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Commitef29bb1

Browse files
committed
Do stack-depth checking in all postmaster children.
We used to only initialize the stack base pointer when starting up a regularbackend, not in other processes. In particular, autovacuum workers can runarbitrary user code, and without stack-depth checking, infinite recursionin 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 thecode 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 bechanged to use the function, because PL/Java is currently oblivious to theregister stack used on Itanium. There's another issues with PL/Java, namelythat the stack base pointer it sets is not really the base of the stack, itcould be something close to the bottom of the stack. That's a separate issuethat might need some further changes to this code, but that's a differentstory.Backpatch to all supported releases.
1 parent63d8636 commitef29bb1

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3 files changed

+76
-8
lines changed

3 files changed

+76
-8
lines changed

‎src/backend/postmaster/postmaster.c

Lines changed: 10 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -970,6 +970,11 @@ PostmasterMain(int argc, char *argv[])
970970
*/
971971
set_max_safe_fds();
972972

973+
/*
974+
* Set reference point for stack-depth checking.
975+
*/
976+
set_stack_base();
977+
973978
/*
974979
* Initialize the list of active backends.
975980
*/
@@ -3990,6 +3995,11 @@ SubPostmasterMain(int argc, char *argv[])
39903995
memset(&port,0,sizeof(Port));
39913996
read_backend_variables(argv[2],&port);
39923997

3998+
/*
3999+
* Set reference point for stack-depth checking
4000+
*/
4001+
set_stack_base();
4002+
39934003
/*
39944004
* Set up memory area for GSS information. Mirrors the code in ConnCreate
39954005
* for the non-exec case.

‎src/backend/tcop/postgres.c

Lines changed: 53 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -114,8 +114,10 @@ intPostAuthDelay = 0;
114114
staticlongmax_stack_depth_bytes=100*1024L;
115115

116116
/*
117-
* Stack base pointer -- initialized by PostgresMain. This is not static
118-
* so that PL/Java can modify it.
117+
* Stack base pointer -- initialized by PostmasterMain and inherited by
118+
* subprocesses. This is not static because old versions of PL/Java modify
119+
* it directly. Newer versions use set_stack_base(), but we want to stay
120+
* binary-compatible for the time being.
119121
*/
120122
char*stack_base_ptr=NULL;
121123

@@ -3002,6 +3004,53 @@ ia64_get_bsp(void)
30023004
#endif/* IA64 */
30033005

30043006

3007+
/*
3008+
* set_stack_base: set up reference point for stack depth checking
3009+
*
3010+
* Returns the old reference point, if any.
3011+
*/
3012+
pg_stack_base_t
3013+
set_stack_base(void)
3014+
{
3015+
charstack_base;
3016+
pg_stack_base_told;
3017+
3018+
#if defined(__ia64__)|| defined(__ia64)
3019+
old.stack_base_ptr=stack_base_ptr;
3020+
old.register_stack_base_ptr=register_stack_base_ptr;
3021+
#else
3022+
old=stack_base_ptr;
3023+
#endif
3024+
3025+
/* Set up reference point for stack depth checking */
3026+
stack_base_ptr=&stack_base;
3027+
#if defined(__ia64__)|| defined(__ia64)
3028+
register_stack_base_ptr=ia64_get_bsp();
3029+
#endif
3030+
3031+
returnold;
3032+
}
3033+
3034+
/*
3035+
* restore_stack_base: restore reference point for stack depth checking
3036+
*
3037+
* This can be used after set_stack_base() to restore the old value. This
3038+
* is currently only used in PL/Java. When PL/Java calls a backend function
3039+
* from different thread, the thread's stack is at a different location than
3040+
* the main thread's stack, so it sets the base pointer before the call, and
3041+
* restores it afterwards.
3042+
*/
3043+
void
3044+
restore_stack_base(pg_stack_base_tbase)
3045+
{
3046+
#if defined(__ia64__)|| defined(__ia64)
3047+
stack_base_ptr=base.stack_base_ptr;
3048+
register_stack_base_ptr=base.register_stack_base_ptr;
3049+
#else
3050+
stack_base_ptr=base;
3051+
#endif
3052+
}
3053+
30053054
/*
30063055
* check_stack_depth: check for excessively deep recursion
30073056
*
@@ -3017,7 +3066,7 @@ check_stack_depth(void)
30173066
longstack_depth;
30183067

30193068
/*
3020-
* Compute distance fromPostgresMain's local variables to myown
3069+
* Compute distance fromreference point to to mylocal variables
30213070
*/
30223071
stack_depth= (long) (stack_base_ptr-&stack_top_loc);
30233072

@@ -3459,7 +3508,6 @@ PostgresMain(int argc, char *argv[], const char *username)
34593508
{
34603509
constchar*dbname;
34613510
intfirstchar;
3462-
charstack_base;
34633511
StringInfoDatainput_message;
34643512
sigjmp_buflocal_sigjmp_buf;
34653513
volatileboolsend_ready_for_query= true;
@@ -3486,10 +3534,7 @@ PostgresMain(int argc, char *argv[], const char *username)
34863534
SetProcessingMode(InitProcessing);
34873535

34883536
/* Set up reference point for stack depth checking */
3489-
stack_base_ptr=&stack_base;
3490-
#if defined(__ia64__)|| defined(__ia64)
3491-
register_stack_base_ptr=ia64_get_bsp();
3492-
#endif
3537+
set_stack_base();
34933538

34943539
/* Compute paths, if we didn't inherit them from postmaster */
34953540
if (my_exec_path[0]=='\0')

‎src/include/miscadmin.h

Lines changed: 13 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -235,6 +235,19 @@ extern bool VacuumCostActive;
235235

236236

237237
/* in tcop/postgres.c */
238+
239+
#if defined(__ia64__)|| defined(__ia64)
240+
typedefstruct
241+
{
242+
char*stack_base_ptr;
243+
char*register_stack_base_ptr;
244+
}pg_stack_base_t;
245+
#else
246+
typedefchar*pg_stack_base_t;
247+
#endif
248+
249+
externpg_stack_base_tset_stack_base(void);
250+
externvoidrestore_stack_base(pg_stack_base_tbase);
238251
externvoidcheck_stack_depth(void);
239252

240253
/* in tcop/utility.c */

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