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https://gitlab.com/libvirt/libvirt.git
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memory: make it safer to expand arrays
* src/util/memory.h (VIR_REALLOC_N): Update docs. (VIR_EXPAND_N, VIR_SHRINK_N): New macros. (virAlloc, virAllocN, virReallocN, virAllocVar, virFree): Add some gcc attributes. * src/util/memory.c (virExpandN, virShrinkN): New functions. (virReallocN): Update docs. * src/libvirt_private.syms: Export new helpers. * docs/hacking.html.in: Prefer newer interfaces over VIR_REALLOC_N, since uninitialized memory can bite us. * HACKING: Regenerate.
This commit is contained in:
parent
b503022e57
commit
5a0beacc12
38
HACKING
38
HACKING
@ -280,9 +280,9 @@ Low level memory management
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Use of the malloc/free/realloc/calloc APIs is deprecated in the libvirt
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codebase, because they encourage a number of serious coding bugs and do not
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enable compile time verification of checks for NULL. Instead of these
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routines, use the macros from memory.h
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routines, use the macros from memory.h.
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- e.g. to allocate a single object:
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- To allocate a single object:
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virDomainPtr domain;
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@ -293,10 +293,10 @@ routines, use the macros from memory.h
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- e.g. to allocate an array of objects
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- To allocate an array of objects:
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virDomainPtr domains;
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int ndomains = 10;
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size_t ndomains = 10;
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if (VIR_ALLOC_N(domains, ndomains) < 0) {
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virReportOOMError();
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@ -305,7 +305,7 @@ routines, use the macros from memory.h
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- e.g. to allocate an array of object pointers
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- To allocate an array of object pointers:
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virDomainPtr *domains;
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int ndomains = 10;
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@ -317,18 +317,22 @@ routines, use the macros from memory.h
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- e.g. to re-allocate the array of domains to be longer
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- To re-allocate the array of domains to be longer:
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ndomains = 20
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if (VIR_REALLOC_N(domains, ndomains) < 0) {
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if (VIR_EXPAND_N(domains, ndomains, 10) < 0) {
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virReportOOMError();
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return NULL;
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}
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- e.g. to free the domain
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- To trim an array of domains to have one less element:
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VIR_SHRINK_N(domains, ndomains, 1);
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- To free the domain:
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VIR_FREE(domain);
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@ -344,7 +348,7 @@ code base to help avoiding double-closing of files or file descriptors, which
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is particulary dangerous in a multi-threaded applications. Instead of these
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APIs, use the macros from files.h
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- eg opening a file from a file descriptor
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- Open a file from a file descriptor:
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if ((file = VIR_FDOPEN(fd, "r")) == NULL) {
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virReportSystemError(errno, "%s",
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@ -355,7 +359,7 @@ APIs, use the macros from files.h
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- e.g. close a file descriptor
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- Close a file descriptor:
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if (VIR_CLOSE(fd) < 0) {
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virReportSystemError(errno, "%s", _("failed to close file"));
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@ -363,7 +367,7 @@ APIs, use the macros from files.h
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- eg close a file
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- Close a file:
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if (VIR_FCLOSE(file) < 0) {
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virReportSystemError(errno, "%s", _("failed to close file"));
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@ -371,8 +375,8 @@ APIs, use the macros from files.h
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- eg close a file or file descriptor in an error path, without losing the
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previous "errno" value
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- Close a file or file descriptor in an error path, without losing the previous
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"errno" value:
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VIR_FORCE_CLOSE(fd);
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VIR_FORCE_FCLOSE(file);
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@ -460,7 +464,7 @@ If there is a need for complex string concatenations, avoid using the usual
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sequence of malloc/strcpy/strcat/snprintf functions and make use of the
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virBuffer API described in buf.h
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eg typical usage is as follows:
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Typical usage is as follows:
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char *
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somefunction(...)
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@ -594,7 +598,7 @@ When using goto, please use one of these standard labels if it makes sense:
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error: A path only taken upon return with an error code
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cleanup: A path taken upon return with success code + optional error
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no_memory: A path only taken upon return with an OOM error code
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retry: If needing to jump upwards (eg retry on EINTR)
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retry: If needing to jump upwards (e.g., retry on EINTR)
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Libvirt committer guidelines
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@ -354,11 +354,12 @@
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Use of the malloc/free/realloc/calloc APIs is deprecated in the libvirt
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codebase, because they encourage a number of serious coding bugs and do
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not enable compile time verification of checks for NULL. Instead of these
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routines, use the macros from memory.h
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routines, use the macros from memory.h.
