Revision 24557209500e6ed618f04a8795a111a0c491a29c authored by Patrick Steinhardt on 01 December 2022, 14:45:23 UTC, committed by Junio C Hamano on 05 December 2022, 06:14:16 UTC
It is possible to trigger an integer overflow when parsing attribute names that are longer than 2^31 bytes because we assign the result of strlen(3P) to an `int` instead of to a `size_t`. This can lead to an abort in vsnprintf(3P) with the following reproducer: blob=$(perl -e 'print "A " . "B"x2147483648 . "\n"' | git hash-object -w --stdin) git update-index --add --cacheinfo 100644,$blob,.gitattributes git check-attr --all path BUG: strbuf.c:400: your vsnprintf is broken (returned -1) But furthermore, assuming that the attribute name is even longer than that, it can cause us to silently truncate the attribute and thus lead to wrong results. Fix this integer overflow by using a `size_t` instead. This fixes the silent truncation of attribute names, but it only partially fixes the BUG we hit: even though the initial BUG is fixed, we can still hit a BUG when parsing invalid attribute lines via `report_invalid_attr()`. This is due to an underlying design issue in vsnprintf(3P) which only knows to return an `int`, and thus it may always overflow with large inputs. This issue is benign though: the worst that can happen is that the error message is misreported to be either truncated or too long, but due to the buffer being NUL terminated we wouldn't ever do an out-of-bounds read here. Reported-by: Markus Vervier <markus.vervier@x41-dsec.de> Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>
1 parent 8d0d48c
hashmap.c
/*
* Generic implementation of hash-based key value mappings.
*/
#include "cache.h"
#include "hashmap.h"
#define FNV32_BASE ((unsigned int) 0x811c9dc5)
#define FNV32_PRIME ((unsigned int) 0x01000193)
unsigned int strhash(const char *str)
{
unsigned int c, hash = FNV32_BASE;
while ((c = (unsigned char) *str++))
hash = (hash * FNV32_PRIME) ^ c;
return hash;
}
unsigned int strihash(const char *str)
{
unsigned int c, hash = FNV32_BASE;
while ((c = (unsigned char) *str++)) {
if (c >= 'a' && c <= 'z')
c -= 'a' - 'A';
hash = (hash * FNV32_PRIME) ^ c;
}
return hash;
}
unsigned int memhash(const void *buf, size_t len)
{
unsigned int hash = FNV32_BASE;
unsigned char *ucbuf = (unsigned char *) buf;
while (len--) {
unsigned int c = *ucbuf++;
hash = (hash * FNV32_PRIME) ^ c;
}
return hash;
}
unsigned int memihash(const void *buf, size_t len)
{
unsigned int hash = FNV32_BASE;
unsigned char *ucbuf = (unsigned char *) buf;
while (len--) {
unsigned int c = *ucbuf++;
if (c >= 'a' && c <= 'z')
c -= 'a' - 'A';
hash = (hash * FNV32_PRIME) ^ c;
}
return hash;
}
/*
* Incorporate another chunk of data into a memihash
* computation.
*/
unsigned int memihash_cont(unsigned int hash_seed, const void *buf, size_t len)
{
unsigned int hash = hash_seed;
unsigned char *ucbuf = (unsigned char *) buf;
while (len--) {
unsigned int c = *ucbuf++;
if (c >= 'a' && c <= 'z')
c -= 'a' - 'A';
hash = (hash * FNV32_PRIME) ^ c;
}
return hash;
}
#define HASHMAP_INITIAL_SIZE 64
/* grow / shrink by 2^2 */
#define HASHMAP_RESIZE_BITS 2
/* load factor in percent */
#define HASHMAP_LOAD_FACTOR 80
static void alloc_table(struct hashmap *map, unsigned int size)
{
map->tablesize = size;
map->table = xcalloc(size, sizeof(struct hashmap_entry *));
/* calculate resize thresholds for new size */
map->grow_at = (unsigned int) ((uint64_t) size * HASHMAP_LOAD_FACTOR / 100);
if (size <= HASHMAP_INITIAL_SIZE)
map->shrink_at = 0;
else
/*
* The shrink-threshold must be slightly smaller than
* (grow-threshold / resize-factor) to prevent erratic resizing,
* thus we divide by (resize-factor + 1).
*/
map->shrink_at = map->grow_at / ((1 << HASHMAP_RESIZE_BITS) + 1);
}
static inline int entry_equals(const struct hashmap *map,
const struct hashmap_entry *e1,
const struct hashmap_entry *e2,
const void *keydata)
{
return (e1 == e2) ||
(e1->hash == e2->hash &&
!map->cmpfn(map->cmpfn_data, e1, e2, keydata));
}
static inline unsigned int bucket(const struct hashmap *map,
const struct hashmap_entry *key)
{
return key->hash & (map->tablesize - 1);
}
int hashmap_bucket(const struct hashmap *map, unsigned int hash)
{
return hash & (map->tablesize - 1);
}
static void rehash(struct hashmap *map, unsigned int newsize)
{
/* map->table MUST NOT be NULL when this function is called */
unsigned int i, oldsize = map->tablesize;
struct hashmap_entry **oldtable = map->table;
alloc_table(map, newsize);
for (i = 0; i < oldsize; i++) {
struct hashmap_entry *e = oldtable[i];
while (e) {
struct hashmap_entry *next = e->next;
unsigned int b = bucket(map, e);
e->next = map->table[b];
map->table[b] = e;
e = next;
}
}
free(oldtable);
}
static inline struct hashmap_entry **find_entry_ptr(const struct hashmap *map,
const struct hashmap_entry *key, const void *keydata)
{
/* map->table MUST NOT be NULL when this function is called */
struct hashmap_entry **e = &map->table[bucket(map, key)];
while (*e && !entry_equals(map, *e, key, keydata))
e = &(*e)->next;
return e;
}
static int always_equal(const void *unused_cmp_data,
const struct hashmap_entry *unused1,
const struct hashmap_entry *unused2,
const void *unused_keydata)
{
return 0;
}
void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function,
const void *cmpfn_data, size_t initial_size)
{
unsigned int size = HASHMAP_INITIAL_SIZE;
memset(map, 0, sizeof(*map));
map->cmpfn = equals_function ? equals_function : always_equal;
map->cmpfn_data = cmpfn_data;
/* calculate initial table size and allocate the table */
initial_size = (unsigned int) ((uint64_t) initial_size * 100
/ HASHMAP_LOAD_FACTOR);
while (initial_size > size)
size <<= HASHMAP_RESIZE_BITS;
alloc_table(map, size);
/*
* Keep track of the number of items in the map and
* allow the map to automatically grow as necessary.
