtx_lock(&td->td_proc->p_sigacts->ps_mtx);
sig = cursig(td);
tmpset = td->td_proc->p_siglist;
SIGSETOR(tmpset, td->td_siglist);
mtx_unlock(&td->td_proc->p_sigacts->ps_mtx);
PROC_UNLOCK(td->td_proc);
fuse_lck_mtx_lock(ftick->tk_aw_mtx);
if (!SIGISMEMBER(tmpset, SIGKILL)) {
if (!interrupted && !SIGISMEMBER(tmpset, SIGKILL)) {
/*
* Block the just-delivered signal while we wait for an
* interrupt response
* Block all signals while we wait for an interrupt
* response. The protocol doesn't discriminate between
* different signals.
*/
SIGADDSET(blockedset, sig);
SIGFILLSET(blockedset);
interrupted = true;
goto retry;
} else {
/* Return immediately for fatal signals */
/*
* Return immediately for fatal signals, or if this is
* the second interruption. We should only be
* interrupted twice if the thread is stopped, for
* example during sigexit.
*/
}
} else if (err) {
SDT_PROBE2(fusefs, , ipc, trace, 6,