Re: [Tarantool-patches] [PATCH] Memtx_tuple_delete used heap after free

[Alexander Turenko <alexander.turenko@tarantool.org>]

On Mon, Jan 13, 2020 at 07:45:48PM +0300, Cyrill Gorcunov wrote:
> On Fri, Dec 06, 2019 at 02:29:25PM +0300, Maria Khaydich wrote:
> >    Overlooked a better solution as @PersDep kindly suggested. Sending the
> >    fixed version. 
> >     
> >    Subject: [PATCH] Memtx_tuple_delete used heap after free
> >    Struct of type tuple_format is being passed as
> >    an argument to tuple_format_unref where it might
> >    be freed. On such occasion any further references
> >    to format fields should not take place.
> >     
> >    Closes #4658
> >    ---
> >    Issue:
> >    https://github.com/tarantool/tarantool/issues/4658
> >    Branch:
> >    https://github.com/tarantool/tarantool/compare/eljashm/gh-4658-heap-use-after-free
> >     
> >     src/box/memtx_engine.c | 2 +-
> >     1 file changed, 1 insertion(+), 1 deletion(-)
> >     
> >    diff --git a/src/box/memtx_engine.c b/src/box/memtx_engine.c
> >    index 23ccc4703..4da80824a 100644
> >    --- a/src/box/memtx_engine.c
> >    +++ b/src/box/memtx_engine.c
> >    @@ -1177,7 +1177,6 @@ memtx_tuple_delete(struct tuple_format *format,
> >    struct tuple *tuple)
> >         struct memtx_engine *memtx = (struct memtx_engine *)format->engine;
> >         say_debug("%s(%p)", __func__, tuple);
> >         assert(tuple->refs == 0);
> >    -    tuple_format_unref(format);
> >         struct memtx_tuple *memtx_tuple =
> >             container_of(tuple, struct memtx_tuple, base);
> >         size_t total = tuple_size(tuple) + offsetof(struct memtx_tuple,
> >    base);
> >    @@ -1187,6 +1186,7 @@ memtx_tuple_delete(struct tuple_format *format,
> >    struct tuple *tuple)
> >             smfree(&memtx->alloc, memtx_tuple, total);
> >         else
> >             smfree_delayed(&memtx->alloc, memtx_tuple, total);
> >    +    tuple_format_unref(format);
> >     }
> 
> So we basically defer unref.
> Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com>

LGTM too (it was already pushed to the master, but I looked anyway).

> 
> FWIW the use after free introduced by the commit f9299c43d4fcc918a98c45563a5f96bb13863337

Added to the issue just in case.

WBR, Alexander Turenko.