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</p>
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<ul>
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<li><p>e.g. to allocate a single object:</p>
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<li><p>To allocate a single object:</p>
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<pre>
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virDomainPtr domain;
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@ -369,10 +370,10 @@
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</pre>
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</li>
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<li><p>e.g. to allocate an array of objects</p>
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<li><p>To allocate an array of objects:</p>
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<pre>
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virDomainPtr domains;
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int ndomains = 10;
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size_t ndomains = 10;
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if (VIR_ALLOC_N(domains, ndomains) < 0) {
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virReportOOMError();
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@ -381,7 +382,7 @@
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</pre>
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</li>
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<li><p>e.g. to allocate an array of object pointers</p>
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<li><p>To allocate an array of object pointers:</p>
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<pre>
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virDomainPtr *domains;
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int ndomains = 10;
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@ -393,18 +394,22 @@
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</pre>
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</li>
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<li><p>e.g. to re-allocate the array of domains to be longer</p>
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<li><p>To re-allocate the array of domains to be longer:</p>
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<pre>
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ndomains = 20
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if (VIR_REALLOC_N(domains, ndomains) < 0) {
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if (VIR_EXPAND_N(domains, ndomains, 10) < 0) {
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virReportOOMError();
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return NULL;
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}
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</pre>
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</li>
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<li><p>e.g. to free the domain</p>
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<li><p>To trim an array of domains to have one less element:</p>
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<pre>
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VIR_SHRINK_N(domains, ndomains, 1);
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</pre></li>
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<li><p>To free the domain:</p>
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<pre>
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VIR_FREE(domain);
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</pre>
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@ -421,7 +426,7 @@
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</p>
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<ul>
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<li><p>eg opening a file from a file descriptor</p>
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<li><p>Open a file from a file descriptor:</p>
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<pre>
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if ((file = VIR_FDOPEN(fd, "r")) == NULL) {
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@ -432,14 +437,14 @@
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/* fd is now invalid; only access the file using file variable */
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</pre></li>
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<li><p>e.g. close a file descriptor</p>
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<li><p>Close a file descriptor:</p>
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<pre>
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if (VIR_CLOSE(fd) < 0) {
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virReportSystemError(errno, "%s", _("failed to close file"));
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}
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</pre></li>
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<li><p>eg close a file</p>
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<li><p>Close a file:</p>
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<pre>
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if (VIR_FCLOSE(file) < 0) {
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@ -447,8 +452,8 @@
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}
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</pre></li>
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<li><p>eg close a file or file descriptor in an error path, without losing
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the previous <code>errno</code> value</p>
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<li><p>Close a file or file descriptor in an error path, without losing
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the previous <code>errno</code> value:</p>
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<pre>
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VIR_FORCE_CLOSE(fd);
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@ -554,7 +559,7 @@
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make use of the virBuffer API described in buf.h
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</p>
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<p>eg typical usage is as follows:</p>
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<p>Typical usage is as follows:</p>
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<pre>
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char *
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@ -722,7 +727,7 @@
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error: A path only taken upon return with an error code
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cleanup: A path taken upon return with success code + optional error
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no_memory: A path only taken upon return with an OOM error code
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retry: If needing to jump upwards (eg retry on EINTR)
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retry: If needing to jump upwards (e.g., retry on EINTR)
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</pre>
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@ -503,8 +503,10 @@ virLogUnlock;
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# memory.h
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virAlloc;
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virAllocN;
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virExpandN;
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virFree;
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virReallocN;
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virShrinkN;
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# network.h
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@ -1,6 +1,7 @@
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/*
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* memory.c: safer memory allocation
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*
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* Copyright (C) 2010 Red Hat, Inc.
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* Copyright (C) 2008 Daniel P. Berrange
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*
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* This library is free software; you can redistribute it and/or
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@ -24,6 +25,7 @@
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#include <stddef.h>
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#include "memory.h"
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#include "ignore-value.h"
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#if TEST_OOM
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@ -141,7 +143,7 @@ int virAllocN(void *ptrptr, size_t size, size_t count)
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* 'count' elements, each 'size' bytes in length. Update 'ptrptr'
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* with the address of the newly allocated memory. On failure,
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* 'ptrptr' is not changed and still points to the original memory
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* block. The newly allocated memory is filled with zeros.
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* block. Any newly allocated memory in 'ptrptr' is uninitialized.
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*
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* Returns -1 on failure to allocate, zero on success
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*/
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@ -164,6 +166,61 @@ int virReallocN(void *ptrptr, size_t size, size_t count)
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return 0;
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}
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/**
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* virExpandN:
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* @ptrptr: pointer to pointer for address of allocated memory
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* @size: number of bytes per element
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* @countptr: pointer to number of elements in array
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* @add: number of elements to add
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*
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* Resize the block of memory in 'ptrptr' to be an array of
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* '*countptr' + 'add' elements, each 'size' bytes in length.
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* Update 'ptrptr' and 'countptr' with the details of the newly
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* allocated memory. On failure, 'ptrptr' and 'countptr' are not
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* changed. Any newly allocated memory in 'ptrptr' is zero-filled.
