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Merge branch 'vd/fix-unaligned-read-index-v4' into maint-2.38

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The codepath that reads from the index v4 had unaligned memory
accesses, which has been corrected.

* vd/fix-unaligned-read-index-v4:
  read-cache: avoid misaligned reads in index v4
This commit is contained in:
Junio C Hamano 2022-10-25 17:11:32 -07:00
commit 457f863fb4
1 changed files with 42 additions and 19 deletions
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61
read-cache.c
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@ -1873,9 +1873,20 @@ static int read_index_extension(struct index_state *istate,
return 0;
}
/*
* Parses the contents of the cache entry contained within the 'ondisk' buffer
* into a new incore 'cache_entry'.
*
* Note that 'char *ondisk' may not be aligned to a 4-byte address interval in
* index v4, so we cannot cast it to 'struct ondisk_cache_entry *' and access
* its members. Instead, we use the byte offsets of members within the struct to
* identify where 'get_be16()', 'get_be32()', and 'oidread()' (which can all
* read from an unaligned memory buffer) should read from the 'ondisk' buffer
* into the corresponding incore 'cache_entry' members.
*/
static struct cache_entry *create_from_disk(struct mem_pool *ce_mem_pool,
unsigned int version,
struct ondisk_cache_entry *ondisk,
const char *ondisk,
unsigned long *ent_size,
const struct cache_entry *previous_ce)
{
@ -1883,7 +1894,7 @@ static struct cache_entry *create_from_disk(struct mem_pool *ce_mem_pool,
size_t len;
const char *name;
const unsigned hashsz = the_hash_algo->rawsz;
const uint16_t *flagsp = (const uint16_t *)(ondisk->data + hashsz);
const char *flagsp = ondisk + offsetof(struct ondisk_cache_entry, data) + hashsz;
unsigned int flags;
size_t copy_len = 0;
/*
@ -1901,15 +1912,15 @@ static struct cache_entry *create_from_disk(struct mem_pool *ce_mem_pool,
if (flags & CE_EXTENDED) {
int extended_flags;
extended_flags = get_be16(flagsp + 1) << 16;
extended_flags = get_be16(flagsp + sizeof(uint16_t)) << 16;
/* We do not yet understand any bit out of CE_EXTENDED_FLAGS */
if (extended_flags & ~CE_EXTENDED_FLAGS)
die(_("unknown index entry format 0x%08x"), extended_flags);
flags |= extended_flags;
name = (const char *)(flagsp + 2);
name = (const char *)(flagsp + 2 * sizeof(uint16_t));
}
else
name = (const char *)(flagsp + 1);
name = (const char *)(flagsp + sizeof(uint16_t));
if (expand_name_field) {
const unsigned char *cp = (const unsigned char *)name;
@ -1935,20 +1946,32 @@ static struct cache_entry *create_from_disk(struct mem_pool *ce_mem_pool,
ce = mem_pool__ce_alloc(ce_mem_pool, len);
ce->ce_stat_data.sd_ctime.sec = get_be32(&ondisk->ctime.sec);
ce->ce_stat_data.sd_mtime.sec = get_be32(&ondisk->mtime.sec);
ce->ce_stat_data.sd_ctime.nsec = get_be32(&ondisk->ctime.nsec);
ce->ce_stat_data.sd_mtime.nsec = get_be32(&ondisk->mtime.nsec);
ce->ce_stat_data.sd_dev = get_be32(&ondisk->dev);
ce->ce_stat_data.sd_ino = get_be32(&ondisk->ino);
ce->ce_mode = get_be32(&ondisk->mode);
ce->ce_stat_data.sd_uid = get_be32(&ondisk->uid);
ce->ce_stat_data.sd_gid = get_be32(&ondisk->gid);
ce->ce_stat_data.sd_size = get_be32(&ondisk->size);
/*
* NEEDSWORK: using 'offsetof()' is cumbersome and should be replaced
* with something more akin to 'load_bitmap_entries_v1()'s use of
* 'read_be16'/'read_be32'. For consistency with the corresponding
* ondisk entry write function ('copy_cache_entry_to_ondisk()'), this
* should be done at the same time as removing references to
* 'ondisk_cache_entry' there.
*/
ce->ce_stat_data.sd_ctime.sec = get_be32(ondisk + offsetof(struct ondisk_cache_entry, ctime)
+ offsetof(struct cache_time, sec));
ce->ce_stat_data.sd_mtime.sec = get_be32(ondisk + offsetof(struct ondisk_cache_entry, mtime)
+ offsetof(struct cache_time, sec));
ce->ce_stat_data.sd_ctime.nsec = get_be32(ondisk + offsetof(struct ondisk_cache_entry, ctime)
+ offsetof(struct cache_time, nsec));
ce->ce_stat_data.sd_mtime.nsec = get_be32(ondisk + offsetof(struct ondisk_cache_entry, mtime)
+ offsetof(struct cache_time, nsec));
ce->ce_stat_data.sd_dev = get_be32(ondisk + offsetof(struct ondisk_cache_entry, dev));
ce->ce_stat_data.sd_ino = get_be32(ondisk + offsetof(struct ondisk_cache_entry, ino));
ce->ce_mode = get_be32(ondisk + offsetof(struct ondisk_cache_entry, mode));
ce->ce_stat_data.sd_uid = get_be32(ondisk + offsetof(struct ondisk_cache_entry, uid));
ce->ce_stat_data.sd_gid = get_be32(ondisk + offsetof(struct ondisk_cache_entry, gid));
ce->ce_stat_data.sd_size = get_be32(ondisk + offsetof(struct ondisk_cache_entry, size));
ce->ce_flags = flags & ~CE_NAMEMASK;
ce->ce_namelen = len;
ce->index = 0;
oidread(&ce->oid, ondisk->data);
oidread(&ce->oid, (const unsigned char *)ondisk + offsetof(struct ondisk_cache_entry, data));
if (expand_name_field) {
if (copy_len)
@ -2117,12 +2140,12 @@ static unsigned long load_cache_entry_block(struct index_state *istate,
unsigned long src_offset = start_offset;
for (i = offset; i < offset + nr; i++) {
struct ondisk_cache_entry *disk_ce;
struct cache_entry *ce;
unsigned long consumed;
disk_ce = (struct ondisk_cache_entry *)(mmap + src_offset);
ce = create_from_disk(ce_mem_pool, istate->version, disk_ce, &consumed, previous_ce);
ce = create_from_disk(ce_mem_pool, istate->version,
mmap + src_offset,
&consumed, previous_ce);
set_index_entry(istate, i, ce);
src_offset += consumed;