git/tree-diff.c
Jeff King 5b442c4f27 tree-diff: catch integer overflow in combine_diff_path allocation
A combine_diff_path struct has two "flex" members allocated
alongside the struct: a string to hold the pathname, and an
array of parent pointers. We use an "int" to compute this,
meaning we may easily overflow it if the pathname is
extremely long.

We can fix this by using size_t, and checking for overflow
with the st_add helper.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-02-19 09:40:37 -08:00

708 lines
18 KiB
C

/*
* Helper functions for tree diff generation
*/
#include "cache.h"
#include "diff.h"
#include "diffcore.h"
#include "tree.h"
/*
* internal mode marker, saying a tree entry != entry of tp[imin]
* (see ll_diff_tree_paths for what it means there)
*
* we will update/use/emit entry for diff only with it unset.
*/
#define S_IFXMIN_NEQ S_DIFFTREE_IFXMIN_NEQ
static struct combine_diff_path *ll_diff_tree_paths(
struct combine_diff_path *p, const unsigned char *sha1,
const unsigned char **parents_sha1, int nparent,
struct strbuf *base, struct diff_options *opt);
static int ll_diff_tree_sha1(const unsigned char *old, const unsigned char *new,
struct strbuf *base, struct diff_options *opt);
/*
* Compare two tree entries, taking into account only path/S_ISDIR(mode),
* but not their sha1's.
*
* NOTE files and directories *always* compare differently, even when having
* the same name - thanks to base_name_compare().
*
* NOTE empty (=invalid) descriptor(s) take part in comparison as +infty,
* so that they sort *after* valid tree entries.
*
* Due to this convention, if trees are scanned in sorted order, all
* non-empty descriptors will be processed first.
*/
static int tree_entry_pathcmp(struct tree_desc *t1, struct tree_desc *t2)
{
struct name_entry *e1, *e2;
int cmp;
/* empty descriptors sort after valid tree entries */
if (!t1->size)
return t2->size ? 1 : 0;
else if (!t2->size)
return -1;
e1 = &t1->entry;
e2 = &t2->entry;
cmp = base_name_compare(e1->path, tree_entry_len(e1), e1->mode,
e2->path, tree_entry_len(e2), e2->mode);
return cmp;
}
/*
* convert path -> opt->diff_*() callbacks
*
* emits diff to first parent only, and tells diff tree-walker that we are done
* with p and it can be freed.
*/
static int emit_diff_first_parent_only(struct diff_options *opt, struct combine_diff_path *p)
{
struct combine_diff_parent *p0 = &p->parent[0];
if (p->mode && p0->mode) {
opt->change(opt, p0->mode, p->mode, p0->oid.hash, p->oid.hash,
1, 1, p->path, 0, 0);
}
else {
const unsigned char *sha1;
unsigned int mode;
int addremove;
if (p->mode) {
addremove = '+';
sha1 = p->oid.hash;
mode = p->mode;
} else {
addremove = '-';
sha1 = p0->oid.hash;
mode = p0->mode;
}
opt->add_remove(opt, addremove, mode, sha1, 1, p->path, 0);
}
return 0; /* we are done with p */
}
/*
* Make a new combine_diff_path from path/mode/sha1
* and append it to paths list tail.
*
* Memory for created elements could be reused:
*
* - if last->next == NULL, the memory is allocated;
*
* - if last->next != NULL, it is assumed that p=last->next was returned
* earlier by this function, and p->next was *not* modified.
* The memory is then reused from p.
*
* so for clients,
*
* - if you do need to keep the element
*
* p = path_appendnew(p, ...);
* process(p);
* p->next = NULL;
*
* - if you don't need to keep the element after processing
*
* pprev = p;
* p = path_appendnew(p, ...);
* process(p);
* p = pprev;
* ; don't forget to free tail->next in the end
*
* p->parent[] remains uninitialized.
*/
static struct combine_diff_path *path_appendnew(struct combine_diff_path *last,
int nparent, const struct strbuf *base, const char *path, int pathlen,
unsigned mode, const unsigned char *sha1)
{
struct combine_diff_path *p;
size_t len = st_add(base->len, pathlen);
size_t alloclen = combine_diff_path_size(nparent, len);
/* if last->next is !NULL - it is a pre-allocated memory, we can reuse */
p = last->next;
if (p && (alloclen > (intptr_t)p->next)) {
free(p);
p = NULL;
}
if (!p) {
p = xmalloc(alloclen);
/*
* until we go to it next round, .next holds how many bytes we
* allocated (for faster realloc - we don't need copying old data).
