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Push enable/disable of notify and catchup interrupts all the way down 

to just around the bare recv() call that gets a command from the client.
The former placement in PostgresMain was unsafe because the intermediate
processing layers (especially SSL) use facilities such as malloc that are
not necessarily re-entrant.  Per report from counterstorm.com.
This commit is contained in:
Tom Lane 2005-06-02 21:03:25 +00:00
parent 8dfb616606
commit b5ebef7c41
3 changed files with 142 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

80
src/backend/libpq/be-secure.c
View File

@ -11,7 +11,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/libpq/be-secure.c,v 1.56 2005/01/08 22:51:12 tgl Exp $
* $PostgreSQL: pgsql/src/backend/libpq/be-secure.c,v 1.57 2005/06/02 21:03:17 tgl Exp $
*
* Since the server static private key ($DataDir/server.key)
* will normally be stored unencrypted so that the database
@ -79,7 +79,6 @@
#include <sys/stat.h>
#include <signal.h>
#include <fcntl.h>
#include <errno.h>
#include <ctype.h>
#include <sys/socket.h>
#include <unistd.h>
@ -97,6 +96,8 @@
#include "libpq/libpq.h"
#include "miscadmin.h"
#include "tcop/tcopprot.h"
#ifdef USE_SSL
static DH *load_dh_file(int keylength);
@ -308,8 +309,14 @@ rloop:
}
else
#endif
{
prepare_for_client_read();
n = recv(port->sock, ptr, len, 0);
client_read_ended();
}
return n;
}
@ -410,6 +417,73 @@ wloop:
/* SSL specific code */
/* ------------------------------------------------------------ */
#ifdef USE_SSL
/*
* Private substitute BIO: this wraps the SSL library's standard socket BIO
* so that we can enable and disable interrupts just while calling recv().
* We cannot have interrupts occurring while the bulk of openssl runs,
* because it uses malloc() and possibly other non-reentrant libc facilities.
*
* As of openssl 0.9.7, we can use the reasonably clean method of interposing
* a wrapper around the standard socket BIO's sock_read() method. This relies
* on the fact that sock_read() doesn't call anything non-reentrant, in fact
* not much of anything at all except recv(). If this ever changes we'd
* probably need to duplicate the code of sock_read() in order to push the
* interrupt enable/disable down yet another level.
*/
static bool my_bio_initialized = false;
static BIO_METHOD my_bio_methods;
static int (*std_sock_read) (BIO *h, char *buf, int size);
static int
my_sock_read(BIO *h, char *buf, int size)
{
int res;
prepare_for_client_read();
res = std_sock_read(h, buf, size);
client_read_ended();
return res;
}
static BIO_METHOD *
my_BIO_s_socket(void)
{
if (!my_bio_initialized)
{
memcpy(&my_bio_methods, BIO_s_socket(), sizeof(BIO_METHOD));
std_sock_read = my_bio_methods.bread;
my_bio_methods.bread = my_sock_read;
my_bio_initialized = true;
}
return &my_bio_methods;
}
/* This should exactly match openssl's SSL_set_fd except for using my BIO */
static int
my_SSL_set_fd(SSL *s, int fd)
{
int ret=0;
BIO *bio=NULL;
bio=BIO_new(my_BIO_s_socket());
if (bio == NULL)
{
SSLerr(SSL_F_SSL_SET_FD,ERR_R_BUF_LIB);
goto err;
}
BIO_set_fd(bio,fd,BIO_NOCLOSE);
SSL_set_bio(s,bio,bio);
ret=1;
err:
return(ret);
}
/*
* Load precomputed DH parameters.
*
@ -761,7 +835,7 @@ open_server_SSL(Port *port)
close_SSL(port);
return -1;
}
if (!SSL_set_fd(port->ssl, port->sock))
if (!my_SSL_set_fd(port->ssl, port->sock))
{
ereport(COMMERROR,
(errcode(ERRCODE_PROTOCOL_VIOLATION),

