This patch series addresses a problem where `git diff` is called using `-G` or `-S --pickaxe-regex` on new-born files that are configured without user diff drivers, and that hence get mmap()ed into memory.
The problem with that: mmap()ed memory is *not* NUL-terminated, yet the pickaxe code calls regexec() on it just the same. This problem has been reported by my colleague Chris Sidi. We solve this by introducing a helper, regexec_buf(), that takes a pointer and a length instead of a NUL-terminated string. This helper then uses REG_STARTEND where available, and falls back to allocating and constructing a NUL-terminated string. Given the wide-spread support for REG_STARTEND (Linux has it, MacOSX has it, Git for Windows has it because it uses compat/regex/ that has it), I think this is a fair trade-off. Changes since v1: - completely revamped the approach: now we no longer force-append a NUL whenever mmap()ing buffers for use by the diff machinery, but we fix things at the regexec() level. Johannes Schindelin (3): Demonstrate a problem: our pickaxe code assumes NUL-terminated buffers Introduce a function to run regexec() on non-NUL-terminated buffers Use the newly-introduced regexec_buf() function diff.c | 3 ++- diffcore-pickaxe.c | 18 ++++++++---------- git-compat-util.h | 21 +++++++++++++++++++++ t/t4061-diff-pickaxe.sh | 22 ++++++++++++++++++++++ xdiff-interface.c | 13 ++++--------- 5 files changed, 57 insertions(+), 20 deletions(-) create mode 100755 t/t4061-diff-pickaxe.sh Published-As: https://github.com/dscho/git/releases/tag/mmap-regexec-v2 Fetch-It-Via: git fetch https://github.com/dscho/git mmap-regexec-v2 Interdiff vs v1: diff --git a/diff.c b/diff.c index 32f7f46..526775a 100644 --- a/diff.c +++ b/diff.c @@ -951,7 +951,8 @@ static int find_word_boundaries(mmfile_t *buffer, regex_t *word_regex, { if (word_regex && *begin < buffer->size) { regmatch_t match[1]; - if (!regexec(word_regex, buffer->ptr + *begin, 1, match, 0)) { + if (!regexec_buf(word_regex, buffer->ptr + *begin, + buffer->size - *begin, 1, match, 0)) { char *p = memchr(buffer->ptr + *begin + match[0].rm_so, '\n', match[0].rm_eo - match[0].rm_so); *end = p ? p - buffer->ptr : match[0].rm_eo + *begin; @@ -2826,15 +2827,6 @@ int diff_populate_filespec(struct diff_filespec *s, unsigned int flags) s->data = strbuf_detach(&buf, &size); s->size = size; s->should_free = 1; - } else { - /* data must be NUL-terminated so e.g. for regexec() */ - char *data = xmalloc(s->size + 1); - memcpy(data, s->data, s->size); - data[s->size] = '\0'; - munmap(s->data, s->size); - s->should_munmap = 0; - s->data = data; - s->should_free = 1; } } else { diff --git a/diffcore-pickaxe.c b/diffcore-pickaxe.c index 88820b6..9795ca1 100644 --- a/diffcore-pickaxe.c +++ b/diffcore-pickaxe.c @@ -23,7 +23,6 @@ static void diffgrep_consume(void *priv, char *line, unsigned long len) { struct diffgrep_cb *data = priv; regmatch_t regmatch; - int hold; if (line[0] != '+' && line[0] != '-') return; @@ -33,11 +32,8 @@ static void diffgrep_consume(void *priv, char *line, unsigned long len) * caller early. */ return; - /* Yuck -- line ought to be "const char *"! */ - hold = line[len]; - line[len] = '\0'; - data->hit = !regexec(data->regexp, line + 1, 1, ®match, 0); - line[len] = hold; + data->hit = !regexec_buf(data->regexp, line + 1, len - 1, 1, + ®match, 0); } static int diff_grep(mmfile_t *one, mmfile_t *two, @@ -49,12 +45,12 @@ static int diff_grep(mmfile_t *one, mmfile_t *two, xpparam_t xpp; xdemitconf_t xecfg; - assert(!one || one->ptr[one->size] == '\0'); - assert(!two || two->ptr[two->size] == '\0'); if (!one) - return !regexec(regexp, two->ptr, 1, ®match, 0); + return !regexec_buf(regexp, two->ptr, two->size, + 1, ®match, 0); if (!two) - return !regexec(regexp, one->ptr, 1, ®match, 0); + return !regexec_buf(regexp, one->ptr, one->size, + 1, ®match, 0); /* * We have both sides; need to run textual diff and see if @@ -85,8 +81,8 @@ static unsigned int contains(mmfile_t *mf, regex_t *regexp, kwset_t kws) regmatch_t regmatch; int flags = 0; - assert(data[sz] == '\0'); - while (*data && !regexec(regexp, data, 1, ®match, flags)) { + while (*data && + !regexec_buf(regexp, data, sz, 1, ®match, flags)) { flags |= REG_NOTBOL; data += regmatch.rm_eo; if (*data && regmatch.rm_so == regmatch.rm_eo) diff --git a/git-compat-util.h b/git-compat-util.h index db89ba7..19128b3 100644 --- a/git-compat-util.h +++ b/git-compat-util.h @@ -965,6 +965,27 @@ void git_qsort(void *base, size_t nmemb, size_t size, #define qsort git_qsort #endif +static inline int regexec_buf(const regex_t *preg, const char *buf, size_t size, + size_t nmatch, regmatch_t pmatch[], int eflags) +{ +#ifdef REG_STARTEND + assert(nmatch > 0 && pmatch); + pmatch[0].rm_so = 0; + pmatch[0].rm_eo = size; + return regexec(preg, buf, nmatch, pmatch, eflags | REG_STARTEND); +#else + char *buf2 = xmalloc(size + 1); + int ret; + + memcpy(buf2, buf, size); + buf2[size] = '\0'; + ret = regexec(preg, buf2, nmatch, pmatch, eflags); + free(buf2); + + return ret; +#endif +} + #ifndef DIR_HAS_BSD_GROUP_SEMANTICS # define FORCE_DIR_SET_GID S_ISGID #else diff --git a/t/t4059-diff-pickaxe.sh b/t/t4061-diff-pickaxe.sh similarity index 91% rename from t/t4059-diff-pickaxe.sh rename to t/t4061-diff-pickaxe.sh index f0bf50b..5929f2e 100755 --- a/t/t4059-diff-pickaxe.sh +++ b/t/t4061-diff-pickaxe.sh @@ -14,7 +14,7 @@ test_expect_success setup ' test_tick && git commit -m "A 4k file" ' -test_expect_success '-G matches' ' +test_expect_failure '-G matches' ' git diff --name-only -G "^0{4096}$" HEAD^ >out && test 4096-zeroes.txt = "$(cat out)" ' diff --git a/xdiff-interface.c b/xdiff-interface.c index f34ea76..50702a2 100644 --- a/xdiff-interface.c +++ b/xdiff-interface.c @@ -214,11 +214,10 @@ struct ff_regs { static long ff_regexp(const char *line, long len, char *buffer, long buffer_size, void *priv) { - char *line_buffer; struct ff_regs *regs = priv; regmatch_t pmatch[2]; int i; - int result = -1; + int result; /* Exclude terminating newline (and cr) from matching */ if (len > 0 && line[len-1] == '\n') { @@ -228,18 +227,16 @@ static long ff_regexp(const char *line, long len, len--; } - line_buffer = xstrndup(line, len); /* make NUL terminated */ - for (i = 0; i < regs->nr; i++) { struct ff_reg *reg = regs->array + i; - if (!regexec(®->re, line_buffer, 2, pmatch, 0)) { + if (!regexec_buf(®->re, line, len, 2, pmatch, 0)) { if (reg->negate) - goto fail; + return -1; break; } } if (regs->nr <= i) - goto fail; + return -1; i = pmatch[1].rm_so >= 0 ? 1 : 0; line += pmatch[i].rm_so; result = pmatch[i].rm_eo - pmatch[i].rm_so; @@ -248,8 +245,6 @@ static long ff_regexp(const char *line, long len, while (result > 0 && (isspace(line[result - 1]))) result--; memcpy(buffer, line, result); - fail: - free(line_buffer); return result; } -- 2.10.0.windows.1.10.g803177d base-commit: 6ebdac1bab966b720d776aa43ca188fe378b1f4b
