From 83ac0144fa3041556aa4f3952ebd979e0189a19c Mon Sep 17 00:00:00 2001 From: Neal Norwitz Date: Mon, 28 Jul 2008 05:06:20 +0000 Subject: Backport code from r65182: Issue #2620: Overflow checking when allocating or reallocating memory was not always being done properly in some python types and extension modules. PyMem_MALLOC, PyMem_REALLOC, PyMem_NEW and PyMem_RESIZE have all been updated to perform better checks and places in the code that would previously leak memory on the error path when such an allocation failed have been fixed. --- Include/pymem.h | 33 ++++++++++++++++++++++----------- Misc/NEWS | 7 +++++++ Modules/almodule.c | 2 ++ Modules/arraymodule.c | 8 +++++--- Modules/selectmodule.c | 4 +++- Objects/obmalloc.c | 18 ++++++++++++++++++ 6 files changed, 57 insertions(+), 15 deletions(-) diff --git a/Include/pymem.h b/Include/pymem.h index 0ab9463..caa58b1 100644 --- a/Include/pymem.h +++ b/Include/pymem.h @@ -67,8 +67,12 @@ PyAPI_FUNC(void) PyMem_Free(void *); for malloc(0), which would be treated as an error. Some platforms would return a pointer with no memory behind it, which would break pymalloc. To solve these problems, allocate an extra byte. */ -#define PyMem_MALLOC(n) malloc((n) ? (n) : 1) -#define PyMem_REALLOC(p, n) realloc((p), (n) ? (n) : 1) +/* Returns NULL to indicate error if a negative size or size larger than + Py_ssize_t can represent is supplied. Helps prevents security holes. */ +#define PyMem_MALLOC(n) (((n) < 0 || (n) > PY_SSIZE_T_MAX) ? NULL \ + : malloc((n) ? (n) : 1)) +#define PyMem_REALLOC(p, n) (((n) < 0 || (n) > PY_SSIZE_T_MAX) ? NULL \ + : realloc((p), (n) ? (n) : 1)) #define PyMem_FREE free #endif /* PYMALLOC_DEBUG */ @@ -77,24 +81,31 @@ PyAPI_FUNC(void) PyMem_Free(void *); * Type-oriented memory interface * ============================== * - * These are carried along for historical reasons. There's rarely a good - * reason to use them anymore (you can just as easily do the multiply and - * cast yourself). + * Allocate memory for n objects of the given type. Returns a new pointer + * or NULL if the request was too large or memory allocation failed. Use + * these macros rather than doing the multiplication yourself so that proper + * overflow checking is always done. */ #define PyMem_New(type, n) \ - ( assert((n) <= PY_SIZE_MAX / sizeof(type)) , \ + ( ((n) > PY_SSIZE_T_MAX / sizeof(type)) ? NULL : \ ( (type *) PyMem_Malloc((n) * sizeof(type)) ) ) #define PyMem_NEW(type, n) \ - ( assert((n) <= PY_SIZE_MAX / sizeof(type)) , \ + ( ((n) > PY_SSIZE_T_MAX / sizeof(type)) ? NULL : \ ( (type *) PyMem_MALLOC((n) * sizeof(type)) ) ) +/* + * The value of (p) is always clobbered by this macro regardless of success. + * The caller MUST check if (p) is NULL afterwards and deal with the memory + * error if so. This means the original value of (p) MUST be saved for the + * caller's memory error handler to not lose track of it. + */ #define PyMem_Resize(p, type, n) \ - ( assert((n) <= PY_SIZE_MAX / sizeof(type)) , \ - ( (p) = (type *) PyMem_Realloc((p), (n) * sizeof(type)) ) ) + ( (p) = ((n) > PY_SSIZE_T_MAX / sizeof(type)) ? NULL : \ + (type *) PyMem_Realloc((p), (n) * sizeof(type)) ) #define PyMem_RESIZE(p, type, n) \ - ( assert((n) <= PY_SIZE_MAX / sizeof(type)) , \ - ( (p) = (type *) PyMem_REALLOC((p), (n) * sizeof(type)) ) ) + ( (p) = ((n) > PY_SSIZE_T_MAX / sizeof(type)) ? NULL : \ + (type *) PyMem_REALLOC((p), (n) * sizeof(type)) ) /* PyMem{Del,DEL} are left over from ancient days, and shouldn't be used * anymore. They're just confusing aliases for PyMem_{Free,FREE} now. diff --git a/Misc/NEWS b/Misc/NEWS index 0f36f17..222e408 100644 --- a/Misc/NEWS +++ b/Misc/NEWS @@ -12,6 +12,13 @@ What's New in Python 2.5.3? Core and builtins ----------------- +- Issue #2620: Overflow checking when allocating or reallocating memory + was not always being done properly in some python types and extension + modules. PyMem_MALLOC, PyMem_REALLOC, PyMem_NEW and PyMem_RESIZE have + all been updated to perform better checks and places in the code that + would previously leak memory on the error path when such an allocation + failed have been fixed. + - Issue #2242: Fix a crash when decoding invalid utf-7 input on certain Windows / Visual Studio versions. diff --git a/Modules/almodule.c b/Modules/almodule.c index 0a45d2e..e4481cd 100644 --- a/Modules/almodule.c +++ b/Modules/almodule.c @@ -1633,9 +1633,11 @@ al_QueryValues(PyObject *self, PyObject *args) if (nvals < 0) goto cleanup; if (nvals > setsize) { + ALvalue *old_return_set = return_set; setsize = nvals; PyMem_RESIZE(return_set, ALvalue, setsize); if (return_set == NULL) { + return_set = old_return_set; PyErr_NoMemory(); goto cleanup; } diff --git a/Modules/arraymodule.c b/Modules/arraymodule.c index eafea98..f262d20 100644 --- a/Modules/arraymodule.c +++ b/Modules/arraymodule.c @@ -816,6 +816,7 @@ static int array_do_extend(arrayobject *self, PyObject *bb) { Py_ssize_t size; + char *old_item; if (!array_Check(bb)) return array_iter_extend(self, bb); @@ -831,10 +832,11 @@ array_do_extend(arrayobject *self, PyObject *bb) return -1; } size = self->ob_size + b->ob_size; + old_item = self->ob_item; PyMem_RESIZE(self->ob_item, char, size*self->ob_descr->itemsize); if (self->ob_item == NULL) { - PyObject_Del(self); - PyErr_NoMemory(); + self->ob_item = old_item; + PyErr_NoMemory(); return -1; } memcpy(self->ob_item + self->ob_size*self->ob_descr->itemsize, @@ -886,7 +888,7 @@ array_inplace_repeat(arrayobject *self, Py_ssize_t n) if (size > PY_SSIZE_T_MAX / n) { return PyErr_NoMemory(); } - PyMem_Resize(items, char, n * size); + PyMem_RESIZE(items, char, n * size); if (items == NULL) return PyErr_NoMemory(); p = items; diff --git a/Modules/selectmodule.c b/Modules/selectmodule.c index 9eaae84..4deab6f 100644 --- a/Modules/selectmodule.c +++ b/Modules/selectmodule.c @@ -349,10 +349,12 @@ update_ufd_array(pollObject *self) { Py_ssize_t i, pos; PyObject *key, *value; + struct pollfd *old_ufds = self->ufds; self->ufd_len = PyDict_Size(self->dict); - PyMem_Resize(self->ufds, struct pollfd, self->ufd_len); + PyMem_RESIZE(self->ufds, struct pollfd, self->ufd_len); if (self->ufds == NULL) { + self->ufds = old_ufds; PyErr_NoMemory(); return 0; } diff --git a/Objects/obmalloc.c b/Objects/obmalloc.c index 03add6b..2d77906 100644 --- a/Objects/obmalloc.c +++ b/Objects/obmalloc.c @@ -727,6 +727,15 @@ PyObject_Malloc(size_t nbytes) uint size; /* + * Limit ourselves to PY_SSIZE_T_MAX bytes to prevent security holes. + * Most python internals blindly use a signed Py_ssize_t to track + * things without checking for overflows or negatives. + * As size_t is unsigned, checking for nbytes < 0 is not required. + */ + if (nbytes > PY_SSIZE_T_MAX) + return NULL; + + /* * This implicitly redirects malloc(0). */ if ((nbytes - 1) < SMALL_REQUEST_THRESHOLD) { @@ -1130,6 +1139,15 @@ PyObject_Realloc(void *p, size_t nbytes) if (p == NULL) return PyObject_Malloc(nbytes); + /* + * Limit ourselves to PY_SSIZE_T_MAX bytes to prevent security holes. + * Most python internals blindly use a signed Py_ssize_t to track + * things without checking for overflows or negatives. + * As size_t is unsigned, checking for nbytes < 0 is not required. + */ + if (nbytes > PY_SSIZE_T_MAX) + return NULL; + pool = POOL_ADDR(p); if (Py_ADDRESS_IN_RANGE(p, pool)) { /* We're in charge of this block */ -- cgit v0.12