From: Andreas Schwab <schwab@suse.de>
To: libc-alpha@sourceware.org
Subject: [PATCH] Always do locking when accessing streams (bug 15142, bug 14697)
Date: Tue, 06 Jun 2023 16:11:05 +0200 [thread overview]
Message-ID: <mvmcz287kau.fsf@suse.de> (raw)
Now that abort no longer calls fflush there is no reason to avoid locking
the stdio streams anywhere. This fixes a conformance issue and potential
heap corruption during exit.
---
libio/genops.c | 43 ++++++++++---------------------------------
libio/libioP.h | 1 -
2 files changed, 10 insertions(+), 34 deletions(-)
diff --git a/libio/genops.c b/libio/genops.c
index 7131312704..fbd8dd9e75 100644
--- a/libio/genops.c
+++ b/libio/genops.c
@@ -682,7 +682,7 @@ _IO_adjust_column (unsigned start, const char *line, int count)
libc_hidden_def (_IO_adjust_column)
int
-_IO_flush_all_lockp (int do_lock)
+_IO_flush_all (void)
{
int result = 0;
FILE *fp;
@@ -695,8 +695,7 @@ _IO_flush_all_lockp (int do_lock)
for (fp = (FILE *) _IO_list_all; fp != NULL; fp = fp->_chain)
{
run_fp = fp;
- if (do_lock)
- _IO_flockfile (fp);
+ _IO_flockfile (fp);
if (((fp->_mode <= 0 && fp->_IO_write_ptr > fp->_IO_write_base)
|| (_IO_vtable_offset (fp) == 0
@@ -706,8 +705,7 @@ _IO_flush_all_lockp (int do_lock)
&& _IO_OVERFLOW (fp, EOF) == EOF)
result = EOF;
- if (do_lock)
- _IO_funlockfile (fp);
+ _IO_funlockfile (fp);
run_fp = NULL;
}
@@ -718,14 +716,6 @@ _IO_flush_all_lockp (int do_lock)
return result;
}
-
-
-int
-_IO_flush_all (void)
-{
- /* We want locking. */
- return _IO_flush_all_lockp (1);
-}
libc_hidden_def (_IO_flush_all)
void
@@ -791,6 +781,9 @@ _IO_unbuffer_all (void)
{
int legacy = 0;
+ run_fp = fp;
+ _IO_flockfile (fp);
+
#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_1)
if (__glibc_unlikely (_IO_vtable_offset (fp) != 0))
legacy = 1;
@@ -800,18 +793,6 @@ _IO_unbuffer_all (void)
/* Iff stream is un-orientated, it wasn't used. */
&& (legacy || fp->_mode != 0))
{
-#ifdef _IO_MTSAFE_IO
- int cnt;
-#define MAXTRIES 2
- for (cnt = 0; cnt < MAXTRIES; ++cnt)
- if (fp->_lock == NULL || _IO_lock_trylock (*fp->_lock) == 0)
- break;
- else
- /* Give the other thread time to finish up its use of the
- stream. */
- __sched_yield ();
-#endif
-
if (! legacy && ! dealloc_buffers && !(fp->_flags & _IO_USER_BUF))
{
fp->_flags |= _IO_USER_BUF;
@@ -825,17 +806,15 @@ _IO_unbuffer_all (void)
if (! legacy && fp->_mode > 0)
_IO_wsetb (fp, NULL, NULL, 0);
-
-#ifdef _IO_MTSAFE_IO
- if (cnt < MAXTRIES && fp->_lock != NULL)
- _IO_lock_unlock (*fp->_lock);
-#endif
}
/* Make sure that never again the wide char functions can be
used. */
if (! legacy)
fp->_mode = -1;
+
+ _IO_funlockfile (fp);
+ run_fp = NULL;
}
#ifdef _IO_MTSAFE_IO
@@ -861,9 +840,7 @@ __libio_freemem (void)
int
_IO_cleanup (void)
{
- /* We do *not* want locking. Some threads might use streams but
- that is their problem, we flush them underneath them. */
- int result = _IO_flush_all_lockp (0);
+ int result = _IO_flush_all ();
/* We currently don't have a reliable mechanism for making sure that
C++ static destructors are executed in the correct order.
diff --git a/libio/libioP.h b/libio/libioP.h
index d777553cb0..745278e076 100644
--- a/libio/libioP.h
+++ b/libio/libioP.h
@@ -537,7 +537,6 @@ extern int _IO_new_do_write (FILE *, const char *, size_t);
extern int _IO_old_do_write (FILE *, const char *, size_t);
extern int _IO_wdo_write (FILE *, const wchar_t *, size_t);
libc_hidden_proto (_IO_wdo_write)
-extern int _IO_flush_all_lockp (int);
extern int _IO_flush_all (void);
libc_hidden_proto (_IO_flush_all)
extern void _IO_flush_all_linebuffered (void);
--
2.41.0
--
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."
next reply other threads:[~2023-06-06 14:11 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-06 14:11 Andreas Schwab [this message]
-- strict thread matches above, loose matches on Subject: below --
2023-06-29 13:09 Andreas Schwab
2023-06-30 15:57 ` Florian Weimer
2023-07-03 7:34 ` Andreas Schwab
2023-07-03 7:53 ` Florian Weimer
2023-06-05 10:36 Andreas Schwab
2022-07-18 11:45 Andreas Schwab
2020-02-13 14:01 Andreas Schwab
2020-02-16 13:40 ` Florian Weimer
2020-02-17 9:19 ` Andreas Schwab
2020-02-17 9:42 ` Florian Weimer
2020-02-17 9:49 ` Andreas Schwab
2020-02-17 12:46 ` Florian Weimer
2019-12-11 9:55 Andreas Schwab
2019-11-25 14:20 Andreas Schwab
2019-11-25 15:05 ` Szabolcs Nagy
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