https://github.com/git/git
Revision a5bb10fd5e74101e7c07da93e7c32bbe60f6173a authored by Taylor Blau on 06 April 2023, 18:07:58 UTC, committed by Johannes Schindelin on 17 April 2023, 19:15:40 UTC
When renaming (or deleting) a section of configuration, Git uses the
function `git_config_copy_or_rename_section_in_file()` to rewrite the
configuration file after applying the rename or deletion to the given
section.
To do this, Git repeatedly calls `fgets()` to read the existing
configuration data into a fixed size buffer.
When the configuration value under `old_name` exceeds the size of the
buffer, we will call `fgets()` an additional time even if there is no
newline in the configuration file, since our read length is capped at
`sizeof(buf)`.
If the first character of the buffer (after zero or more characters
satisfying `isspace()`) is a '[', Git will incorrectly treat it as
beginning a new section when the original section is being removed. In
other words, a configuration value satisfying this criteria can
incorrectly be considered as a new secftion instead of a variable in the
original section.
Avoid this issue by using a variable-width buffer in the form of a
strbuf rather than a fixed-with region on the stack. A couple of small
points worth noting:
- Using a strbuf will cause us to allocate arbitrary sizes to match
the length of each line. In practice, we don't expect any
reasonable configuration files to have lines that long, and a
bandaid will be introduced in a later patch to ensure that this is
the case.
- We are using strbuf_getwholeline() here instead of strbuf_getline()
in order to match `fgets()`'s behavior of leaving the trailing LF
character on the buffer (as well as a trailing NUL).
This could be changed later, but using strbuf_getwholeline() changes
the least about this function's implementation, so it is picked as
the safest path.
- It is temping to want to replace the loop to skip over characters
matching isspace() at the beginning of the buffer with a convenience
function like `strbuf_ltrim()`. But this is the wrong approach for a
couple of reasons:
First, it involves a potentially large and expensive `memmove()`
which we would like to avoid. Second, and more importantly, we also
*do* want to preserve those spaces to avoid changing the output of
other sections.
In all, this patch is a minimal replacement of the fixed-width buffer in
`git_config_copy_or_rename_section_in_file()` to instead use a `struct
strbuf`.
Reported-by: André Baptista <andre@ethiack.com>
Reported-by: Vítor Pinho <vitor@ethiack.com>
Helped-by: Patrick Steinhardt <ps@pks.im>
Co-authored-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
1 parent 2919821
Tip revision: a5bb10fd5e74101e7c07da93e7c32bbe60f6173a authored by Taylor Blau on 06 April 2023, 18:07:58 UTC
config: avoid fixed-sized buffer when renaming/deleting a section
config: avoid fixed-sized buffer when renaming/deleting a section
Tip revision: a5bb10f
patch-ids.c
#include "cache.h"
#include "diff.h"
#include "commit.h"
#include "sha1-lookup.h"
#include "patch-ids.h"
static int patch_id_defined(struct commit *commit)
{
/* must be 0 or 1 parents */
return !commit->parents || !commit->parents->next;
}
int commit_patch_id(struct commit *commit, struct diff_options *options,
struct object_id *oid, int diff_header_only, int stable)
{
if (!patch_id_defined(commit))
return -1;
if (commit->parents)
diff_tree_oid(&commit->parents->item->object.oid,
&commit->object.oid, "", options);
else
diff_root_tree_oid(&commit->object.oid, "", options);
diffcore_std(options);
return diff_flush_patch_id(options, oid, diff_header_only, stable);
}
/*
* When we cannot load the full patch-id for both commits for whatever
* reason, the function returns -1 (i.e. return error(...)). Despite
* the "neq" in the name of this function, the caller only cares about
* the return value being zero (a and b are equivalent) or non-zero (a
* and b are different), and returning non-zero would keep both in the
* result, even if they actually were equivalent, in order to err on
* the side of safety. The actual value being negative does not have
* any significance; only that it is non-zero matters.
*/
static int patch_id_neq(const void *cmpfn_data,
const struct hashmap_entry *eptr,
const struct hashmap_entry *entry_or_key,
const void *unused_keydata)
{
/* NEEDSWORK: const correctness? */
struct diff_options *opt = (void *)cmpfn_data;
struct patch_id *a, *b;
a = container_of(eptr, struct patch_id, ent);
b = container_of(entry_or_key, struct patch_id, ent);
if (is_null_oid(&a->patch_id) &&
commit_patch_id(a->commit, opt, &a->patch_id, 0, 0))
return error("Could not get patch ID for %s",
oid_to_hex(&a->commit->object.oid));
if (is_null_oid(&b->patch_id) &&
commit_patch_id(b->commit, opt, &b->patch_id, 0, 0))
return error("Could not get patch ID for %s",
oid_to_hex(&b->commit->object.oid));
return !oideq(&a->patch_id, &b->patch_id);
}
int init_patch_ids(struct repository *r, struct patch_ids *ids)
{
memset(ids, 0, sizeof(*ids));
repo_diff_setup(r, &ids->diffopts);
ids->diffopts.detect_rename = 0;
ids->diffopts.flags.recursive = 1;
diff_setup_done(&ids->diffopts);
hashmap_init(&ids->patches, patch_id_neq, &ids->diffopts, 256);
return 0;
}
int free_patch_ids(struct patch_ids *ids)
{
hashmap_clear_and_free(&ids->patches, struct patch_id, ent);
return 0;
}
static int init_patch_id_entry(struct patch_id *patch,
struct commit *commit,
struct patch_ids *ids)
{
struct object_id header_only_patch_id;
patch->commit = commit;
if (commit_patch_id(commit, &ids->diffopts, &header_only_patch_id, 1, 0))
return -1;
hashmap_entry_init(&patch->ent, oidhash(&header_only_patch_id));
return 0;
}
struct patch_id *patch_id_iter_first(struct commit *commit,
struct patch_ids *ids)
{
struct patch_id patch;
if (!patch_id_defined(commit))
return NULL;
memset(&patch, 0, sizeof(patch));
if (init_patch_id_entry(&patch, commit, ids))
return NULL;
return hashmap_get_entry(&ids->patches, &patch, ent, NULL);
}
struct patch_id *patch_id_iter_next(struct patch_id *cur,
struct patch_ids *ids)
{
return hashmap_get_next_entry(&ids->patches, cur, ent);
}
int has_commit_patch_id(struct commit *commit,
struct patch_ids *ids)
{
return !!patch_id_iter_first(commit, ids);
}
struct patch_id *add_commit_patch_id(struct commit *commit,
struct patch_ids *ids)
{
struct patch_id *key;
if (!patch_id_defined(commit))
return NULL;
key = xcalloc(1, sizeof(*key));
if (init_patch_id_entry(key, commit, ids)) {
free(key);
return NULL;
}
hashmap_add(&ids->patches, &key->ent);
return key;
}
Computing file changes ...
