From: Elijah Newren <newren@gmail.com>
To: Jeff King <peff@peff.net>
Cc: Elijah Newren via GitGitGadget <gitgitgadget@gmail.com>,
Git Mailing List <git@vger.kernel.org>
Subject: Re: [PATCH v2 03/10] hashmap: allow re-use after hashmap_free()
Date: Fri, 30 Oct 2020 08:37:42 -0700 [thread overview]
Message-ID: <CABPp-BHRSottxaYO+Ot5tPpNCf4scxmtwBLZicMJ4ChNEhmGHA@mail.gmail.com> (raw)
In-Reply-To: <20201030133518.GC3277724@coredump.intra.peff.net>
On Fri, Oct 30, 2020 at 6:35 AM Jeff King <peff@peff.net> wrote:
>
> On Tue, Oct 13, 2020 at 12:40:43AM +0000, Elijah Newren via GitGitGadget wrote:
>
> > Previously, once map->table had been freed, any calls to hashmap_put(),
> > hashmap_get(), or hashmap_remove() would cause a NULL pointer
> > dereference (since hashmap_free_() also zeros the memory; without that
> > zeroing, calling these functions would cause a use-after-free problem).
> >
> > Modify these functions to check for a NULL table and automatically
> > allocate as needed.
>
> Unsurprisingly, I like this direction. The code looks correct to me,
> though I think you could reduce duplication slightly by checking
> map->table in find_entry_ptr(). That covers both hashmap_get() and
> hashmap_remove(). But I'm happy either way.
>
> > I also thought about creating a HASHMAP_INIT macro to allow initializing
> > hashmaps on the stack without calling hashmap_init(), but virtually all
> > uses of hashmap specify a usecase-specific equals_function which defeats
> > the utility of such a macro.
>
> This part I disagree with. If we did:
>
> #define HASHMAP_INIT(fn, data) = { .cmpfn = cmpfn, cmpfn_data = data }
>
> then many callers could avoid handling the lazy-init themselves. E.g.:
Ah, gotcha. That makes sense to me. Given that 43 out of 47 callers
of hashmap_init use cmpfn_data = NULL, should I shorten it to just one
parameter for the macro, and let the four special cases keep calling
hashmap_init() to specify a non-NULL cmpfn_data?
>
> attr.c | 16 +++-------------
> 1 file changed, 3 insertions(+), 13 deletions(-)
>
> diff --git a/attr.c b/attr.c
> index a826b2ef1f..55a2783f1b 100644
> --- a/attr.c
> +++ b/attr.c
> @@ -57,7 +57,9 @@ static inline void hashmap_unlock(struct attr_hashmap *map)
> * is a singleton object which is shared between threads.
> * Access to this dictionary must be surrounded with a mutex.
> */
> -static struct attr_hashmap g_attr_hashmap;
> +static struct attr_hashmap g_attr_hashmap = {
> + HASHMAP_INIT(attr_hash_entry_cmp, NULL)
> +};
>
> /* The container for objects stored in "struct attr_hashmap" */
> struct attr_hash_entry {
> @@ -80,12 +82,6 @@ static int attr_hash_entry_cmp(const void *unused_cmp_data,
> return (a->keylen != b->keylen) || strncmp(a->key, b->key, a->keylen);
> }
>
> -/* Initialize an 'attr_hashmap' object */
> -static void attr_hashmap_init(struct attr_hashmap *map)
> -{
> - hashmap_init(&map->map, attr_hash_entry_cmp, NULL, 0);
> -}
> -
> /*
> * Retrieve the 'value' stored in a hashmap given the provided 'key'.
> * If there is no matching entry, return NULL.
