'git status' segfaults if a directory is longer than PATH_MAX, because
processing .gitignore files in prep_exclude() writes past the end of a
PATH_MAX-bounded buffer.

Remove the limitation by using strbuf instead.

Note: this fix just 'abuses' strbuf as string allocator, len is always 0.
prep_exclude() can probably be simplified using more strbuf APIs.

Signed-off-by: Karsten Blees <bl...@dcon.de>
---
 dir.c | 35 +++++++++++++++++++----------------
 dir.h |  4 ++--
 2 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/dir.c b/dir.c
index e65888d..8d4d83c 100644
--- a/dir.c
+++ b/dir.c
@@ -798,7 +798,7 @@ static void prep_exclude(struct dir_struct *dir, const char 
*base, int baselen)
         * path being checked. */
        while ((stk = dir->exclude_stack) != NULL) {
                if (stk->baselen <= baselen &&
-                   !strncmp(dir->basebuf, base, stk->baselen))
+                   !strncmp(dir->base.buf, base, stk->baselen))
                        break;
                el = &group->el[dir->exclude_stack->exclude_ix];
                dir->exclude_stack = stk->prev;
@@ -833,48 +833,50 @@ static void prep_exclude(struct dir_struct *dir, const 
char *base, int baselen)
                stk->baselen = cp - base;
                stk->exclude_ix = group->nr;
                el = add_exclude_list(dir, EXC_DIRS, NULL);
-               memcpy(dir->basebuf + current, base + current,
+               strbuf_grow(&dir->base, stk->baselen);
+               memcpy(dir->base.buf + current, base + current,
                       stk->baselen - current);
 
                /* Abort if the directory is excluded */
                if (stk->baselen) {
                        int dt = DT_DIR;
-                       dir->basebuf[stk->baselen - 1] = 0;
+                       dir->base.buf[stk->baselen - 1] = 0;
                        dir->exclude = last_exclude_matching_from_lists(dir,
-                               dir->basebuf, stk->baselen - 1,
-                               dir->basebuf + current, &dt);
-                       dir->basebuf[stk->baselen - 1] = '/';
+                               dir->base.buf, stk->baselen - 1,
+                               dir->base.buf + current, &dt);
+                       dir->base.buf[stk->baselen - 1] = '/';
                        if (dir->exclude &&
                            dir->exclude->flags & EXC_FLAG_NEGATIVE)
                                dir->exclude = NULL;
                        if (dir->exclude) {
-                               dir->basebuf[stk->baselen] = 0;
+                               dir->base.buf[stk->baselen] = 0;
                                dir->exclude_stack = stk;
                                return;
                        }
                }
 
-               /* Try to read per-directory file unless path is too long */
-               if (dir->exclude_per_dir &&
-                   stk->baselen + strlen(dir->exclude_per_dir) < PATH_MAX) {
-                       strcpy(dir->basebuf + stk->baselen,
+               /* Try to read per-directory file */
+               if (dir->exclude_per_dir) {
+                       strbuf_grow(&dir->base, stk->baselen +
+                                   strlen(dir->exclude_per_dir));
+                       strcpy(dir->base.buf + stk->baselen,
                                        dir->exclude_per_dir);
                        /*
-                        * dir->basebuf gets reused by the traversal, but we
+                        * dir->base gets reused by the traversal, but we
                         * need fname to remain unchanged to ensure the src
                         * member of each struct exclude correctly
                         * back-references its source file.  Other invocations
                         * of add_exclude_list provide stable strings, so we
                         * strdup() and free() here in the caller.
                         */
-                       el->src = strdup(dir->basebuf);
-                       add_excludes_from_file_to_list(dir->basebuf,
-                                       dir->basebuf, stk->baselen, el, 1);
+                       el->src = strdup(dir->base.buf);
+                       add_excludes_from_file_to_list(dir->base.buf,
+                                       dir->base.buf, stk->baselen, el, 1);
                }
                dir->exclude_stack = stk;
                current = stk->baselen;
        }
-       dir->basebuf[baselen] = '\0';
+       dir->base.buf[baselen] = '\0';
 }
 
 /*
@@ -1671,4 +1673,5 @@ void clear_directory(struct dir_struct *dir)
                free(stk);
                stk = prev;
        }
+       strbuf_release(&dir->base);
 }
diff --git a/dir.h b/dir.h
index 55e5345..e870fb6 100644
--- a/dir.h
+++ b/dir.h
@@ -111,13 +111,13 @@ struct dir_struct {
         * per-directory exclude lists.
         *
         * exclude_stack points to the top of the exclude_stack, and
-        * basebuf contains the full path to the current
+        * base contains the full path to the current
         * (sub)directory in the traversal. Exclude points to the
         * matching exclude struct if the directory is excluded.
         */
        struct exclude_stack *exclude_stack;
        struct exclude *exclude;
-       char basebuf[PATH_MAX];
+       struct strbuf base;
 };
 
 /*
-- 
1.9.4.msysgit.0.5.g1471ac1

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