Make palloc_array() and friends safe against integer overflow.

Sufficiently large "count" arguments could result in undetected
overflow, causing the allocated memory chunk to be much smaller
than what the caller will subsequently write into it.  This is
unlikely to be a hazard with 64-bit size_t but can sometimes
happen on 32-bit builds, primarily where a function allocates
workspace that's significantly larger than its input data.
Rather than trying to patch the at-risk callers piecemeal,
let's just redefine these macros so that they always check.

To do that, move the longstanding add_size() and mul_size() functions
into palloc.h and mcxt.c, and adjust them to not be specific to
shared-memory allocation.  Then invent palloc_mul(), palloc0_mul(),
palloc_mul_extended() to use these functions.  Actually, the latter
use inlined copies to save one function call.  repalloc_array() gets
similar treatment.  I didn't bother trying to inline the calls for
repalloc0_array() though.

In v14 and v15, this also adds repalloc_extended(), which previously
was only available in v16 and up.

We need copies of all this in fe_memutils.[hc] as well, since that
module also provides palloc_array() etc.

Reported-by: Xint Code
Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Backpatch-through: 14
Security: CVE-2026-6473

diff --git a/src/backend/storage/ipc/shmem.c b/src/backend/storage/ipc/shmem.c
index 21e12e2f527ae8d65fab247cb14cc2c0926d096a..df48d1f78e98839b6d540593ea3394ab18a5abe5 100644 (file)
--- a/src/backend/storage/ipc/shmem.c
+++ b/src/backend/storage/ipc/shmem.c
@@ -486,42 +486,6 @@ ShmemInitStruct(const char *name, Size size, bool *foundPtr)
 }
 
 
-/*
- * Add two Size values, checking for overflow
- */
-Size
-add_size(Size s1, Size s2)
-{
-       Size            result;
-
-       result = s1 + s2;
-       /* We are assuming Size is an unsigned type here... */
-       if (result < s1 || result < s2)
-               ereport(ERROR,
-                               (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
-                                errmsg("requested shared memory size overflows size_t")));
-       return result;
-}
-
-/*
- * Multiply two Size values, checking for overflow
- */
-Size
-mul_size(Size s1, Size s2)
-{
-       Size            result;
-
-       if (s1 == 0 || s2 == 0)
-               return 0;
-       result = s1 * s2;
-       /* We are assuming Size is an unsigned type here... */
-       if (result / s2 != s1)
-               ereport(ERROR,
-                               (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
-                                errmsg("requested shared memory size overflows size_t")));
-       return result;
-}
-
 /* SQL SRF showing allocated shared memory */
 Datum
 pg_get_shmem_allocations(PG_FUNCTION_ARGS)

diff --git a/src/backend/utils/mmgr/mcxt.c b/src/backend/utils/mmgr/mcxt.c
index f7689ea6de848dacb1e213ed9cbfc7bd5ce9e9db..85ee9ad90296a2de82ce13722e5f818611f51d74 100644 (file)
--- a/src/backend/utils/mmgr/mcxt.c
+++ b/src/backend/utils/mmgr/mcxt.c
@@ -21,6 +21,7 @@
 
 #include "postgres.h"
 
+#include "common/int.h"
 #include "mb/pg_wchar.h"
 #include "miscadmin.h"
 #include "utils/memdebug.h"
@@ -169,6 +170,8 @@ static void MemoryContextStatsInternal(MemoryContext context, int level,
 static void MemoryContextStatsPrint(MemoryContext context, void *passthru,
                                                                        const char *stats_string,
                                                                        bool print_to_stderr);
+pg_noreturn static pg_noinline void add_size_error(Size s1, Size s2);
+pg_noreturn static pg_noinline void mul_size_error(Size s1, Size s2);
 
 /*
  * You should not do memory allocations within a critical section, because
@@ -1659,6 +1662,132 @@ repalloc0(void *pointer, Size oldsize, Size size)
        return ret;
 }
 