*/
map->do_count_items = 1;
}
static void free_individual_entries(struct hashmap *map, ssize_t entry_offset)
{
struct hashmap_iter iter;
struct hashmap_entry *e;
hashmap_iter_init(map, &iter);
while ((e = hashmap_iter_next(&iter)))
/*
* like container_of, but using caller-calculated
* offset (caller being hashmap_clear_and_free)
*/
free((char *)e - entry_offset);
}
void hashmap_partial_clear_(struct hashmap *map, ssize_t entry_offset)
{
if (!map || !map->table)
return;
if (entry_offset >= 0) /* called by hashmap_clear_entries */
free_individual_entries(map, entry_offset);
memset(map->table, 0, map->tablesize * sizeof(struct hashmap_entry *));
map->shrink_at = 0;
map->private_size = 0;
}
void hashmap_clear_(struct hashmap *map, ssize_t entry_offset)
{
if (!map || !map->table)
return;
if (entry_offset >= 0) /* called by hashmap_clear_and_free */
free_individual_entries(map, entry_offset);
free(map->table);
memset(map, 0, sizeof(*map));
}
struct hashmap_entry *hashmap_get(const struct hashmap *map,
const struct hashmap_entry *key,
const void *keydata)
{
if (!map->table)
return NULL;
return *find_entry_ptr(map, key, keydata);
}
struct hashmap_entry *hashmap_get_next(const struct hashmap *map,
const struct hashmap_entry *entry)
{
struct hashmap_entry *e = entry->next;
for (; e; e = e->next)
if (entry_equals(map, entry, e, NULL))
return e;
return NULL;
}
void hashmap_add(struct hashmap *map, struct hashmap_entry *entry)
{
unsigned int b;
if (!map->table)
alloc_table(map, HASHMAP_INITIAL_SIZE);
b = bucket(map, entry);
/* add entry */
entry->next = map->table[b];
map->table[b] = entry;
/* fix size and rehash if appropriate */
if (map->do_count_items) {
map->private_size++;
if (map->private_size > map->grow_at)
rehash(map, map->tablesize << HASHMAP_RESIZE_BITS);
}
}
struct hashmap_entry *hashmap_remove(struct hashmap *map,
const struct hashmap_entry *key,
const void *keydata)
{
struct hashmap_entry *old;
struct hashmap_entry **e;
if (!map->table)
return NULL;
e = find_entry_ptr(map, key, keydata);
if (!*e)
return NULL;
/* remove existing entry */
old = *e;
*e = old->next;
old->next = NULL;
/* fix size and rehash if appropriate */
if (map->do_count_items) {
map->private_size--;
if (map->private_size < map->shrink_at)
rehash(map, map->tablesize >> HASHMAP_RESIZE_BITS);
}
return old;
}
struct hashmap_entry *hashmap_put(struct hashmap *map,
struct hashmap_entry *entry)
{
struct hashmap_entry *old = hashmap_remove(map, entry, NULL);
hashmap_add(map, entry);
return old;
}
void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter)
{
iter->map = map;
iter->tablepos = 0;
iter->next = NULL;
}
struct hashmap_entry *hashmap_iter_next(struct hashmap_iter *iter)
{
struct hashmap_entry *current = iter->next;
for (;;) {
if (current) {
iter->next = current->next;
return current;
}
if (iter->tablepos >= iter->map->tablesize)
return NULL;
current = iter->map->table[iter->tablepos++];
}
}
struct pool_entry {
struct hashmap_entry ent;
size_t len;
unsigned char data[FLEX_ARRAY];
};
static int pool_entry_cmp(const void *unused_cmp_data,
const struct hashmap_entry *eptr,
const struct hashmap_entry *entry_or_key,
const void *keydata)
{
const struct pool_entry *e1, *e2;
e1 = container_of(eptr, const struct pool_entry, ent);
e2 = container_of(entry_or_key, const struct pool_entry, ent);
return e1->data != keydata &&
(e1->len != e2->len || memcmp(e1->data, keydata, e1->len));
}
const void *memintern(const void *data, size_t len)
{
static struct hashmap map;
struct pool_entry key, *e;
/* initialize string pool hashmap */
if (!map.tablesize)
hashmap_init(&map, pool_entry_cmp, NULL, 0);
/* lookup interned string in pool */
hashmap_entry_init(&key.ent, memhash(data, len));
key.len = len;
e = hashmap_get_entry(&map, &key, ent, data);
if (!e) {
/* not found: create it */
FLEX_ALLOC_MEM(e, data, data, len);
hashmap_entry_init(&e->ent, key.ent.hash);
e->len = len;
hashmap_add(&map, &e->ent);
}
return e->data;
}
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