While trying to fix a move based on an uninitialized value (along with a
declaration after the first statement), be0fd57228
(maintenance --unregister: fix uninit'd data use &
-Wdeclaration-after-statement, 2022-11-15) unintentionally introduced a
use-after-free.
The problem arises when `maintenance_unregister()` sees a non-NULL
`config_file` string and thus tries to call
git_configset_get_value_multi() to lookup the corresponding values.
We store the result off, and then call git_configset_clear(), which
frees the pointer that we just stored. We then try to read that
now-freed pointer a few lines below, and there we have our
use-after-free:
$ ./t7900-maintenance.sh -vxi --run=23 --valgrind
[...]
+ git maintenance unregister --config-file ./other
==3048727== Invalid read of size 8
==3048727== at 0x1869CA: maintenance_unregister (gc.c:1590)
==3048727== by 0x188F42: cmd_maintenance (gc.c:2651)
==3048727== by 0x128C62: run_builtin (git.c:466)
==3048727== by 0x12907E: handle_builtin (git.c:721)
==3048727== by 0x1292EC: run_argv (git.c:788)
==3048727== by 0x12988E: cmd_main (git.c:926)
==3048727== by 0x21ED39: main (common-main.c:57)
==3048727== Address 0x4b38bc8 is 24 bytes inside a block of size 64 free'd
==3048727== at 0x484617B: free (vg_replace_malloc.c:872)
==3048727== by 0x2D207E: free_individual_entries (hashmap.c:188)
==3048727== by 0x2D2153: hashmap_clear_ (hashmap.c:207)
==3048727== by 0x270B5C: git_configset_clear (config.c:2375)
==3048727== by 0x1869AC: maintenance_unregister (gc.c:1585)
==3048727== by 0x188F42: cmd_maintenance (gc.c:2651)
==3048727== by 0x128C62: run_builtin (git.c:466)
==3048727== by 0x12907E: handle_builtin (git.c:721)
==3048727== by 0x1292EC: run_argv (git.c:788)
==3048727== by 0x12988E: cmd_main (git.c:926)
==3048727== by 0x21ED39: main (common-main.c:57)
[...]
Resolve this via a partial-revert of be0fd57228. The config_set struct
now gets a zero initialization, which makes free()-ing it a noop even
without calling git_configset_init(). When we do initialize it to a
non-zero value, it is only free()'d after our last read of `list`.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
03744bbdc4