> @@ -96,9 +92,6 @@ static void *attr_hashmap_get(struct attr_hashmap *map,
> struct attr_hash_entry k;
> struct attr_hash_entry *e;
>
> - if (!map->map.tablesize)
> - attr_hashmap_init(map);
> -
> hashmap_entry_init(&k.ent, memhash(key, keylen));
> k.key = key;
> k.keylen = keylen;
> @@ -114,9 +107,6 @@ static void attr_hashmap_add(struct attr_hashmap *map,
> {
> struct attr_hash_entry *e;
>
> - if (!map->map.tablesize)
> - attr_hashmap_init(map);
> -
> e = xmalloc(sizeof(struct attr_hash_entry));
> hashmap_entry_init(&e->ent, memhash(key, keylen));
> e->key = key;
next prev parent reply other threads:[~2020-10-30 15:37 UTC|newest]
Thread overview: 144+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-21 18:52 [PATCH 0/5] Add struct strmap and associated utility functions Elijah Newren via GitGitGadget
2020-08-21 18:52 ` [PATCH 1/5] hashmap: add usage documentation explaining hashmap_free[_entries]() Elijah Newren via GitGitGadget
2020-08-21 19:22 ` Jeff King
2020-08-21 18:52 ` [PATCH 2/5] strmap: new utility functions Elijah Newren via GitGitGadget
2020-08-21 19:48 ` Jeff King
2020-08-21 18:52 ` [PATCH 3/5] strmap: add more " Elijah Newren via GitGitGadget
2020-08-21 19:58 ` Jeff King
2020-08-21 18:52 ` [PATCH 4/5] strmap: add strdup_strings option Elijah Newren via GitGitGadget
2020-08-21 20:01 ` Jeff King
2020-08-21 20:41 ` Elijah Newren
2020-08-21 21:03 ` Jeff King
2020-08-21 22:25 ` Elijah Newren
2020-08-28 7:08 ` Jeff King
2020-08-28 17:20 ` Elijah Newren
2020-08-21 18:52 ` [PATCH 5/5] strmap: add functions facilitating use as a string->int map Elijah Newren via GitGitGadget
2020-08-21 20:10 ` Jeff King
2020-08-21 20:51 ` Elijah Newren
2020-08-21 21:05 ` Jeff King
2020-08-21 20:16 ` [PATCH 0/5] Add struct strmap and associated utility functions Jeff King
2020-08-21 21:33 ` Elijah Newren
2020-08-21 22:28 ` Elijah Newren
2020-08-28 7:03 ` Jeff King
2020-08-28 15:29 ` Elijah Newren
2020-09-01 9:27 ` Jeff King
2020-10-13 0:40 ` [PATCH v2 00/10] " Elijah Newren via GitGitGadget
2020-10-13 0:40 ` [PATCH v2 01/10] hashmap: add usage documentation explaining hashmap_free[_entries]() Elijah Newren via GitGitGadget
2020-10-30 12:50 ` Jeff King
2020-10-30 19:55 ` Elijah Newren
2020-11-03 16:26 ` Jeff King
2020-11-03 16:48 ` Elijah Newren
2020-10-13 0:40 ` [PATCH v2 02/10] hashmap: adjust spacing to fix argument alignment Elijah Newren via GitGitGadget
2020-10-30 12:51 ` Jeff King
2020-10-13 0:40 ` [PATCH v2 03/10] hashmap: allow re-use after hashmap_free() Elijah Newren via GitGitGadget
2020-10-30 13:35 ` Jeff King
2020-10-30 15:37 ` Elijah Newren [this message]
2020-11-03 16:08 ` Jeff King
2020-11-03 16:16 ` Elijah Newren
2020-10-13 0:40 ` [PATCH v2 04/10] hashmap: introduce a new hashmap_partial_clear() Elijah Newren via GitGitGadget
2020-10-30 13:41 ` Jeff King
2020-10-30 16:03 ` Elijah Newren
2020-11-03 16:10 ` Jeff King
2020-10-13 0:40 ` [PATCH v2 05/10] strmap: new utility functions Elijah Newren via GitGitGadget
2020-10-30 14:12 ` Jeff King
2020-10-30 16:26 ` Elijah Newren
2020-10-13 0:40 ` [PATCH v2 06/10] strmap: add more " Elijah Newren via GitGitGadget
2020-10-30 14:23 ` Jeff King
2020-10-30 16:43 ` Elijah Newren
2020-11-03 16:12 ` Jeff King
2020-10-13 0:40 ` [PATCH v2 07/10] strmap: enable faster clearing and reusing of strmaps Elijah Newren via GitGitGadget
2020-10-30 14:27 ` Jeff King
2020-10-13 0:40 ` [PATCH v2 08/10] strmap: add functions facilitating use as a string->int map Elijah Newren via GitGitGadget
2020-10-30 14:39 ` Jeff King
2020-10-30 17:28 ` Elijah Newren
2020-11-03 16:20 ` Jeff King
2020-11-03 16:46 ` Elijah Newren
2020-10-13 0:40 ` [PATCH v2 09/10] strmap: add a strset sub-type Elijah Newren via GitGitGadget
2020-10-30 14:44 ` Jeff King
2020-10-30 18:02 ` Elijah Newren
2020-10-13 0:40 ` [PATCH v2 10/10] strmap: enable allocations to come from a mem_pool Elijah Newren via GitGitGadget