+/*
+ * Support for safe calculation of memory request sizes
+ *
+ * These functions perform the requested calculation, but throw error if the
+ * result overflows.
+ *
+ * An important property of these functions is that if an argument was a
+ * negative signed int before promotion (implying overflow in calculating it)
+ * we will detect that as an error.  That happens because we reject results
+ * larger than SIZE_MAX / 2 later on, in the actual allocation step.
+ */
+Size
+add_size(Size s1, Size s2)
+{
+       Size            result;
+
+       if (unlikely(pg_add_size_overflow(s1, s2, &result)))
+               add_size_error(s1, s2);
+       return result;
+}
+
+pg_noreturn static pg_noinline void
+add_size_error(Size s1, Size s2)
+{
+       ereport(ERROR,
+                       (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+                        errmsg("invalid memory allocation request size %zu + %zu",
+                                       s1, s2)));
+}
+
+Size
+mul_size(Size s1, Size s2)
+{
+       Size            result;
+
+       if (unlikely(pg_mul_size_overflow(s1, s2, &result)))
+               mul_size_error(s1, s2);
+       return result;
+}
+
+pg_noreturn static pg_noinline void
+mul_size_error(Size s1, Size s2)
+{
+       ereport(ERROR,
+                       (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+                        errmsg("invalid memory allocation request size %zu * %zu",
+                                       s1, s2)));
+}
+
+/*
+ * palloc_mul
+ *             Equivalent to palloc(mul_size(s1, s2)).
+ */
+void *
+palloc_mul(Size s1, Size s2)
+{
+       /* inline mul_size() for efficiency */
+       Size            req;
+
+       if (unlikely(pg_mul_size_overflow(s1, s2, &req)))
+               mul_size_error(s1, s2);
+       return palloc(req);
+}
+
+/*
+ * palloc0_mul
+ *             Equivalent to palloc0(mul_size(s1, s2)).
+ *
+ * This is comparable to standard calloc's behavior.
+ */
+void *
+palloc0_mul(Size s1, Size s2)
+{
+       /* inline mul_size() for efficiency */
+       Size            req;
+
+       if (unlikely(pg_mul_size_overflow(s1, s2, &req)))
+               mul_size_error(s1, s2);
+       return palloc0(req);
+}
+
+/*
+ * palloc_mul_extended
+ *             Equivalent to palloc_extended(mul_size(s1, s2), flags).
+ */
+void *
+palloc_mul_extended(Size s1, Size s2, int flags)
+{
+       /* inline mul_size() for efficiency */
+       Size            req;
+
+       if (unlikely(pg_mul_size_overflow(s1, s2, &req)))
+               mul_size_error(s1, s2);
+       return palloc_extended(req, flags);
+}
+
+/*
+ * repalloc_mul
+ *             Equivalent to repalloc(p, mul_size(s1, s2)).
+ */
+void *
+repalloc_mul(void *p, Size s1, Size s2)
+{
+       /* inline mul_size() for efficiency */
+       Size            req;
+
+       if (unlikely(pg_mul_size_overflow(s1, s2, &req)))
+               mul_size_error(s1, s2);
+       return repalloc(p, req);
+}
+
+/*
+ * repalloc_mul_extended
+ *             Equivalent to repalloc_extended(p, mul_size(s1, s2), flags).
+ */
+void *
+repalloc_mul_extended(void *p, Size s1, Size s2, int flags)
+{
+       /* inline mul_size() for efficiency */
+       Size            req;
+
+       if (unlikely(pg_mul_size_overflow(s1, s2, &req)))
+               mul_size_error(s1, s2);
+       return repalloc_extended(p, req, flags);
+}
+
 /*
  * MemoryContextAllocHuge
  *             Allocate (possibly-expansive) space within the specified context.

diff --git a/src/common/fe_memutils.c b/src/common/fe_memutils.c
index 4ba793a6132bb26353887471c009c3eccb9a0e87..f2f073c5caff30c33ca838eaa1205f36ce51efb0 100644 (file)
--- a/src/common/fe_memutils.c
+++ b/src/common/fe_memutils.c
@@ -19,6 +19,12 @@
 
 #include "postgres_fe.h"
 
