| Message ID | 1455125223-4205-1-git-send-email-ian.campbell@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 10/02/16 17:27, Ian Campbell wrote: > That is, if gc is not NOGC and ptr is not NULL then ptr must be > associated gc. > > Currently in this case the new_ptr would not be registered with any > gc, which Coverity rightly points out 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 <ian.campbell@citrix.com> > --- > tools/libxl/libxl_internal.c | 7 +++++++ > tools/libxl/libxl_internal.h | 4 +++- > 2 files changed, 10 insertions(+), 1 deletion(-) > > diff --git a/tools/libxl/libxl_internal.c b/tools/libxl/libxl_internal.c > index 328046b..179d618 100644 > --- a/tools/libxl/libxl_internal.c > +++ b/tools/libxl/libxl_internal.c > @@ -122,6 +122,13 @@ void *libxl__realloc(libxl__gc *gc, void *ptr, size_t new_size) > break; > } > } > + /* > + * If we get here then ptr was not previously registered with > + * this gc. > + */ > + LOG(CRITICAL, > + "libxl__realloc on a pointer which tracked by the given gc"); "is not" ? ~Andrew
On Wed, 2016-02-10 at 17:33 +0000, Andrew Cooper wrote: > On 10/02/16 17:27, Ian Campbell wrote: > > That is, if gc is not NOGC and ptr is not NULL then ptr must be > > associated gc. > > > > Currently in this case the new_ptr would not be registered with any > > gc, which Coverity rightly points out 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 <ian.campbell@citrix.com> > > --- > > tools/libxl/libxl_internal.c | 7 +++++++ > > tools/libxl/libxl_internal.h | 4 +++- > > 2 files changed, 10 insertions(+), 1 deletion(-) > > > > diff --git a/tools/libxl/libxl_internal.c > b/tools/libxl/libxl_internal.c > > index 328046b..179d618 100644 > > --- a/tools/libxl/libxl_internal.c > > +++ b/tools/libxl/libxl_internal.c > > @@ -122,6 +122,13 @@ void *libxl__realloc(libxl__gc *gc, void *ptr, > size_t new_size) > > break; > > } > > } > > + /* > > + * If we get here then ptr was not previously registered > with > > + * this gc. > > + */ > > + LOG(CRITICAL, > > + "libxl__realloc on a pointer which tracked by the > given gc"); > > "is not" ? Yes. More importantly I'd somehow convinced myself that the break in the for loop went one scope further than it did. IOW this code _really_ needs an i == gc->alloc_maxsize check before it makes a fuss! At which point I may just turn it into an assert. Ian.
diff --git a/tools/libxl/libxl_internal.c b/tools/libxl/libxl_internal.c index 328046b..179d618 100644 --- a/tools/libxl/libxl_internal.c +++ b/tools/libxl/libxl_internal.c @@ -122,6 +122,13 @@ void *libxl__realloc(libxl__gc *gc, void *ptr, size_t new_size) break; } } + /* + * If we get here then ptr was not previously registered with + * this gc. + */ + LOG(CRITICAL, + "libxl__realloc on a pointer which 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)). */
That is, if gc is not NOGC and ptr is not NULL then ptr must be associated gc. Currently in this case the new_ptr would not be registered with any gc, which Coverity rightly points out 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 <ian.campbell@citrix.com> --- tools/libxl/libxl_internal.c | 7 +++++++ tools/libxl/libxl_internal.h | 4 +++- 2 files changed, 10 insertions(+), 1 deletion(-)