2020-10-30 14:56 ` Jeff King
2020-10-30 19:31 ` Elijah Newren
2020-11-03 16:24 ` Jeff King
2020-11-02 18:55 ` [PATCH v3 00/13] Add struct strmap and associated utility functions Elijah Newren via GitGitGadget
2020-11-02 18:55 ` [PATCH v3 01/13] hashmap: add usage documentation explaining hashmap_free[_entries]() Elijah Newren via GitGitGadget
2020-11-02 18:55 ` [PATCH v3 02/13] hashmap: adjust spacing to fix argument alignment Elijah Newren via GitGitGadget
2020-11-02 18:55 ` [PATCH v3 03/13] hashmap: allow re-use after hashmap_free() Elijah Newren via GitGitGadget
2020-11-02 18:55 ` [PATCH v3 04/13] hashmap: introduce a new hashmap_partial_clear() Elijah Newren via GitGitGadget
2020-11-02 18:55 ` [PATCH v3 05/13] hashmap: provide deallocation function names Elijah Newren via GitGitGadget
2020-11-02 18:55 ` [PATCH v3 06/13] strmap: new utility functions Elijah Newren via GitGitGadget
2020-11-02 18:55 ` [PATCH v3 07/13] strmap: add more " Elijah Newren via GitGitGadget
2020-11-04 20:13 ` Jeff King
2020-11-04 20:24 ` Elijah Newren
2020-11-02 18:55 ` [PATCH v3 08/13] strmap: enable faster clearing and reusing of strmaps Elijah Newren via GitGitGadget
2020-11-02 18:55 ` [PATCH v3 09/13] strmap: add functions facilitating use as a string->int map Elijah Newren via GitGitGadget
2020-11-04 20:21 ` Jeff King
2020-11-02 18:55 ` [PATCH v3 10/13] strmap: add a strset sub-type Elijah Newren via GitGitGadget
2020-11-04 20:31 ` Jeff King
2020-11-02 18:55 ` [PATCH v3 11/13] strmap: enable allocations to come from a mem_pool Elijah Newren via GitGitGadget
2020-11-02 18:55 ` [PATCH v3 12/13] strmap: take advantage of FLEXPTR_ALLOC_STR when relevant Elijah Newren via GitGitGadget
2020-11-04 20:43 ` Jeff King
2020-11-02 18:55 ` [PATCH v3 13/13] Use new HASHMAP_INIT macro to simplify hashmap initialization Elijah Newren via GitGitGadget
2020-11-04 20:48 ` Jeff King
2020-11-04 20:52 ` [PATCH v3 00/13] Add struct strmap and associated utility functions Jeff King
2020-11-04 22:20 ` Elijah Newren
2020-11-05 0:22 ` [PATCH v4 " Elijah Newren via GitGitGadget
2020-11-05 0:22 ` [PATCH v4 01/13] hashmap: add usage documentation explaining hashmap_free[_entries]() Elijah Newren via GitGitGadget
2020-11-05 0:22 ` [PATCH v4 02/13] hashmap: adjust spacing to fix argument alignment Elijah Newren via GitGitGadget
2020-11-05 0:22 ` [PATCH v4 03/13] hashmap: allow re-use after hashmap_free() Elijah Newren via GitGitGadget
2020-11-05 0:22 ` [PATCH v4 04/13] hashmap: introduce a new hashmap_partial_clear() Elijah Newren via GitGitGadget
2020-11-05 0:22 ` [PATCH v4 05/13] hashmap: provide deallocation function names Elijah Newren via GitGitGadget
2020-11-05 0:22 ` [PATCH v4 06/13] strmap: new utility functions Elijah Newren via GitGitGadget
2020-11-05 0:22 ` [PATCH v4 07/13] strmap: add more " Elijah Newren via GitGitGadget
2020-11-05 0:22 ` [PATCH v4 08/13] strmap: enable faster clearing and reusing of strmaps Elijah Newren via GitGitGadget
2020-11-05 0:22 ` [PATCH v4 09/13] strmap: add functions facilitating use as a string->int map Elijah Newren via GitGitGadget
2020-11-05 0:22 ` [PATCH v4 10/13] strmap: add a strset sub-type Elijah Newren via GitGitGadget
2020-11-05 0:22 ` [PATCH v4 11/13] strmap: enable allocations to come from a mem_pool Elijah Newren via GitGitGadget
2020-11-05 0:22 ` [PATCH v4 12/13] strmap: take advantage of FLEXPTR_ALLOC_STR when relevant Elijah Newren via GitGitGadget
2020-11-05 0:22 ` [PATCH v4 13/13] Use new HASHMAP_INIT macro to simplify hashmap initialization Elijah Newren via GitGitGadget
2020-11-05 13:29 ` [PATCH v4 00/13] Add struct strmap and associated utility functions Jeff King
2020-11-05 20:25 ` Junio C Hamano
2020-11-05 21:17 ` Jeff King
2020-11-05 21:22 ` Elijah Newren
2020-11-05 22:15 ` Junio C Hamano
2020-11-06 0:24 ` [PATCH v5 00/15] " Elijah Newren via GitGitGadget