+#include "common/int.h"
+
+pg_noreturn static pg_noinline void add_size_error(Size s1, Size s2);
+pg_noreturn static pg_noinline void mul_size_error(Size s1, Size s2);
+
+
 static inline void *
 pg_malloc_internal(size_t size, int flags)
 {
@@ -173,3 +179,185 @@ repalloc(void *pointer, Size size)
 {
        return pg_realloc(pointer, size);
 }
+
+/*
+ * Support for safe calculation of memory request sizes
+ *
+ * These functions perform the requested calculation, but throw error if the
+ * result overflows.
+ *
+ * An important property of these functions is that if an argument was a
+ * negative signed int before promotion (implying overflow in calculating it)
+ * we will detect that as an error.  That happens because we reject results
+ * larger than SIZE_MAX / 2.  In the backend we rely on later checks to do
+ * that, but in frontend we must do it here.
+ */
+Size
+add_size(Size s1, Size s2)
+{
+       Size            result;
+
+       if (unlikely(pg_add_size_overflow(s1, s2, &result) ||
+                                result > (SIZE_MAX / 2)))
+               add_size_error(s1, s2);
+       return result;
+}
+
+pg_noreturn static pg_noinline void
+add_size_error(Size s1, Size s2)
+{
+       fprintf(stderr, _("invalid memory allocation request size %zu + %zu\n"),
+                       s1, s2);
+       exit(EXIT_FAILURE);
+}
+
+Size
+mul_size(Size s1, Size s2)
+{
+       Size            result;
+
+       if (unlikely(pg_mul_size_overflow(s1, s2, &result) ||
+                                result > (SIZE_MAX / 2)))
+               mul_size_error(s1, s2);
+       return result;
+}
+
+pg_noreturn static pg_noinline void
+mul_size_error(Size s1, Size s2)
+{
+       fprintf(stderr, _("invalid memory allocation request size %zu * %zu\n"),
+                       s1, s2);
+       exit(EXIT_FAILURE);
+}
+
+/*
+ * pg_malloc_mul
+ *             Equivalent to pg_malloc(mul_size(s1, s2)).
+ */
+void *
+pg_malloc_mul(Size s1, Size s2)
+{
+       /* inline mul_size() for efficiency */
+       Size            req;
+
+       if (unlikely(pg_mul_size_overflow(s1, s2, &req) ||
+                                req > (SIZE_MAX / 2)))
+               mul_size_error(s1, s2);
+       return pg_malloc(req);
+}
+
+/*
+ * pg_malloc0_mul
+ *             Equivalent to pg_malloc0(mul_size(s1, s2)).
+ *
+ * This is comparable to standard calloc's behavior.
+ */
+void *
+pg_malloc0_mul(Size s1, Size s2)
+{
+       /* inline mul_size() for efficiency */
+       Size            req;
+
+       if (unlikely(pg_mul_size_overflow(s1, s2, &req) ||
+                                req > (SIZE_MAX / 2)))
+               mul_size_error(s1, s2);
+       return pg_malloc0(req);
+}
+
+/*
+ * pg_malloc_mul_extended
+ *             Equivalent to pg_malloc_extended(mul_size(s1, s2), flags).
+ */
+void *
+pg_malloc_mul_extended(Size s1, Size s2, int flags)
+{
+       /* inline mul_size() for efficiency */
+       Size            req;
+
+       if (unlikely(pg_mul_size_overflow(s1, s2, &req) ||
+                                req > (SIZE_MAX / 2)))
+               mul_size_error(s1, s2);
+       return pg_malloc_extended(req, flags);
+}
+
+/*
+ * pg_realloc_mul
+ *             Equivalent to pg_realloc(p, mul_size(s1, s2)).
+ */
+void *
+pg_realloc_mul(void *p, Size s1, Size s2)
+{
+       /* inline mul_size() for efficiency */
+       Size            req;
+
+       if (unlikely(pg_mul_size_overflow(s1, s2, &req) ||
+                                req > (SIZE_MAX / 2)))
+               mul_size_error(s1, s2);
+       return pg_realloc(p, req);
+}
+
+/*
+ * palloc_mul
+ *             Equivalent to palloc(mul_size(s1, s2)).
+ */
+void *
+palloc_mul(Size s1, Size s2)
+{
+       /* inline mul_size() for efficiency */
+       Size            req;
+
+       if (unlikely(pg_mul_size_overflow(s1, s2, &req) ||
+                                req > (SIZE_MAX / 2)))
+               mul_size_error(s1, s2);
+       return palloc(req);
+}
+
+/*
+ * palloc0_mul
+ *             Equivalent to palloc0(mul_size(s1, s2)).
+ *
+ * This is comparable to standard calloc's behavior.
+ */
+void *
+palloc0_mul(Size s1, Size s2)
+{
+       /* inline mul_size() for efficiency */
+       Size            req;
+
+       if (unlikely(pg_mul_size_overflow(s1, s2, &req) ||
+                                req > (SIZE_MAX / 2)))
+               mul_size_error(s1, s2);
+       return palloc0(req);
+}
+
+/*
+ * palloc_mul_extended
+ *             Equivalent to palloc_extended(mul_size(s1, s2), flags).
+ */
+void *
+palloc_mul_extended(Size s1, Size s2, int flags)
+{
+       /* inline mul_size() for efficiency */
+       Size            req;
+
+       if (unlikely(pg_mul_size_overflow(s1, s2, &req) ||
+                                req > (SIZE_MAX / 2)))
+               mul_size_error(s1, s2);
+       return palloc_extended(req, flags);
+}
+
+/*
+ * repalloc_mul
+ *             Equivalent to repalloc(p, mul_size(s1, s2)).
+ */
+void *
+repalloc_mul(void *p, Size s1, Size s2)
+{
+       /* inline mul_size() for efficiency */
+       Size            req;
+
+       if (unlikely(pg_mul_size_overflow(s1, s2, &req) ||
+                                req > (SIZE_MAX / 2)))
+               mul_size_error(s1, s2);
+       return repalloc(p, req);
+}

