From a9dafdd57c71473fa3a2ec4887e973e4e9876d83 Mon Sep 17 00:00:00 2001 From: Michal Srb Date: Thu, 15 Mar 2018 09:50:58 +0100 Subject: [PATCH libX11] Use flexible array member instead of fake size. The _XimCacheStruct structure is followed in memory by two strings containing fname and encoding. The memory was accessed using the last member of the structure `char fname[1]`. That is a lie, prohibits us from using sizeof and confuses checkers. Lets declare it properly as a flexible array, so compilers don't complain about writing past that array. As bonus we can replace the XOffsetOf with regular sizeof. Fixes GCC8 error: In function 'strcpy', inlined from '_XimWriteCachedDefaultTree' at imLcIm.c:479:5, inlined from '_XimCreateDefaultTree' at imLcIm.c:616:2, inlined from '_XimLocalOpenIM' at imLcIm.c:700:5: /usr/include/bits/string_fortified.h:90:10: error: '__builtin_strcpy' forming offset 2 is out of the bounds [0, 1] [-Werror=array-bounds] return __builtin___strcpy_chk (__dest, __src, __bos (__dest)); Caused by this line seemingly writing past the fname[1] array: imLcIm.c:479: strcpy (m->fname+strlen(name)+1, encoding); Reviewed-by: Keith Packard Signed-off-by: Peter Hutterer --- modules/im/ximcp/imLcIm.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/modules/im/ximcp/imLcIm.c b/modules/im/ximcp/imLcIm.c index c19695df..743df77b 100644 --- a/modules/im/ximcp/imLcIm.c +++ b/modules/im/ximcp/imLcIm.c @@ -82,8 +82,8 @@ struct _XimCacheStruct { DTCharIndex mbused; DTCharIndex wcused; DTCharIndex utf8used; - char fname[1]; - /* char encoding[1] */ + char fname[]; + /* char encoding[] */ }; static struct _XimCacheStruct* _XimCache_mmap = NULL; @@ -281,7 +281,7 @@ _XimReadCachedDefaultTree( assert (m->id == XIM_CACHE_MAGIC); assert (m->version == XIM_CACHE_VERSION); if (size != m->size || - size < XOffsetOf (struct _XimCacheStruct, fname) + namelen + encodinglen) { + size < sizeof (struct _XimCacheStruct) + namelen + encodinglen) { fprintf (stderr, "Ignoring broken XimCache %s [%s]\n", name, encoding); munmap (m, size); return False; @@ -442,7 +442,7 @@ _XimWriteCachedDefaultTree( int fd; FILE *fp; struct _XimCacheStruct *m; - int msize = (XOffsetOf(struct _XimCacheStruct, fname) + int msize = (sizeof(struct _XimCacheStruct) + strlen(name) + strlen(encoding) + 2 + XIM_CACHE_TREE_ALIGNMENT-1) & -XIM_CACHE_TREE_ALIGNMENT; DefTreeBase *b = &im->private.local.base; -- 2.14.3