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commit 0c19bf42f7bfcffa39fb2cd3ff7c704ce26eb3e7
Author: Tom Lane <[email protected]>
AuthorDate: Mon Nov 6 10:56:43 2023 -0500

    Detect integer overflow while computing new array dimensions.
    
    array_set_element() and related functions allow an array to be
    enlarged by assigning to subscripts outside the current array bounds.
    While these places were careful to check that the new bounds are
    allowable, they neglected to consider the risk of integer overflow
    in computing the new bounds.  In edge cases, we could compute new
    bounds that are invalid but get past the subsequent checks,
    allowing bad things to happen.  Memory stomps that are potentially
    exploitable for arbitrary code execution are possible, and so is
    disclosure of server memory.
    
    To fix, perform the hazardous computations using overflow-detecting
    arithmetic routines, which fortunately exist in all still-supported
    branches.
    
    The test cases added for this generate (after patching) errors that
    mention the value of MaxArraySize, which is platform-dependent.
    Rather than introduce multiple expected-files, use psql's VERBOSITY
    parameter to suppress the printing of the message text.  v11 psql
    lacks that parameter, so omit the tests in that branch.
    
    Our thanks to Pedro Gallegos for reporting this problem.
    
    Security: CVE-2023-5869
    (cherry picked from commit 18b585155a891784ca8985f595ebc0dde94e0d43)
---
 src/backend/utils/adt/arrayfuncs.c   | 85 ++++++++++++++++++++++++++++--------
 src/backend/utils/adt/arrayutils.c   |  6 ---
 src/include/utils/array.h            |  6 +++
 src/test/regress/expected/arrays.out | 17 ++++++++
 src/test/regress/sql/arrays.sql      | 19 ++++++++
 5 files changed, 109 insertions(+), 24 deletions(-)

diff --git a/src/backend/utils/adt/arrayfuncs.c 
b/src/backend/utils/adt/arrayfuncs.c
index 3b523d2909..26cd745896 100644
--- a/src/backend/utils/adt/arrayfuncs.c
+++ b/src/backend/utils/adt/arrayfuncs.c
@@ -19,6 +19,7 @@
 
 #include "access/htup_details.h"
 #include "catalog/pg_type.h"
+#include "common/int.h"
 #include "funcapi.h"
 #include "access/tupmacs.h"
 #include "libpq/pqformat.h"
@@ -2336,22 +2337,38 @@ array_set_element(Datum arraydatum,
        addedbefore = addedafter = 0;
 
        /*
-        * Check subscripts
+        * Check subscripts.  We assume the existing subscripts passed
+        * ArrayCheckBounds, so that dim[i] + lb[i] can be computed without
+        * overflow.  But we must beware of other overflows in our calculations 
of
+        * new dim[] values.
         */
        if (ndim == 1)
        {
                if (indx[0] < lb[0])
                {
-                       addedbefore = lb[0] - indx[0];
-                       dim[0] += addedbefore;
+                       /* addedbefore = lb[0] - indx[0]; */
+                       /* dim[0] += addedbefore; */
+                       if (pg_sub_s32_overflow(lb[0], indx[0], &addedbefore) ||
+                               pg_add_s32_overflow(dim[0], addedbefore, 
&dim[0]))
+                               ereport(ERROR,
+                                               
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+                                                errmsg("array size exceeds the 
maximum allowed (%d)",
+                                                               (int) 
MaxArraySize)));
                        lb[0] = indx[0];
                        if (addedbefore > 1)
                                newhasnulls = true; /* will insert nulls */
                }
                if (indx[0] >= (dim[0] + lb[0]))
                {
-                       addedafter = indx[0] - (dim[0] + lb[0]) + 1;
-                       dim[0] += addedafter;
+                       /* addedafter = indx[0] - (dim[0] + lb[0]) + 1; */
+                       /* dim[0] += addedafter; */
+                       if (pg_sub_s32_overflow(indx[0], dim[0] + lb[0], 
&addedafter) ||
+                               pg_add_s32_overflow(addedafter, 1, &addedafter) 
||
+                               pg_add_s32_overflow(dim[0], addedafter, 
&dim[0]))
+                               ereport(ERROR,
+                                               
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+                                                errmsg("array size exceeds the 
maximum allowed (%d)",
+                                                               (int) 
MaxArraySize)));
                        if (addedafter > 1)
                                newhasnulls = true; /* will insert nulls */
                }
@@ -2598,14 +2615,23 @@ array_set_element_expanded(Datum arraydatum,
        addedbefore = addedafter = 0;
 