*/
p->next = (struct combine_diff_path *)(intptr_t)alloclen;
}
last->next = p;
p->path = (char *)&(p->parent[nparent]);
memcpy(p->path, base->buf, base->len);
memcpy(p->path + base->len, path, pathlen);
p->path[len] = 0;
p->mode = mode;
hashcpy(p->oid.hash, sha1 ? sha1 : null_sha1);
return p;
}
/*
* new path should be added to combine diff
*
* 3 cases on how/when it should be called and behaves:
*
* t, !tp -> path added, all parents lack it
* !t, tp -> path removed from all parents
* t, tp -> path modified/added
* (M for tp[i]=tp[imin], A otherwise)
*/
static struct combine_diff_path *emit_path(struct combine_diff_path *p,
struct strbuf *base, struct diff_options *opt, int nparent,
struct tree_desc *t, struct tree_desc *tp,
int imin)
{
unsigned mode;
const char *path;
const unsigned char *sha1;
int pathlen;
int old_baselen = base->len;
int i, isdir, recurse = 0, emitthis = 1;
/* at least something has to be valid */
assert(t || tp);
if (t) {
/* path present in resulting tree */
sha1 = tree_entry_extract(t, &path, &mode);
pathlen = tree_entry_len(&t->entry);
isdir = S_ISDIR(mode);
} else {
/*
* a path was removed - take path from imin parent. Also take
* mode from that parent, to decide on recursion(1).
*
* 1) all modes for tp[i]=tp[imin] should be the same wrt
* S_ISDIR, thanks to base_name_compare().
*/
tree_entry_extract(&tp[imin], &path, &mode);
pathlen = tree_entry_len(&tp[imin].entry);
isdir = S_ISDIR(mode);
sha1 = NULL;
mode = 0;
}
if (DIFF_OPT_TST(opt, RECURSIVE) && isdir) {
recurse = 1;
emitthis = DIFF_OPT_TST(opt, TREE_IN_RECURSIVE);
}
if (emitthis) {
int keep;
struct combine_diff_path *pprev = p;
p = path_appendnew(p, nparent, base, path, pathlen, mode, sha1);
for (i = 0; i < nparent; ++i) {
/*
* tp[i] is valid, if present and if tp[i]==tp[imin] -
* otherwise, we should ignore it.
*/
int tpi_valid = tp && !(tp[i].entry.mode & S_IFXMIN_NEQ);
const unsigned char *sha1_i;
unsigned mode_i;
p->parent[i].status =
!t ? DIFF_STATUS_DELETED :
tpi_valid ?
DIFF_STATUS_MODIFIED :
DIFF_STATUS_ADDED;
if (tpi_valid) {
sha1_i = tp[i].entry.sha1;
mode_i = tp[i].entry.mode;
}
else {
sha1_i = NULL;
mode_i = 0;
}
p->parent[i].mode = mode_i;
hashcpy(p->parent[i].oid.hash, sha1_i ? sha1_i : null_sha1);
}
keep = 1;
if (opt->pathchange)
keep = opt->pathchange(opt, p);
/*
* If a path was filtered or consumed - we don't need to add it
* to the list and can reuse its memory, leaving it as
* pre-allocated element on the tail.
*
* On the other hand, if path needs to be kept, we need to
* correct its .next to NULL, as it was pre-initialized to how
* much memory was allocated.
*
* see path_appendnew() for details.
*/
if (!keep)
p = pprev;
else
p->next = NULL;
}
if (recurse) {
const unsigned char **parents_sha1;
parents_sha1 = xalloca(nparent * sizeof(parents_sha1[0]));
for (i = 0; i < nparent; ++i) {
/* same rule as in emitthis */
int tpi_valid = tp && !(tp[i].entry.mode & S_IFXMIN_NEQ);
parents_sha1[i] = tpi_valid ? tp[i].entry.sha1
: NULL;
}
strbuf_add(base, path, pathlen);
strbuf_addch(base, '/');
p = ll_diff_tree_paths(p, sha1, parents_sha1, nparent, base, opt);
xalloca_free(parents_sha1);
}
strbuf_setlen(base, old_baselen);
return p;
}
static void skip_uninteresting(struct tree_desc *t, struct strbuf *base,
struct diff_options *opt)
{
enum interesting match;
while (t->size) {
match = tree_entry_interesting(&t->entry, base, 0, &opt->pathspec);
if (match) {
if (match == all_entries_not_interesting)
t->size = 0;
break;
}
update_tree_entry(t);
}
}
/*
* generate paths for combined diff D(sha1,parents_sha1[])
*
* Resulting paths are appended to combine_diff_path linked list, and also, are
* emitted on the go via opt->pathchange() callback, so it is possible to
* process the result as batch or incrementally.