diff --git a/src/include/common/fe_memutils.h b/src/include/common/fe_memutils.h
index cd2052878618e758e55872773f4a6d654ab5144d..0ca134499e1de1b8a54fb4659fe5f4597707f657 100644 (file)
--- a/src/include/common/fe_memutils.h
+++ b/src/include/common/fe_memutils.h
@@ -41,6 +41,16 @@ extern void *pg_malloc_extended(size_t size, int flags);
 extern void *pg_realloc(void *ptr, size_t size);
 extern void pg_free(void *ptr);
 
+/*
+ * Support for safe calculation of memory request sizes
+ */
+extern Size add_size(Size s1, Size s2);
+extern Size mul_size(Size s1, Size s2);
+extern void *pg_malloc_mul(Size s1, Size s2);
+extern void *pg_malloc0_mul(Size s1, Size s2);
+extern void *pg_malloc_mul_extended(Size s1, Size s2, int flags);
+extern void *pg_realloc_mul(void *p, Size s1, Size s2);
+
 /*
  * Variants with easier notation and more type safety
  */
@@ -54,14 +64,15 @@ extern void pg_free(void *ptr);
 /*
  * Allocate space for "count" objects of type "type"
  */
-#define pg_malloc_array(type, count) ((type *) pg_malloc(sizeof(type) * (count)))
-#define pg_malloc0_array(type, count) ((type *) pg_malloc0(sizeof(type) * (count)))
+#define pg_malloc_array(type, count) ((type *) pg_malloc_mul(sizeof(type), count))
+#define pg_malloc0_array(type, count) ((type *) pg_malloc0_mul(sizeof(type), count))
+#define pg_malloc_array_extended(type, count, flags) ((type *) pg_malloc_mul_extended(sizeof(type), count, flags))
 
 /*
  * Change size of allocation pointed to by "pointer" to have space for "count"
  * objects of type "type"
  */
-#define pg_realloc_array(pointer, type, count) ((type *) pg_realloc(pointer, sizeof(type) * (count)))
+#define pg_realloc_array(pointer, type, count) ((type *) pg_realloc_mul(pointer, sizeof(type), count))
 
 /* Equivalent functions, deliberately named the same as backend functions */
 extern char *pstrdup(const char *in);
@@ -71,12 +82,17 @@ extern void *palloc0(Size size);
 extern void *palloc_extended(Size size, int flags);
 extern void *repalloc(void *pointer, Size size);
 extern void pfree(void *pointer);
+extern void *palloc_mul(Size s1, Size s2);
+extern void *palloc0_mul(Size s1, Size s2);
+extern void *palloc_mul_extended(Size s1, Size s2, int flags);
+extern void *repalloc_mul(void *p, Size s1, Size s2);
 
 #define palloc_object(type) ((type *) palloc(sizeof(type)))
 #define palloc0_object(type) ((type *) palloc0(sizeof(type)))
-#define palloc_array(type, count) ((type *) palloc(sizeof(type) * (count)))
-#define palloc0_array(type, count) ((type *) palloc0(sizeof(type) * (count)))
-#define repalloc_array(pointer, type, count) ((type *) repalloc(pointer, sizeof(type) * (count)))
+#define palloc_array(type, count) ((type *) palloc_mul(sizeof(type), count))
+#define palloc0_array(type, count) ((type *) palloc0_mul(sizeof(type), count))
+#define palloc_array_extended(type, count, flags) ((type *) palloc_mul_extended(sizeof(type), count, flags))
+#define repalloc_array(pointer, type, count) ((type *) repalloc_mul(pointer, sizeof(type), count))
 