        /*
-        * Check subscripts (this logic matches original array_set_element)
+        * Check subscripts (this logic must match array_set_element).  We 
assume
+        * the existing subscripts passed ArrayCheckBounds, so that dim[i] + 
lb[i]
+        * can be computed without overflow.  But we must beware of other
+        * overflows in our calculations of new dim[] values.
         */
        if (ndim == 1)
        {
                if (indx[0] < lb[0])
                {
-                       addedbefore = lb[0] - indx[0];
-                       dim[0] += addedbefore;
+                       /* addedbefore = lb[0] - indx[0]; */
+                       /* dim[0] += addedbefore; */
+                       if (pg_sub_s32_overflow(lb[0], indx[0], &addedbefore) ||
+                               pg_add_s32_overflow(dim[0], addedbefore, 
&dim[0]))
+                               ereport(ERROR,
+                                               
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+                                                errmsg("array size exceeds the 
maximum allowed (%d)",
+                                                               (int) 
MaxArraySize)));
                        lb[0] = indx[0];
                        dimschanged = true;
                        if (addedbefore > 1)
@@ -2613,8 +2639,15 @@ array_set_element_expanded(Datum arraydatum,
                }
                if (indx[0] >= (dim[0] + lb[0]))
                {
-                       addedafter = indx[0] - (dim[0] + lb[0]) + 1;
-                       dim[0] += addedafter;
+                       /* addedafter = indx[0] - (dim[0] + lb[0]) + 1; */
+                       /* dim[0] += addedafter; */
+                       if (pg_sub_s32_overflow(indx[0], dim[0] + lb[0], 
&addedafter) ||
+                               pg_add_s32_overflow(addedafter, 1, &addedafter) 
||
+                               pg_add_s32_overflow(dim[0], addedafter, 
&dim[0]))
+                               ereport(ERROR,
+                                               
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+                                                errmsg("array size exceeds the 
maximum allowed (%d)",
+                                                               (int) 
MaxArraySize)));
                        dimschanged = true;
                        if (addedafter > 1)
                                newhasnulls = true; /* will insert nulls */
@@ -2897,7 +2930,10 @@ array_set_slice(Datum arraydatum,
        addedbefore = addedafter = 0;
 
        /*
-        * Check subscripts
+        * Check subscripts.  We assume the existing subscripts passed
+        * ArrayCheckBounds, so that dim[i] + lb[i] can be computed without
+        * overflow.  But we must beware of other overflows in our calculations 
of
+        * new dim[] values.
         */
        if (ndim == 1)
        {
@@ -2912,18 +2948,31 @@ array_set_slice(Datum arraydatum,
                                         errmsg("upper bound cannot be less 
than lower bound")));
                if (lowerIndx[0] < lb[0])
                {
-                       if (upperIndx[0] < lb[0] - 1)
-                               newhasnulls = true; /* will insert nulls */
-                       addedbefore = lb[0] - lowerIndx[0];
-                       dim[0] += addedbefore;
+                       /* addedbefore = lb[0] - lowerIndx[0]; */
+                       /* dim[0] += addedbefore; */
+                       if (pg_sub_s32_overflow(lb[0], lowerIndx[0], 
&addedbefore) ||
+                               pg_add_s32_overflow(dim[0], addedbefore, 
&dim[0]))
+                               ereport(ERROR,
+                                               
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+                                                errmsg("array size exceeds the 
maximum allowed (%d)",
+                                                               (int) 
MaxArraySize)));
                        lb[0] = lowerIndx[0];
+                       if (addedbefore > 1)
+                               newhasnulls = true; /* will insert nulls */
                }
                if (upperIndx[0] >= (dim[0] + lb[0]))
                {
-                       if (lowerIndx[0] > (dim[0] + lb[0]))
+                       /* addedafter = upperIndx[0] - (dim[0] + lb[0]) + 1; */
+                       /* dim[0] += addedafter; */
+                       if (pg_sub_s32_overflow(upperIndx[0], dim[0] + lb[0], 
&addedafter) ||
+                               pg_add_s32_overflow(addedafter, 1, &addedafter) 
||
+                               pg_add_s32_overflow(dim[0], addedafter, 
&dim[0]))
+                               ereport(ERROR,
+                                               
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+                                                errmsg("array size exceeds the 
maximum allowed (%d)",
+                                                               (int) 
MaxArraySize)));
+                       if (addedafter > 1)
                                newhasnulls = true; /* will insert nulls */
-                       addedafter = upperIndx[0] - (dim[0] + lb[0]) + 1;
-                       dim[0] += addedafter;
                }
        }
        else
diff --git a/src/backend/utils/adt/arrayutils.c 
b/src/backend/utils/adt/arrayutils.c
index 6988edd936..fdaf712883 100644
--- a/src/backend/utils/adt/arrayutils.c
+++ b/src/backend/utils/adt/arrayutils.c
@@ -64,10 +64,6 @@ ArrayGetOffset0(int n, const int *tup, const int *scale)
  * This must do overflow checking, since it is used to validate that a user
  * dimensionality request doesn't overflow what we can handle.
  *
- * We limit array sizes to at most about a quarter billion elements,
- * so that it's not necessary to check for overflow in quite so many
- * places --- for instance when palloc'ing Datum arrays.
- *
  * The multiplication overflow check only works on machines that have int64
  * arithmetic, but that is nearly all platforms these days, and doing check
  * divides for those that don't seems way too expensive.
@@ -78,8 +74,6 @@ ArrayGetNItems(int ndim, const int *dims)
        int32           ret;
        int                     i;
 
