[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(-)