*
* The paths are generated scanning new tree and all parents trees
* simultaneously, similarly to what diff_tree() was doing for 2 trees.
* The theory behind such scan is as follows:
*
*
* D(T,P1...Pn) calculation scheme
* -------------------------------
*
* D(T,P1...Pn) = D(T,P1) ^ ... ^ D(T,Pn) (regarding resulting paths set)
*
* D(T,Pj) - diff between T..Pj
* D(T,P1...Pn) - combined diff from T to parents P1,...,Pn
*
*
* We start from all trees, which are sorted, and compare their entries in
* lock-step:
*
* T P1 Pn
* - - -
* |t| |p1| |pn|
* |-| |--| ... |--| imin = argmin(p1...pn)
* | | | | | |
* |-| |--| |--|
* |.| |. | |. |
* . . .
* . . .
*
* at any time there could be 3 cases:
*
* 1) t < p[imin];
* 2) t > p[imin];
* 3) t = p[imin].
*
* Schematic deduction of what every case means, and what to do, follows:
*
* 1) t < p[imin] -> ∀j t ∉ Pj -> "+t" ∈ D(T,Pj) -> D += "+t"; t↓
*
* 2) t > p[imin]
*
* 2.1) ∃j: pj > p[imin] -> "-p[imin]" ∉ D(T,Pj) -> D += ø; ∀ pi=p[imin] pi↓
* 2.2) ∀i pi = p[imin] -> pi ∉ T -> "-pi" ∈ D(T,Pi) -> D += "-p[imin]"; ∀i pi↓
*
* 3) t = p[imin]
*
* 3.1) ∃j: pj > p[imin] -> "+t" ∈ D(T,Pj) -> only pi=p[imin] remains to investigate
* 3.2) pi = p[imin] -> investigate δ(t,pi)
* |
* |
* v
*
* 3.1+3.2) looking at δ(t,pi) ∀i: pi=p[imin] - if all != ø ->
*
* ⎧δ(t,pi) - if pi=p[imin]
* -> D += ⎨
* ⎩"+t" - if pi>p[imin]
*
*
* in any case t↓ ∀ pi=p[imin] pi↓
*
*
* ~~~~~~~~
*
* NOTE
*
* Usual diff D(A,B) is by definition the same as combined diff D(A,[B]),
* so this diff paths generator can, and is used, for plain diffs
* generation too.
*
* Please keep attention to the common D(A,[B]) case when working on the
* code, in order not to slow it down.
*
* NOTE
* nparent must be > 0.
*/
/* ∀ pi=p[imin] pi↓ */
static inline void update_tp_entries(struct tree_desc *tp, int nparent)
{
int i;
for (i = 0; i < nparent; ++i)
if (!(tp[i].entry.mode & S_IFXMIN_NEQ))
update_tree_entry(&tp[i]);
}
static struct combine_diff_path *ll_diff_tree_paths(
struct combine_diff_path *p, const unsigned char *sha1,
const unsigned char **parents_sha1, int nparent,
struct strbuf *base, struct diff_options *opt)
{
struct tree_desc t, *tp;
void *ttree, **tptree;
int i;
tp = xalloca(nparent * sizeof(tp[0]));
tptree = xalloca(nparent * sizeof(tptree[0]));
/*
* load parents first, as they are probably already cached.
