From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Liu Subject: Re: [PATCH v2] tools: libxl: make it illegal to pass libxl__realloc(gc) a non-gc ptr Date: Thu, 11 Feb 2016 11:37:13 +0000 Message-ID: <20160211113712.GH17384@citrix.com> References: <1455182634-19386-1-git-send-email-ian.campbell@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1455182634-19386-1-git-send-email-ian.campbell@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell Cc: wei.liu2@citrix.com, ian.jackson@eu.citrix.com, xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On Thu, Feb 11, 2016 at 09:23:54AM +0000, Ian Campbell wrote: > That is, if gc is not NOGC and ptr is not NULL then ptr must be > associated gc. > "associated with gc"? Anyway, I get the idea. > Currently in this case the new_ptr would not be registered with any > gc, which Coverity rightly points out (in various different places) > would be a memory leak. > > It would also be possible to fix this by adding a libxl__ptr_add() at > the same point, however semantically it seems like a programming error > to gc-realloc a pointer which is not associated with the gc in > question, so treat it as such. > > Compile tested only, this change could expose latent bugs. > > Signed-off-by: Ian Campbell Acked-by: Wei Liu > --- > v2: Check we actually didn't find the ptr in the gc > Correct log message and shorten since LOG will inject the > function name. > --- > tools/libxl/libxl_internal.c | 4 ++++ > tools/libxl/libxl_internal.h | 4 +++- > 2 files changed, 7 insertions(+), 1 deletion(-) > > diff --git a/tools/libxl/libxl_internal.c b/tools/libxl/libxl_internal.c > index 328046b..fc81130 100644 > --- a/tools/libxl/libxl_internal.c > +++ b/tools/libxl/libxl_internal.c > @@ -122,6 +122,10 @@ void *libxl__realloc(libxl__gc *gc, void *ptr, size_t new_size) > break; > } > } > + if (i == gc->alloc_maxsize) { > + LOG(CRITICAL, "pointer is not tracked by the given gc"); > + abort(); > + } > } > > return new_ptr; > diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h > index fc1b558..650a958 100644 > --- a/tools/libxl/libxl_internal.h > +++ b/tools/libxl/libxl_internal.h > @@ -617,7 +617,9 @@ _hidden void *libxl__zalloc(libxl__gc *gc_opt, size_t size) NN1; > _hidden void *libxl__calloc(libxl__gc *gc_opt, size_t nmemb, size_t size) NN1; > /* change the size of the memory block pointed to by @ptr to @new_size bytes. > * unlike other allocation functions here any additional space between the > - * oldsize and @new_size is not initialised (similar to a gc'd realloc(3)). */ > + * oldsize and @new_size is not initialised (similar to a gc'd realloc(3)). > + * if @ptr is non-NULL and @gc_opt is not nogc_gc then @ptr must have been > + * registered with @gc_opt previously. */ > _hidden void *libxl__realloc(libxl__gc *gc_opt, void *ptr, size_t new_size) NN1; > /* print @fmt into an allocated string large enoughto contain the result. > * (similar to gc'd asprintf(3)). */ > -- > 2.1.4 >