Fix possible crashes due to using elog/ereport too early in startup.

Per reports from Andres Freund and Luke Campbell, a server failure during
set_pglocale_pgservice results in a segfault rather than a useful error
message, because the infrastructure needed to use ereport hasn't been
initialized; specifically, MemoryContextInit hasn't been called.
One known cause of this is starting the server in a directory it
doesn't have permission to read.

We could try to prevent set_pglocale_pgservice from using anything that
depends on palloc or elog, but that would be messy, and the odds of future
breakage seem high.  Moreover there are other things being called in main.c
that look likely to use palloc or elog too --- perhaps those things
shouldn't be there, but they are there today.  The best solution seems to
be to move the call of MemoryContextInit to very early in the backend's
real main() function.  I've verified that an elog or ereport occurring
immediately after that is now capable of sending something useful to
stderr.

I also added code to elog.c to print something intelligible rather than
just crashing if MemoryContextInit hasn't created the ErrorContext.
This could happen if MemoryContextInit itself fails (due to malloc
failure), and provides some future-proofing against someone trying to
sneak in new code even earlier in server startup.

Back-patch to all supported branches.  Since we've only heard reports of
this type of failure recently, it may be that some recent change has made
it more likely to see a crash of this kind; but it sure looks like it's
broken all the way back.

diff --git a/src/backend/bootstrap/bootstrap.c b/src/backend/bootstrap/bootstrap.c
index 9d1d8e37ccc07c58aa39f84122f352f49c14ea4c..cb671b4346864df24e9a334d9bfbc7fb347d8ceb 100644 (file)
--- a/src/backend/bootstrap/bootstrap.c
+++ b/src/backend/bootstrap/bootstrap.c
@@ -202,14 +202,6 @@ AuxiliaryProcessMain(int argc, char *argv[])
 
        MyStartTime = time(NULL);
 
-       /*
-        * Fire up essential subsystems: error and memory management
-        *
-        * If we are running under the postmaster, this is done already.
-        */
-       if (!IsUnderPostmaster)
-               MemoryContextInit();
-
        /* Compute paths, if we didn't inherit them from postmaster */
        if (my_exec_path[0] == '\0')
        {

diff --git a/src/backend/main/main.c b/src/backend/main/main.c
index 8ea6c1f387405a23059a021f89602d827528dfde..2421ccbdf7b5bde1472c0912960709d88edc4e7d 100644 (file)
--- a/src/backend/main/main.c
+++ b/src/backend/main/main.c
@@ -39,6 +39,7 @@
 #include "postmaster/postmaster.h"
 #include "tcop/tcopprot.h"
 #include "utils/help_config.h"
+#include "utils/memutils.h"
 #include "utils/pg_locale.h"
 #include "utils/ps_status.h"
 
@@ -86,6 +87,15 @@ main(int argc, char *argv[])
        pgwin32_install_crashdump_handler();
 #endif
 
+       /*
+        * Fire up essential subsystems: error and memory management
+        *
+        * Code after this point is allowed to use elog/ereport, though
+        * localization of messages may not work right away, and messages won't go
+        * anywhere but stderr until GUC settings get loaded.
+        */
+       MemoryContextInit();
+
        /*
         * Set up locale information from environment.  Note that LC_CTYPE and
         * LC_COLLATE will be overridden later from pg_control if we are in an

diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index ccb8b86a49fb51fc9727f1f2dde53f47e02071b6..18a68f80db7d3f65e65749a0d5a18ab4dafcffa2 100644 (file)
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -575,11 +575,6 @@ PostmasterMain(int argc, char *argv[])
         */
        umask(S_IRWXG | S_IRWXO);
 
-       /*
-        * Fire up essential subsystems: memory management
-        */
-       MemoryContextInit();
-
        /*
         * By default, palloc() requests in the postmaster will be allocated in
         * the PostmasterContext, which is space that can be recycled by backends.
@@ -4379,7 +4374,6 @@ SubPostmasterMain(int argc, char *argv[])
        whereToSendOutput = DestNone;
 
        /* Setup essential subsystems (to ensure elog() behaves sanely) */
-       MemoryContextInit();
        InitializeGUCOptions();
 
        /* Read in the variables file */

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 9c2a8edba47e89b05514507307a5c8b468f296e4..c466453a767c57c2c2bab0ebe341c3c5c18077f6 100644 (file)
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -3542,14 +3542,6 @@ PostgresMain(int argc, char *argv[],
                MyStartTime = time(NULL);
        }
 
-       /*
-        * Fire up essential subsystems: error and memory management
-        *
-        * If we are running under the postmaster, this is done already.
-        */
-       if (!IsUnderPostmaster)
-               MemoryContextInit();
-
        SetProcessingMode(InitProcessing);
 
        /* Compute paths, if we didn't inherit them from postmaster */

diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 35cb875a1236852d04f189e1ac51680bf5324981..ee40692c279d78cb6dbec2a4d58e0121842cb3be 100644 (file)
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -309,6 +309,18 @@ errstart(int elevel, const char *filename, int lineno,
        if (elevel < ERROR && !output_to_server && !output_to_client)
                return false;
 
+       /*
+        * We need to do some actual work.  Make sure that memory context
+        * initialization has finished, else we can't do anything useful.
+        */
+       if (ErrorContext == NULL)
+       {
+               /* Ooops, hard crash time; very little we can do safely here */
+               write_stderr("error occurred at %s:%d before error message processing is available\n",
+                                        filename ? filename : "(unknown file)", lineno);
+               exit(2);
+       }
+
        /*
         * Okay, crank up a stack entry to store the info in.
         */
@@ -1231,6 +1243,15 @@ elog_start(const char *filename, int lineno, const char *funcname)
 {
        ErrorData  *edata;
 
+       /* Make sure that memory context initialization has finished */
+       if (ErrorContext == NULL)
+       {
+               /* Ooops, hard crash time; very little we can do safely here */
+               write_stderr("error occurred at %s:%d before error message processing is available\n",
+                                        filename ? filename : "(unknown file)", lineno);
+               exit(2);
+       }
+
        if (++errordata_stack_depth >= ERRORDATA_STACK_SIZE)
        {
                /*

diff --git a/src/backend/utils/mmgr/mcxt.c b/src/backend/utils/mmgr/mcxt.c
index 8dd3cf488964afaa3801b7b64c4b1ac1f9fa1157..6118e12eaf839cd43a4206dbbc063774850e91e2 100644 (file)
--- a/src/backend/utils/mmgr/mcxt.c
+++ b/src/backend/utils/mmgr/mcxt.c
@@ -71,7 +71,8 @@ static void MemoryContextStatsInternal(MemoryContext context, int level);
  * In normal multi-backend operation, this is called once during
  * postmaster startup, and not at all by individual backend startup
  * (since the backends inherit an already-initialized context subsystem
- * by virtue of being forked off the postmaster).
+ * by virtue of being forked off the postmaster).  But in an EXEC_BACKEND
+ * build, each process must do this for itself.
  *
  * In a standalone backend this must be called during backend startup.
  */
@@ -105,6 +106,9 @@ MemoryContextInit(void)
         * where retained memory in a context is *essential* --- we want to be
         * sure ErrorContext still has some memory even if we've run out
         * elsewhere!
+        *
+        * This should be the last step in this function, as elog.c assumes memory
+        * management works once ErrorContext is non-null.
         */
        ErrorContext = AllocSetContextCreate(TopMemoryContext,
                                                                                 "ErrorContext",