*
* ( log_tree_diff() parses commit->parent before calling here via
* diff_tree_sha1(parent, commit) )
*/
for (i = 0; i < nparent; ++i)
tptree[i] = fill_tree_descriptor(&tp[i], parents_sha1[i]);
ttree = fill_tree_descriptor(&t, sha1);
/* Enable recursion indefinitely */
opt->pathspec.recursive = DIFF_OPT_TST(opt, RECURSIVE);
for (;;) {
int imin, cmp;
if (diff_can_quit_early(opt))
break;
if (opt->pathspec.nr) {
skip_uninteresting(&t, base, opt);
for (i = 0; i < nparent; i++)
skip_uninteresting(&tp[i], base, opt);
}
/* comparing is finished when all trees are done */
if (!t.size) {
int done = 1;
for (i = 0; i < nparent; ++i)
if (tp[i].size) {
done = 0;
break;
}
if (done)
break;
}
/*
* lookup imin = argmin(p1...pn),
* mark entries whether they =p[imin] along the way
*/
imin = 0;
tp[0].entry.mode &= ~S_IFXMIN_NEQ;
for (i = 1; i < nparent; ++i) {
cmp = tree_entry_pathcmp(&tp[i], &tp[imin]);
if (cmp < 0) {
imin = i;
tp[i].entry.mode &= ~S_IFXMIN_NEQ;
}
else if (cmp == 0) {
tp[i].entry.mode &= ~S_IFXMIN_NEQ;
}
else {
tp[i].entry.mode |= S_IFXMIN_NEQ;
}
}
/* fixup markings for entries before imin */
for (i = 0; i < imin; ++i)
tp[i].entry.mode |= S_IFXMIN_NEQ; /* pi > p[imin] */
/* compare t vs p[imin] */
cmp = tree_entry_pathcmp(&t, &tp[imin]);
/* t = p[imin] */
if (cmp == 0) {
/* are either pi > p[imin] or diff(t,pi) != ø ? */
if (!DIFF_OPT_TST(opt, FIND_COPIES_HARDER)) {
for (i = 0; i < nparent; ++i) {
/* p[i] > p[imin] */
if (tp[i].entry.mode & S_IFXMIN_NEQ)
continue;
/* diff(t,pi) != ø */
if (hashcmp(t.entry.sha1, tp[i].entry.sha1) ||
(t.entry.mode != tp[i].entry.mode))
continue;
goto skip_emit_t_tp;
}
}
/* D += {δ(t,pi) if pi=p[imin]; "+a" if pi > p[imin]} */
p = emit_path(p, base, opt, nparent,
&t, tp, imin);
skip_emit_t_tp:
/* t↓, ∀ pi=p[imin] pi↓ */
update_tree_entry(&t);
update_tp_entries(tp, nparent);
}
/* t < p[imin] */
else if (cmp < 0) {
/* D += "+t" */
p = emit_path(p, base, opt, nparent,
&t, /*tp=*/NULL, -1);
/* t↓ */
update_tree_entry(&t);
}
/* t > p[imin] */
else {
/* ∀i pi=p[imin] -> D += "-p[imin]" */
if (!DIFF_OPT_TST(opt, FIND_COPIES_HARDER)) {
for (i = 0; i < nparent; ++i)
if (tp[i].entry.mode & S_IFXMIN_NEQ)
goto skip_emit_tp;
}
p = emit_path(p, base, opt, nparent,
/*t=*/NULL, tp, imin);
skip_emit_tp:
/* ∀ pi=p[imin] pi↓ */
update_tp_entries(tp, nparent);
}
}
free(ttree);
for (i = nparent-1; i >= 0; i--)
free(tptree[i]);
xalloca_free(tptree);
xalloca_free(tp);
return p;
}
struct combine_diff_path *diff_tree_paths(
struct combine_diff_path *p, const unsigned char *sha1,
const unsigned char **parents_sha1, int nparent,
struct strbuf *base, struct diff_options *opt)
{
p = ll_diff_tree_paths(p, sha1, parents_sha1, nparent, base, opt);
/*
* free pre-allocated last element, if any
* (see path_appendnew() for details about why)
*/
if (p->next) {
free(p->next);
p->next = NULL;
}
return p;
}
/*
* Does it look like the resulting diff might be due to a rename?
* - single entry
* - not a valid previous file
*/
static inline int diff_might_be_rename(void)
{
return diff_queued_diff.nr == 1 &&
!DIFF_FILE_VALID(diff_queued_diff.queue[0]->one);
}
static void try_to_follow_renames(const unsigned char *old, const unsigned char *new, struct strbuf *base, struct diff_options *opt)
{
struct diff_options diff_opts;
struct diff_queue_struct *q = &diff_queued_diff;
struct diff_filepair *choice;
int i;
/*
* follow-rename code is very specific, we need exactly one
* path. Magic that matches more than one path is not
* supported.