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*
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* Returns -1 on failure to allocate, zero on success
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*/
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int virExpandN(void *ptrptr, size_t size, size_t *countptr, size_t add)
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{
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int ret;
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if (*countptr + add < *countptr) {
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errno = ENOMEM;
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return -1;
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}
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ret = virReallocN(ptrptr, size, *countptr + add);
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if (ret == 0) {
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memset(*(char **)ptrptr + (size * *countptr), 0, size * add);
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*countptr += add;
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}
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return ret;
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}
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/**
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* virShrinkN:
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* @ptrptr: pointer to pointer for address of allocated memory
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* @size: number of bytes per element
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* @countptr: pointer to number of elements in array
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* @remove: number of elements to remove
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*
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* Resize the block of memory in 'ptrptr' to be an array of
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* '*countptr' - 'remove' elements, each 'size' bytes in length.
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* Update 'ptrptr' and 'countptr' with the details of the newly
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* allocated memory. If 'remove' is larger than 'countptr', free
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* the entire array.
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*/
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void virShrinkN(void *ptrptr, size_t size, size_t *countptr, size_t remove)
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{
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if (remove < *countptr)
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ignore_value(virReallocN(ptrptr, size, *countptr -= remove));
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else {
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virFree(ptrptr);
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*countptr = 0;
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}
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}
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/**
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* Vir_Alloc_Var:
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* @ptrptr: pointer to hold address of allocated memory
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@ -46,14 +46,21 @@
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/* Don't call these directly - use the macros below */
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int virAlloc(void *ptrptr, size_t size) ATTRIBUTE_RETURN_CHECK;
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int virAllocN(void *ptrptr, size_t size, size_t count) ATTRIBUTE_RETURN_CHECK;
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int virReallocN(void *ptrptr, size_t size, size_t count) ATTRIBUTE_RETURN_CHECK;
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int virAlloc(void *ptrptr, size_t size) ATTRIBUTE_RETURN_CHECK
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ATTRIBUTE_NONNULL(1);
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int virAllocN(void *ptrptr, size_t size, size_t count) ATTRIBUTE_RETURN_CHECK
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ATTRIBUTE_NONNULL(1);
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int virReallocN(void *ptrptr, size_t size, size_t count) ATTRIBUTE_RETURN_CHECK
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ATTRIBUTE_NONNULL(1);
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int virExpandN(void *ptrptr, size_t size, size_t *count, size_t add)
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ATTRIBUTE_RETURN_CHECK ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(3);
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void virShrinkN(void *ptrptr, size_t size, size_t *count, size_t remove)
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ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(3);
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int virAllocVar(void *ptrptr,
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size_t struct_size,
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size_t element_size,
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size_t count) ATTRIBUTE_RETURN_CHECK;
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void virFree(void *ptrptr);
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size_t count) ATTRIBUTE_RETURN_CHECK ATTRIBUTE_NONNULL(1);
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void virFree(void *ptrptr) ATTRIBUTE_NONNULL(1);
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/**
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* VIR_ALLOC:
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@ -87,12 +94,44 @@ void virFree(void *ptrptr);
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*
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* Re-allocate an array of 'count' elements, each sizeof(*ptr)
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* bytes long and store the address of allocated memory in
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* 'ptr'. Fill the newly allocated memory with zeros
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* 'ptr'. If 'ptr' grew, the added memory is uninitialized.
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*
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* Returns -1 on failure, 0 on success
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*/
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# define VIR_REALLOC_N(ptr, count) virReallocN(&(ptr), sizeof(*(ptr)), (count))
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/**
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* VIR_EXPAND_N:
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* @ptr: pointer to hold address of allocated memory
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* @count: variable tracking number of elements currently allocated
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* @add: number of elements to add
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*
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* Re-allocate an array of 'count' elements, each sizeof(*ptr)
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* bytes long, to be 'count' + 'add' elements long, then store the
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* address of allocated memory in 'ptr' and the new size in 'count'.
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* The new elements are filled with zero.
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*
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* Returns -1 on failure, 0 on success
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*/
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# define VIR_EXPAND_N(ptr, count, add) \
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virExpandN(&(ptr), sizeof(*(ptr)), &(count), add)
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/**
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* VIR_SHRINK_N:
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* @ptr: pointer to hold address of allocated memory
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* @count: variable tracking number of elements currently allocated
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* @remove: number of elements to remove
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*
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* Re-allocate an array of 'count' elements, each sizeof(*ptr)
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* bytes long, to be 'count' - 'remove' elements long, then store the
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* address of allocated memory in 'ptr' and the new size in 'count'.
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* If 'count' <= 'remove', the entire array is freed.
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*
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* No return value.
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*/
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# define VIR_SHRINK_N(ptr, count, remove) \
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virShrinkN(&(ptr), sizeof(*(ptr)), &(count), remove)
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/*
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* VIR_ALLOC_VAR_OVERSIZED:
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* @M: size of base structure
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