Re: [PATCH 12/12] reset: clear_unpack_trees_porcelain to plug leak

>
> From: Andrzej Hunt <ajrhunt@google.com>
>
> setup_unpack_trees_porcelain() populates various fields on
> unpack_tree_opts, we need to call clear_unpack_trees_porcelain() to
> avoid leaking them. Specifically, we used to leak
> unpack_tree_opts.msgs_to_free.
>
> We have to do this in leave_reset_head because there are multiple
> scenarios where unpack_tree_opts has already been configured, followed
> by a 'goto leave_reset_head'. But we can also 'goto leave_reset_head'
> prior to having initialised unpack_tree_opts via memset(..., 0, ...).
> Therefore we also move unpack_tree_opts initialisation to the start of
> reset_head(), and convert it to use brace initialisation - which
> guarantees that we can never clear an unitialised unpack_tree_opts.

> clear_unpack_tree_opts() is always safe to call as long as
> unpack_tree_opts is at least zero-initialised, i.e. it does not depend
> on a previous call to setup_unpack_trees_porcelain().
>
> LSAN output from t0021:
>
> Direct leak of 192 byte(s) in 1 object(s) allocated from:
>     #0 0x49ab49 in realloc ../projects/compiler-rt/lib/asan/asan_malloc_linux.cpp:164:3
>     #1 0xa721e5 in xrealloc wrapper.c:126:8
>     #2 0x9f7861 in strvec_push_nodup strvec.c:19:2
>     #3 0x9f7861 in strvec_pushf strvec.c:39:2
>     #4 0xa43e14 in setup_unpack_trees_porcelain unpack-trees.c:129:3
>     #5 0x97e011 in reset_head reset.c:53:2
>     #6 0x61dfa5 in cmd_rebase builtin/rebase.c:1991:9
>     #7 0x4ce83e in run_builtin git.c:475:11
>     #8 0x4ccafe in handle_builtin git.c:729:3
>     #9 0x4cb01c in run_argv git.c:818:4
>     #10 0x4cb01c in cmd_main git.c:949:19
>     #11 0x6b3f3d in main common-main.c:52:11
>     #12 0x7fa8addf3349 in __libc_start_main (/lib64/libc.so.6+0x24349)
>
> Indirect leak of 147 byte(s) in 1 object(s) allocated from:
>     #0 0x49ab49 in realloc ../projects/compiler-rt/lib/asan/asan_malloc_linux.cpp:164:3
>     #1 0xa721e5 in xrealloc wrapper.c:126:8
>     #2 0x9e8d54 in strbuf_grow strbuf.c:98:2
>     #3 0x9e8d54 in strbuf_vaddf strbuf.c:401:3
>     #4 0x9f7774 in strvec_pushf strvec.c:36:2
>     #5 0xa43e14 in setup_unpack_trees_porcelain unpack-trees.c:129:3
>     #6 0x97e011 in reset_head reset.c:53:2
>     #7 0x61dfa5 in cmd_rebase builtin/rebase.c:1991:9
>     #8 0x4ce83e in run_builtin git.c:475:11
>     #9 0x4ccafe in handle_builtin git.c:729:3
>     #10 0x4cb01c in run_argv git.c:818:4
>     #11 0x4cb01c in cmd_main git.c:949:19
>     #12 0x6b3f3d in main common-main.c:52:11
>     #13 0x7fa8addf3349 in __libc_start_main (/lib64/libc.so.6+0x24349)
>
> Indirect leak of 134 byte(s) in 1 object(s) allocated from:
>     #0 0x49ab49 in realloc ../projects/compiler-rt/lib/asan/asan_malloc_linux.cpp:164:3
>     #1 0xa721e5 in xrealloc wrapper.c:126:8
>     #2 0x9e8d54 in strbuf_grow strbuf.c:98:2
>     #3 0x9e8d54 in strbuf_vaddf strbuf.c:401:3
>     #4 0x9f7774 in strvec_pushf strvec.c:36:2
>     #5 0xa43fe4 in setup_unpack_trees_porcelain unpack-trees.c:168:3
>     #6 0x97e011 in reset_head reset.c:53:2
>     #7 0x61dfa5 in cmd_rebase builtin/rebase.c:1991:9
>     #8 0x4ce83e in run_builtin git.c:475:11
>     #9 0x4ccafe in handle_builtin git.c:729:3
>     #10 0x4cb01c in run_argv git.c:818:4
>     #11 0x4cb01c in cmd_main git.c:949:19
>     #12 0x6b3f3d in main common-main.c:52:11
>     #13 0x7fa8addf3349 in __libc_start_main (/lib64/libc.so.6+0x24349)
>
> Indirect leak of 130 byte(s) in 1 object(s) allocated from:
>     #0 0x49ab49 in realloc ../projects/compiler-rt/lib/asan/asan_malloc_linux.cpp:164:3
>     #1 0xa721e5 in xrealloc wrapper.c:126:8
>     #2 0x9e8d54 in strbuf_grow strbuf.c:98:2
>     #3 0x9e8d54 in strbuf_vaddf strbuf.c:401:3
>     #4 0x9f7774 in strvec_pushf strvec.c:36:2
>     #5 0xa43f20 in setup_unpack_trees_porcelain unpack-trees.c:150:3
>     #6 0x97e011 in reset_head reset.c:53:2
>     #7 0x61dfa5 in cmd_rebase builtin/rebase.c:1991:9
>     #8 0x4ce83e in run_builtin git.c:475:11
>     #9 0x4ccafe in handle_builtin git.c:729:3
>     #10 0x4cb01c in run_argv git.c:818:4
>     #11 0x4cb01c in cmd_main git.c:949:19
>     #12 0x6b3f3d in main common-main.c:52:11
>     #13 0x7fa8addf3349 in __libc_start_main (/lib64/libc.so.6+0x24349)
>
> SUMMARY: AddressSanitizer: 603 byte(s) leaked in 4 allocation(s).
>
> Signed-off-by: Andrzej Hunt <andrzej@ahunt.org>
> ---
>  reset.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/reset.c b/reset.c
> index 4bea758053..79310ae071 100644
> --- a/reset.c
> +++ b/reset.c
> @@ -21,7 +21,7 @@ int reset_head(struct repository *r, struct object_id *oid, const char *action,
>         struct object_id head_oid;
>         struct tree_desc desc[2] = { { NULL }, { NULL } };
>         struct lock_file lock = LOCK_INIT;
> -       struct unpack_trees_options unpack_tree_opts;
> +       struct unpack_trees_options unpack_tree_opts = { 0 };
>         struct tree *tree;
>         const char *reflog_action;
>         struct strbuf msg = STRBUF_INIT;
> @@ -49,7 +49,6 @@ int reset_head(struct repository *r, struct object_id *oid, const char *action,
>         if (refs_only)
>                 goto reset_head_refs;
>
> -       memset(&unpack_tree_opts, 0, sizeof(unpack_tree_opts));
>         setup_unpack_trees_porcelain(&unpack_tree_opts, action);
>         unpack_tree_opts.head_idx = 1;
>         unpack_tree_opts.src_index = r->index;
> @@ -134,6 +133,7 @@ int reset_head(struct repository *r, struct object_id *oid, const char *action,
>  leave_reset_head:
>         strbuf_release(&msg);
>         rollback_lock_file(&lock);
> +       clear_unpack_trees_porcelain(&unpack_tree_opts);
>         while (nr)
>                 free((void *)desc[--nr].buffer);
>         return ret;
> --
> 2.26.2