2020-11-06 0:24 ` [PATCH v5 01/15] hashmap: add usage documentation explaining hashmap_free[_entries]() Elijah Newren via GitGitGadget
2020-11-06 0:24 ` [PATCH v5 02/15] hashmap: adjust spacing to fix argument alignment Elijah Newren via GitGitGadget
2020-11-06 0:24 ` [PATCH v5 03/15] hashmap: allow re-use after hashmap_free() Elijah Newren via GitGitGadget
2020-11-06 0:24 ` [PATCH v5 04/15] hashmap: introduce a new hashmap_partial_clear() Elijah Newren via GitGitGadget
2020-11-06 0:24 ` [PATCH v5 05/15] hashmap: provide deallocation function names Elijah Newren via GitGitGadget
2020-11-06 0:24 ` [PATCH v5 06/15] strmap: new utility functions Elijah Newren via GitGitGadget
2020-11-06 0:24 ` [PATCH v5 07/15] strmap: add more " Elijah Newren via GitGitGadget
2020-11-06 0:24 ` [PATCH v5 08/15] strmap: enable faster clearing and reusing of strmaps Elijah Newren via GitGitGadget
2020-11-06 0:24 ` [PATCH v5 09/15] strmap: add functions facilitating use as a string->int map Elijah Newren via GitGitGadget
2020-11-06 0:24 ` [PATCH v5 10/15] strmap: split create_entry() out of strmap_put() Elijah Newren via GitGitGadget
2020-11-06 0:24 ` [PATCH v5 11/15] strmap: add a strset sub-type Elijah Newren via GitGitGadget
2020-11-06 0:24 ` [PATCH v5 12/15] strmap: enable allocations to come from a mem_pool Elijah Newren via GitGitGadget
2020-11-11 17:33 ` Phillip Wood
2020-11-11 18:49 ` Elijah Newren
2020-11-11 19:01 ` Jeff King
2020-11-11 20:34 ` Chris Torek
2020-11-06 0:24 ` [PATCH v5 13/15] strmap: take advantage of FLEXPTR_ALLOC_STR when relevant Elijah Newren via GitGitGadget
2020-11-06 0:24 ` [PATCH v5 14/15] Use new HASHMAP_INIT macro to simplify hashmap initialization Elijah Newren via GitGitGadget
2020-11-06 0:24 ` [PATCH v5 15/15] shortlog: use strset from strmap.h Elijah Newren via GitGitGadget
2020-11-06 2:00 ` [PATCH v5 00/15] Add struct strmap and associated utility functions Junio C Hamano
2020-11-06 2:42 ` Elijah Newren
2020-11-06 2:48 ` Jeff King
2020-11-06 17:32 ` Junio C Hamano
2020-11-11 20:02 ` [PATCH v6 " Elijah Newren via GitGitGadget
2020-11-11 20:02 ` [PATCH v6 01/15] hashmap: add usage documentation explaining hashmap_free[_entries]() Elijah Newren via GitGitGadget
2020-11-11 20:02 ` [PATCH v6 02/15] hashmap: adjust spacing to fix argument alignment Elijah Newren via GitGitGadget
2020-11-11 20:02 ` [PATCH v6 03/15] hashmap: allow re-use after hashmap_free() Elijah Newren via GitGitGadget
2020-11-11 20:02 ` [PATCH v6 04/15] hashmap: introduce a new hashmap_partial_clear() Elijah Newren via GitGitGadget
2020-11-11 20:02 ` [PATCH v6 05/15] hashmap: provide deallocation function names Elijah Newren via GitGitGadget
2020-11-11 20:02 ` [PATCH v6 06/15] strmap: new utility functions Elijah Newren via GitGitGadget
2020-11-11 20:02 ` [PATCH v6 07/15] strmap: add more " Elijah Newren via GitGitGadget
2020-11-11 20:02 ` [PATCH v6 08/15] strmap: enable faster clearing and reusing of strmaps Elijah Newren via GitGitGadget
2020-11-11 20:02 ` [PATCH v6 09/15] strmap: add functions facilitating use as a string->int map Elijah Newren via GitGitGadget
2020-11-11 20:02 ` [PATCH v6 10/15] strmap: split create_entry() out of strmap_put() Elijah Newren via GitGitGadget
2020-11-11 20:02 ` [PATCH v6 11/15] strmap: add a strset sub-type Elijah Newren via GitGitGadget
2020-11-11 20:02 ` [PATCH v6 12/15] strmap: enable allocations to come from a mem_pool Elijah Newren via GitGitGadget
2020-11-11 20:02 ` [PATCH v6 13/15] strmap: take advantage of FLEXPTR_ALLOC_STR when relevant Elijah Newren via GitGitGadget
2020-11-11 20:02 ` [PATCH v6 14/15] Use new HASHMAP_INIT macro to simplify hashmap initialization Elijah Newren via GitGitGadget
2020-11-11 20:02 ` [PATCH v6 15/15] shortlog: use strset from strmap.h Elijah Newren via GitGitGadget
2020-11-11 20:07 ` [PATCH v6 00/15] Add struct strmap and associated utility functions Jeff King
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