From ef3883d130cb553003015f3da7fa59415da6f5c9 Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Sun, 8 Apr 2012 18:28:12 +0300
Subject: [PATCH] Do stack-depth checking in all postmaster children.
We used to only initialize the stack base pointer when starting up a regular
backend, not in other processes. In particular, autovacuum workers can run
arbitrary user code, and without stack-depth checking, infinite recursion
in e.g an index expression will bring down the whole cluster.
The comment about PL/Java using set_stack_base() is not yet true. As the
code stands, PL/java still modifies the stack_base_ptr variable directly.
However, it's been discussed in the PL/Java mailing list that it should be
changed to use the function, because PL/Java is currently oblivious to the
register stack used on Itanium. There's another issues with PL/Java, namely
that the stack base pointer it sets is not really the base of the stack, it
could be something close to the bottom of the stack. That's a separate issue
that might need some further changes to this code, but that's a different
story.
Backpatch to all supported releases.
---
src/backend/postmaster/postmaster.c | 10 +++++
src/backend/tcop/postgres.c | 61 +++++++++++++++++++++++++----
src/include/miscadmin.h | 13 ++++++
3 files changed, 76 insertions(+), 8 deletions(-)
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 1dac6954885..a481eef2c28 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -970,6 +970,11 @@ PostmasterMain(int argc, char *argv[])
*/
set_max_safe_fds();
+ /*
+ * Set reference point for stack-depth checking.
+ */
+ set_stack_base();
+
/*
* Initialize the list of active backends.
*/
@@ -3977,6 +3982,11 @@ SubPostmasterMain(int argc, char *argv[])
memset(&port, 0, sizeof(Port));
read_backend_variables(argv[2], &port);
+ /*
+ * Set reference point for stack-depth checking
+ */
+ set_stack_base();
+
/*
* Set up memory area for GSS information. Mirrors the code in ConnCreate
* for the non-exec case.
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 02be36362ce..999f63bffb7 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -115,8 +115,10 @@ int PostAuthDelay = 0;
static long max_stack_depth_bytes = 100 * 1024L;
/*
- * Stack base pointer -- initialized by PostgresMain. This is not static
- * so that PL/Java can modify it.
+ * Stack base pointer -- initialized by PostmasterMain and inherited by
+ * subprocesses. This is not static because old versions of PL/Java modify
+ * it directly. Newer versions use set_stack_base(), but we want to stay
+ * binary-compatible for the time being.
*/
char *stack_base_ptr = NULL;
@@ -2957,6 +2959,53 @@ ia64_get_bsp(void)
#endif /* IA64 */
+/*
+ * set_stack_base: set up reference point for stack depth checking
+ *
+ * Returns the old reference point, if any.
+ */
+pg_stack_base_t
+set_stack_base(void)
+{
+ char stack_base;
+ pg_stack_base_t old;
+
+#if defined(__ia64__) || defined(__ia64)
+ old.stack_base_ptr = stack_base_ptr;
+ old.register_stack_base_ptr = register_stack_base_ptr;
+#else
+ old = stack_base_ptr;
+#endif
+
+ /* Set up reference point for stack depth checking */
+ stack_base_ptr = &stack_base;
+#if defined(__ia64__) || defined(__ia64)
+ register_stack_base_ptr = ia64_get_bsp();
+#endif
+
+ return old;
+}
+
+/*
+ * restore_stack_base: restore reference point for stack depth checking
+ *
+ * This can be used after set_stack_base() to restore the old value. This
+ * is currently only used in PL/Java. When PL/Java calls a backend function
+ * from different thread, the thread's stack is at a different location than
+ * the main thread's stack, so it sets the base pointer before the call, and
+ * restores it afterwards.
+ */
+void
+restore_stack_base(pg_stack_base_t base)
+{
+#if defined(__ia64__) || defined(__ia64)
+ stack_base_ptr = base.stack_base_ptr;
+ register_stack_base_ptr = base.register_stack_base_ptr;
+#else
+ stack_base_ptr = base;
+#endif
+}
+
/*
* check_stack_depth: check for excessively deep recursion
*
@@ -2972,7 +3021,7 @@ check_stack_depth(void)
long stack_depth;
/*
- * Compute distance from PostgresMain's local variables to my own
+ * Compute distance from reference point to to my local variables
*/
stack_depth = (long) (stack_base_ptr - &stack_top_loc);
@@ -3434,7 +3483,6 @@ PostgresMain(int argc, char *argv[], const char *username)
{
const char *dbname;
int firstchar;
- char stack_base;
StringInfoData input_message;
sigjmp_buf local_sigjmp_buf;
volatile bool send_ready_for_query = true;
@@ -3461,10 +3509,7 @@ PostgresMain(int argc, char *argv[], const char *username)
SetProcessingMode(InitProcessing);
/* Set up reference point for stack depth checking */
- stack_base_ptr = &stack_base;
-#if defined(__ia64__) || defined(__ia64)
- register_stack_base_ptr = ia64_get_bsp();
-#endif
+ set_stack_base();
/* Compute paths, if we didn't inherit them from postmaster */
if (my_exec_path[0] == '\0')
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index 610cb5907e5..b186eed8f47 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -246,6 +246,19 @@ extern bool VacuumCostActive;
/* in tcop/postgres.c */
+
+#if defined(__ia64__) || defined(__ia64)
+typedef struct
+{
+ char *stack_base_ptr;
+ char *register_stack_base_ptr;
+} pg_stack_base_t;
+#else
+typedef char *pg_stack_base_t;
+#endif
+
+extern pg_stack_base_t set_stack_base(void);
+extern void restore_stack_base(pg_stack_base_t base);
extern void check_stack_depth(void);
/* in tcop/utility.c */
--
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