*/
GUARD_PATHSPEC(&opt->pathspec, PATHSPEC_FROMTOP | PATHSPEC_LITERAL);
#if 0
/*
* We should reject wildcards as well. Unfortunately we
* haven't got a reliable way to detect that 'foo\*bar' in
* fact has no wildcards. nowildcard_len is merely a hint for
* optimization. Let it slip for now until wildmatch is taught
* about dry-run mode and returns wildcard info.
*/
if (opt->pathspec.has_wildcard)
die("BUG:%s:%d: wildcards are not supported",
__FILE__, __LINE__);
#endif
/* Remove the file creation entry from the diff queue, and remember it */
choice = q->queue[0];
q->nr = 0;
diff_setup(&diff_opts);
DIFF_OPT_SET(&diff_opts, RECURSIVE);
DIFF_OPT_SET(&diff_opts, FIND_COPIES_HARDER);
diff_opts.output_format = DIFF_FORMAT_NO_OUTPUT;
diff_opts.single_follow = opt->pathspec.items[0].match;
diff_opts.break_opt = opt->break_opt;
diff_opts.rename_score = opt->rename_score;
diff_setup_done(&diff_opts);
ll_diff_tree_sha1(old, new, base, &diff_opts);
diffcore_std(&diff_opts);
free_pathspec(&diff_opts.pathspec);
/* Go through the new set of filepairing, and see if we find a more interesting one */
opt->found_follow = 0;
for (i = 0; i < q->nr; i++) {
struct diff_filepair *p = q->queue[i];
/*
* Found a source? Not only do we use that for the new
* diff_queued_diff, we will also use that as the path in
* the future!
*/
if ((p->status == 'R' || p->status == 'C') &&
!strcmp(p->two->path, opt->pathspec.items[0].match)) {
const char *path[2];
/* Switch the file-pairs around */
q->queue[i] = choice;
choice = p;
/* Update the path we use from now on.. */
path[0] = p->one->path;
path[1] = NULL;
free_pathspec(&opt->pathspec);
parse_pathspec(&opt->pathspec,
PATHSPEC_ALL_MAGIC & ~PATHSPEC_LITERAL,
PATHSPEC_LITERAL_PATH, "", path);
/*
* The caller expects us to return a set of vanilla
* filepairs to let a later call to diffcore_std()
* it makes to sort the renames out (among other
* things), but we already have found renames
* ourselves; signal diffcore_std() not to muck with
* rename information.
*/
opt->found_follow = 1;
break;
}
}
/*
* Then, discard all the non-relevant file pairs...
*/
for (i = 0; i < q->nr; i++) {
struct diff_filepair *p = q->queue[i];
diff_free_filepair(p);
}
/*
* .. and re-instate the one we want (which might be either the
* original one, or the rename/copy we found)
*/
q->queue[0] = choice;
q->nr = 1;
}
static int ll_diff_tree_sha1(const unsigned char *old, const unsigned char *new,
struct strbuf *base, struct diff_options *opt)
{
struct combine_diff_path phead, *p;
pathchange_fn_t pathchange_old = opt->pathchange;
phead.next = NULL;
opt->pathchange = emit_diff_first_parent_only;
diff_tree_paths(&phead, new, &old, 1, base, opt);
for (p = phead.next; p;) {
struct combine_diff_path *pprev = p;
p = p->next;
free(pprev);
}
opt->pathchange = pathchange_old;
return 0;
}
int diff_tree_sha1(const unsigned char *old, const unsigned char *new, const char *base_str, struct diff_options *opt)
{
struct strbuf base;
int retval;
strbuf_init(&base, PATH_MAX);
strbuf_addstr(&base, base_str);
retval = ll_diff_tree_sha1(old, new, &base, opt);
if (!*base_str && DIFF_OPT_TST(opt, FOLLOW_RENAMES) && diff_might_be_rename())
try_to_follow_renames(old, new, &base, opt);
strbuf_release(&base);
return retval;
}
int diff_root_tree_sha1(const unsigned char *new, const char *base, struct diff_options *opt)
{
return diff_tree_sha1(NULL, new, base, opt);
}