mirror of https://github.com/citusdata/citus.git
1af28b3f27
(Hopefully) Fixes #5000. If memory allocation done for `SubXactContext *state` in `PushSubXact()` fails, then `PopSubXact()` might segfault, for example, when grabbing the topmost `SubXactContext` from `activeSubXactContexts` if this is the first ever subxact within the current xact, with the following stack trace: ```c citus.so!list_nth_cell(const List * list, int n) (\opt\pgenv\pgsql-14.3\include\server\nodes\pg_list.h:260) citus.so!PopSubXact(SubTransactionId subId) (\home\onurctirtir\citus\src\backend\distributed\transaction\transaction_management.c:761) citus.so!CoordinatedSubTransactionCallback(SubXactEvent event, SubTransactionId subId, SubTransactionId parentSubid, void * arg) (\home\onurctirtir\citus\src\backend\distributed\transaction\transaction_management.c:673) CallSubXactCallbacks(SubXactEvent event, SubTransactionId mySubid, SubTransactionId parentSubid) (\opt\pgenv\src\postgresql-14.3\src\backend\access\transam\xact.c:3644) AbortSubTransaction() (\opt\pgenv\src\postgresql-14.3\src\backend\access\transam\xact.c:5058) AbortCurrentTransaction() (\opt\pgenv\src\postgresql-14.3\src\backend\access\transam\xact.c:3366) PostgresMain(int argc, char ** argv, const char * dbname, const char * username) (\opt\pgenv\src\postgresql-14.3\src\backend\tcop\postgres.c:4250) BackendRun(Port * port) (\opt\pgenv\src\postgresql-14.3\src\backend\postmaster\postmaster.c:4530) BackendStartup(Port * port) (\opt\pgenv\src\postgresql-14.3\src\backend\postmaster\postmaster.c:4252) ServerLoop() (\opt\pgenv\src\postgresql-14.3\src\backend\postmaster\postmaster.c:1745) PostmasterMain(int argc, char ** argv) (\opt\pgenv\src\postgresql-14.3\src\backend\postmaster\postmaster.c:1417) main(int argc, char ** argv) (\opt\pgenv\src\postgresql-14.3\src\backend\main\main.c:209) ``` For this reason, to be more defensive against memory-allocation errors that could happen at `PushSubXact()`, now we use our pre-allocated memory context for the objects created in `PushSubXact()`. This commit also attempts reducing the memory allocations done under CommitContext to reduce the chances of consuming all the memory available to CommitContext. Note that it's problematic to encounter with such a memory-allocation error for other objects created in `PushSubXact()` as well, so above is an **example** scenario that might result in a segfault. DESCRIPTION: Fixes a bug that might cause segfaults when handling deeply nested subtransactions |
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| .. | ||
| backend_data.c | ||
| citus_dist_stat_activity.c | ||
| distributed_deadlock_detection.c | ||
| lock_graph.c | ||
| relation_access_tracking.c | ||
| remote_transaction.c | ||
| transaction_management.c | ||
| transaction_recovery.c | ||
| worker_transaction.c | ||