diff options
Diffstat (limited to 'src/backend/utils/adt/txid.c')
| -rw-r--r-- | src/backend/utils/adt/txid.c | 23 |
1 files changed, 13 insertions, 10 deletions
diff --git a/src/backend/utils/adt/txid.c b/src/backend/utils/adt/txid.c index de867561cd1..ac6ea7de33e 100644 --- a/src/backend/utils/adt/txid.c +++ b/src/backend/utils/adt/txid.c @@ -26,7 +26,9 @@ #include "funcapi.h" #include "miscadmin.h" #include "libpq/pqformat.h" +#include "postmaster/postmaster.h" #include "utils/builtins.h" +#include "utils/memutils.h" #include "utils/snapmgr.h" @@ -66,6 +68,8 @@ typedef struct #define TXID_SNAPSHOT_SIZE(nxip) \ (offsetof(TxidSnapshot, xip) + sizeof(txid) * (nxip)) +#define TXID_SNAPSHOT_MAX_NXIP \ + ((MaxAllocSize - offsetof(TxidSnapshot, xip)) / sizeof(txid)) /* * Epoch values from xact.c @@ -368,6 +372,13 @@ txid_current_snapshot(PG_FUNCTION_ARGS) load_xid_epoch(&state); + /* + * Compile-time limits on the procarray (MAX_BACKENDS processes plus + * MAX_BACKENDS prepared transactions) guarantee nxip won't be too large. + */ + StaticAssertStmt(MAX_BACKENDS * 2 <= TXID_SNAPSHOT_MAX_NXIP, + "possible overflow in txid_current_snapshot()"); + /* allocate */ nxip = cur->xcnt; size = TXID_SNAPSHOT_SIZE(nxip); @@ -445,20 +456,12 @@ txid_snapshot_recv(PG_FUNCTION_ARGS) txid last = 0; int nxip; int i; - int avail; - int expect; txid xmin, xmax; - /* - * load nxip and check for nonsense. - * - * (nxip > avail) check is against int overflows in 'expect'. - */ + /* load and validate nxip */ nxip = pq_getmsgint(buf, 4); - avail = buf->len - buf->cursor; - expect = 8 + 8 + nxip * 8; - if (nxip < 0 || nxip > avail || expect > avail) + if (nxip < 0 || nxip > TXID_SNAPSHOT_MAX_NXIP) goto bad_format; xmin = pq_getmsgint64(buf); |