82
src/backend/tcop/postgres.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.445 2005/06/01 23:27:03 momjian Exp $
* $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.446 2005/06/02 21:03:24 tgl Exp $
*
* NOTES
* this is the "main" module of the postgres backend and
@ -111,6 +111,13 @@ static volatile sig_atomic_t got_SIGHUP = false;
*/
static bool xact_started = false;
/*
* Flag to indicate that we are doing the outer loop's read-from-client,
* as opposed to any random read from client that might happen within
* commands like COPY FROM STDIN.
*/
static bool DoingCommandRead = false;
/*
* Flags to implement skip-till-Sync-after-error behavior for messages of
* the extended query protocol.
@ -406,6 +413,52 @@ ReadCommand(StringInfo inBuf)
return result;
}
/*
* prepare_for_client_read -- set up to possibly block on client input
*
* This must be called immediately before any low-level read from the
* client connection. It is necessary to do it at a sufficiently low level
* that there won't be any other operations except the read kernel call
* itself between this call and the subsequent client_read_ended() call.
* In particular there mustn't be use of malloc() or other potentially
* non-reentrant libc functions. This restriction makes it safe for us
* to allow interrupt service routines to execute nontrivial code while
* we are waiting for input.
*/
void
prepare_for_client_read(void)
{
if (DoingCommandRead)
{
/* Enable immediate processing of asynchronous signals */
EnableNotifyInterrupt();
EnableCatchupInterrupt();
/* Allow "die" interrupt to be processed while waiting */
ImmediateInterruptOK = true;
/* And don't forget to detect one that already arrived */
QueryCancelPending = false;
CHECK_FOR_INTERRUPTS();
}
}
/*
* client_read_ended -- get out of the client-input state
*/
void
client_read_ended(void)
{
if (DoingCommandRead)
{
ImmediateInterruptOK = false;
QueryCancelPending = false; /* forget any CANCEL signal */
DisableNotifyInterrupt();
DisableCatchupInterrupt();
}
}
/*
* Parse a query string and pass it through the rewriter.
@ -2959,6 +3012,7 @@ PostgresMain(int argc, char *argv[], const char *username)
* not in other exception-catching places since these interrupts
* are only enabled while we wait for client input.
*/
DoingCommandRead = false;
DisableNotifyInterrupt();
DisableCatchupInterrupt();
@ -3063,21 +3117,13 @@ PostgresMain(int argc, char *argv[], const char *username)
}
/*
* (2) deal with pending asynchronous NOTIFY from other backends,
* and enable async.c's signal handler to execute NOTIFY directly.
* Then set up other stuff needed before blocking for input.
* (2) Allow asynchronous signals to be executed immediately
* if they come in while we are waiting for client input.
* (This must be conditional since we don't want, say, reads on
* behalf of COPY FROM STDIN doing the same thing.)
*/
QueryCancelPending = false; /* forget any earlier CANCEL
* signal */
EnableNotifyInterrupt();
EnableCatchupInterrupt();
/* Allow "die" interrupt to be processed while waiting */
ImmediateInterruptOK = true;
/* and don't forget to detect one that already arrived */
QueryCancelPending = false;
CHECK_FOR_INTERRUPTS();
QueryCancelPending = false; /* forget any earlier CANCEL signal */
DoingCommandRead = true;
/*
* (3) read a command (loop blocks here)
@ -3087,11 +3133,7 @@ PostgresMain(int argc, char *argv[], const char *username)
/*
* (4) disable async signal conditions again.
*/
ImmediateInterruptOK = false;
QueryCancelPending = false; /* forget any CANCEL signal */
DisableNotifyInterrupt();
DisableCatchupInterrupt();
DoingCommandRead = false;
/*
* (5) check for any other interesting events that happened while

4
src/include/tcop/tcopprot.h
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/tcop/tcopprot.h,v 1.73 2004/12/31 22:03:44 pgsql Exp $
* $PostgreSQL: pgsql/src/include/tcop/tcopprot.h,v 1.74 2005/06/02 21:03:25 tgl Exp $
*
* OLD COMMENTS
* This file was created so that other c files could get the two
@ -59,6 +59,8 @@ extern bool assign_max_stack_depth(int newval, bool doit, GucSource source);
extern void die(SIGNAL_ARGS);
extern void quickdie(SIGNAL_ARGS);
extern void authdie(SIGNAL_ARGS);
extern void prepare_for_client_read(void);
extern void client_read_ended(void);
extern int PostgresMain(int argc, char *argv[], const char *username);
extern void ResetUsage(void);
extern void ShowUsage(const char *title);