RE: [PATCH] reflog: close leak of reflog expire entry

> -----Original Message-----
> From: Jeff King <peff@peff.net>
> Sent: Wednesday, July 9, 2025 3:37 PM
> To: Keller, Jacob E <jacob.e.keller@intel.com>
> Cc: git@vger.kernel.org; Junio C Hamano <gitster@pobox.com>; Jacob Keller
> <jacob.keller@gmail.com>
> Subject: Re: [PATCH] reflog: close leak of reflog expire entry
> 
> On Wed, Jul 09, 2025 at 02:49:14PM -0700, Jacob Keller wrote:
> 
> > find_cfg_ent() allocates a struct reflog_expire_entry_option via
> > FLEX_ALLOC_MEM and returns its pointer to reflog_expire_config(). The
> > function exits without freeing the memory:
> >
> > Direct leak of 39 byte(s) in 1 object(s) allocated from:
> >     #0 0x7ff975ee6883 in calloc (/lib64/libasan.so.8+0xe6883)
> >     #1 0x0000010edada in xcalloc ../wrapper.c:154
> >     #2 0x000000df0898 in find_cfg_ent ../reflog.c:28
> >     #3 0x000000df0898 in reflog_expire_config ../reflog.c:70
> >     #4 0x00000095c451 in configset_iter ../config.c:2116
> >     #5 0x0000006d29e7 in git_config ../config.h:724
> >     #6 0x0000006d29e7 in cmd_reflog_expire ../builtin/reflog.c:205
> >     #7 0x0000006d504c in cmd_reflog ../builtin/reflog.c:419
> >     #8 0x0000007e4054 in run_builtin ../git.c:480
> >     #9 0x0000007e4054 in handle_builtin ../git.c:746
> >     #10 0x0000007e8a35 in run_argv ../git.c:813
> >     #11 0x0000007e8a35 in cmd_main ../git.c:953
> >     #12 0x000000441e8f in main ../common-main.c:9
> >     #13 0x7ff9754115f4 in __libc_start_call_main (/lib64/libc.so.6+0x35f4)
> >     #14 0x7ff9754116a7 in __libc_start_main@@GLIBC_2.34
> (/lib64/libc.so.6+0x36a7)
> >     #15 0x000000444184 in _start (/home/jekeller/libexec/git-
> core/git+0x444184)
> >
> > Close this leak by freeing the entry pointer on exit of the
> > reflog_expire_config() function. This frees both the entry structure and
> > its embedded pattern array thanks to the use of FLEX_ALLOC_MEM.
> 
> Hmm, this can't be right, can it? The end of reflog_expire_config()
> looks like this:
> 
>         ent = find_cfg_ent(opts, pattern, pattern_len);
>         if (!ent)
>                 return -1;
>         switch (slot) {
>         case REFLOG_EXPIRE_TOTAL:
>                 ent->expire_total = expire;
>                 break;
>         case REFLOG_EXPIRE_UNREACH:
>                 ent->expire_unreachable = expire;
>                 break;
>         }
>         return 0;
> 
> So if we free(ent), then what was the point of the function? We'd set
> some fields in it and then throw it away?
> 
> And indeed, find_cfg_ent() seems to add the newly allocated entry to the
> list opt->entries list. So by freeing here, we're leaving a dangling
> pointer in that list.
> 
> Probably that list needs to be cleaned up when cmd_reflog_expire()
> finishes?
> 
> -Peff