 /* sprintf into a palloc'd buffer --- these are in psprintf.c */
 extern char *psprintf(const char *fmt,...) pg_attribute_printf(1, 2);

diff --git a/src/include/storage/shmem.h b/src/include/storage/shmem.h
index c1f668ded95235580e748e05e76e2069b276ae23..bcf7d9ea36cceccb4d46a154146e4a164c8febc0 100644 (file)
--- a/src/include/storage/shmem.h
+++ b/src/include/storage/shmem.h
@@ -38,8 +38,6 @@ extern void InitShmemIndex(void);
 extern HTAB *ShmemInitHash(const char *name, long init_size, long max_size,
                                                   HASHCTL *infoP, int hash_flags);
 extern void *ShmemInitStruct(const char *name, Size size, bool *foundPtr);
-extern Size add_size(Size s1, Size s2);
-extern Size mul_size(Size s1, Size s2);
 
 extern PGDLLIMPORT Size pg_get_shmem_pagesize(void);
 

diff --git a/src/include/utils/memutils.h b/src/include/utils/memutils.h
index 8abc26abce272a2b07dcf7cd507ee41f76e1b5a1..1375683fb8e60e4a9e753233250efab2985479e5 100644 (file)
--- a/src/include/utils/memutils.h
+++ b/src/include/utils/memutils.h
@@ -41,7 +41,7 @@
 
 #define AllocSizeIsValid(size) ((Size) (size) <= MaxAllocSize)
 
-/* Must be less than SIZE_MAX */
+/* Do not make this any bigger; see add_size() and mul_size() */
 #define MaxAllocHugeSize       (SIZE_MAX / 2)
 
 #define InvalidAllocSize       SIZE_MAX

diff --git a/src/include/utils/palloc.h b/src/include/utils/palloc.h
index e1b42267b22aa45639949d9e7af0abcf249cbf3a..e5d3f0947f4a8ed5a996009c315f8c83c4171d45 100644 (file)
--- a/src/include/utils/palloc.h
+++ b/src/include/utils/palloc.h
@@ -85,6 +85,18 @@ pg_nodiscard extern void *repalloc_extended(void *pointer,
 pg_nodiscard extern void *repalloc0(void *pointer, Size oldsize, Size size);
 extern void pfree(void *pointer);
 
+/*
+ * Support for safe calculation of memory request sizes
+ */
+extern Size add_size(Size s1, Size s2);
+extern Size mul_size(Size s1, Size s2);
+extern void *palloc_mul(Size s1, Size s2);
+extern void *palloc0_mul(Size s1, Size s2);
+extern void *palloc_mul_extended(Size s1, Size s2, int flags);
+pg_nodiscard extern void *repalloc_mul(void *p, Size s1, Size s2);
+pg_nodiscard extern void *repalloc_mul_extended(void *p, Size s1, Size s2,
+                                                                                               int flags);
+
 /*
  * Variants with easier notation and more type safety
  */
@@ -98,15 +110,17 @@ extern void pfree(void *pointer);
 /*
  * Allocate space for "count" objects of type "type"
  */
-#define palloc_array(type, count) ((type *) palloc(sizeof(type) * (count)))
-#define palloc0_array(type, count) ((type *) palloc0(sizeof(type) * (count)))
+#define palloc_array(type, count) ((type *) palloc_mul(sizeof(type), count))
+#define palloc0_array(type, count) ((type *) palloc0_mul(sizeof(type), count))
+#define palloc_array_extended(type, count, flags) ((type *) palloc_mul_extended(sizeof(type), count, flags))
 
 /*
  * Change size of allocation pointed to by "pointer" to have space for "count"
  * objects of type "type"
  */
-#define repalloc_array(pointer, type, count) ((type *) repalloc(pointer, sizeof(type) * (count)))
-#define repalloc0_array(pointer, type, oldcount, count) ((type *) repalloc0(pointer, sizeof(type) * (oldcount), sizeof(type) * (count)))
+#define repalloc_array(pointer, type, count) ((type *) repalloc_mul(pointer, sizeof(type), count))
+#define repalloc0_array(pointer, type, oldcount, count) ((type *) repalloc0(pointer, mul_size(sizeof(type), oldcount), mul_size(sizeof(type), count)))
+#define repalloc_array_extended(pointer, type, count, flags) ((type *) repalloc_mul_extended(pointer, sizeof(type), count, flags))
 
 /* Higher-limit allocators. */
 extern void *MemoryContextAllocHuge(MemoryContext context, Size size);