-#define MaxArraySize ((Size) (MaxAllocSize / sizeof(Datum)))
-
        if (ndim <= 0)
                return 0;
        ret = 1;
diff --git a/src/include/utils/array.h b/src/include/utils/array.h
index a32ba2f510..41a327352e 100644
--- a/src/include/utils/array.h
+++ b/src/include/utils/array.h
@@ -73,6 +73,12 @@ struct ExprContext;
  * Maximum number of array subscripts (arbitrary limit)
  */
 #define MAXDIM 6
+/*
+ * Maximum number of elements in an array.  We limit this to at most about a
+ * quarter billion elements, so that it's not necessary to check for overflow
+ * in quite so many places --- for instance when palloc'ing Datum arrays.
+ */
+#define MaxArraySize ((Size) (MaxAllocSize / sizeof(Datum)))
 
 /*
  * Arrays are varlena objects, so must meet the varlena convention that
diff --git a/src/test/regress/expected/arrays.out 
b/src/test/regress/expected/arrays.out
index c5408a683e..a868640540 100644
--- a/src/test/regress/expected/arrays.out
+++ b/src/test/regress/expected/arrays.out
@@ -1400,6 +1400,23 @@ insert into arr_pk_tbl(pk, f1[1:2]) values (1, 
'{6,7,8}') on conflict (pk)
 -- then you didn't get an indexscan plan, and something is busted.
 reset enable_seqscan;
 reset enable_bitmapscan;
+-- test subscript overflow detection
+-- The normal error message includes a platform-dependent limit,
+-- so suppress it to avoid needing multiple expected-files.
+\set VERBOSITY sqlstate
+insert into arr_pk_tbl values(10, '[-2147483648:-2147483647]={1,2}');
+update arr_pk_tbl set f1[2147483647] = 42 where pk = 10;
+ERROR:  54000
+update arr_pk_tbl set f1[2147483646:2147483647] = array[4,2] where pk = 10;
+ERROR:  54000
+-- also exercise the expanded-array case
+do $$ declare a int[];
+begin
+  a := '[-2147483648:-2147483647]={1,2}'::int[];
+  a[2147483647] := 42;
+end $$;
+ERROR:  54000
+\set VERBOSITY default
 -- test [not] (like|ilike) (any|all) (...)
 select 'foo' like any (array['%a', '%o']); -- t
  ?column? 
diff --git a/src/test/regress/sql/arrays.sql b/src/test/regress/sql/arrays.sql
index 6a69eba245..d10278e32f 100644
--- a/src/test/regress/sql/arrays.sql
+++ b/src/test/regress/sql/arrays.sql
@@ -420,6 +420,25 @@ insert into arr_pk_tbl(pk, f1[1:2]) values (1, '{6,7,8}') 
on conflict (pk)
 reset enable_seqscan;
 reset enable_bitmapscan;
 
+-- test subscript overflow detection
+
+-- The normal error message includes a platform-dependent limit,
+-- so suppress it to avoid needing multiple expected-files.
+\set VERBOSITY sqlstate
+
+insert into arr_pk_tbl values(10, '[-2147483648:-2147483647]={1,2}');
+update arr_pk_tbl set f1[2147483647] = 42 where pk = 10;
+update arr_pk_tbl set f1[2147483646:2147483647] = array[4,2] where pk = 10;
+
+-- also exercise the expanded-array case
+do $$ declare a int[];
+begin
+  a := '[-2147483648:-2147483647]={1,2}'::int[];
+  a[2147483647] := 42;
+end $$;
+
+\set VERBOSITY default
+
 -- test [not] (like|ilike) (any|all) (...)
 select 'foo' like any (array['%a', '%o']); -- t
 select 'foo' like any (array['%a', '%b']); -- f


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