Stop reusing cache_entry in dir_entry; doing so causes a
use-after-free bug.
During merges, we free entries that we no longer need in the
destination index. But those entries might have also been stored in
the dir_entry cache, and when a later call to add_to_index found them,
they would be used after being freed.
To prevent this, change dir_entry to store a copy of the name instead
of a pointer to a cache_entry. This entails some refactoring of code
that expects the cache_entry.
Keith McGuigan <kmcguigan@xxxxxxxxxxx> diagnosed this bug and wrote
the initial patch, but this version does not use any of Keith's code.
Helped-by: Keith McGuigan <kmcguigan@xxxxxxxxxxx>
Helped-by: Junio C Hamano <gitster@xxxxxxxxx>
Signed-off-by: David Turner <dturner@xxxxxxxxxxxxxxxx>
---
cache.h | 3 ++-
dir.c | 22 ++++------------------
name-hash.c | 54 ++++++++++++++++++++++++++++--------------------------
read-cache.c | 16 +---------------
4 files changed, 35 insertions(+), 60 deletions(-)
diff --git a/cache.h b/cache.h
index 752031e..ccc329a 100644
--- a/cache.h
+++ b/cache.h
@@ -520,7 +520,8 @@ extern int write_locked_index(struct index_state *, struct lock_file *lock, unsi
extern int discard_index(struct index_state *);
extern int unmerged_index(const struct index_state *);
extern int verify_path(const char *path);
-extern struct cache_entry *index_dir_exists(struct index_state *istate, const char *name, int namelen);
+extern int index_dir_exists(struct index_state *istate, const char *name, int namelen);
+extern void adjust_dirname_case(struct index_state *istate, char *name);
extern struct cache_entry *index_file_exists(struct index_state *istate, const char *name, int namelen, int igncase);
extern int index_name_pos(const struct index_state *, const char *name, int namelen);
#define ADD_CACHE_OK_TO_ADD 1 /* Ok to add */
diff --git a/dir.c b/dir.c
index b90484a..c982aac 100644
--- a/dir.c
+++ b/dir.c
@@ -1279,29 +1279,15 @@ enum exist_status {
*/
static enum exist_status directory_exists_in_index_icase(const char *dirname, int len)
{
- const struct cache_entry *ce = cache_dir_exists(dirname, len);
- unsigned char endchar;
+ struct cache_entry *ce;
- if (!ce)
- return index_nonexistent;
- endchar = ce->name[len];
-
- /*
- * The cache_entry structure returned will contain this dirname
- * and possibly additional path components.
- */
- if (endchar == '/')
+ if (cache_dir_exists(dirname, len))
return index_directory;
- /*
- * If there are no additional path components, then this cache_entry
- * represents a submodule. Submodules, despite being directories,
- * are stored in the cache without a closing slash.
- */
- if (!endchar && S_ISGITLINK(ce->ce_mode))
+ ce = cache_file_exists(dirname, len, ignore_case);
+ if (ce && S_ISGITLINK(ce->ce_mode))
return index_gitdir;
- /* This should never be hit, but it exists just in case. */
return index_nonexistent;
}
diff --git a/name-hash.c b/name-hash.c
index 702cd05..332ba95 100644
--- a/name-hash.c
+++ b/name-hash.c
@@ -11,16 +11,16 @@
struct dir_entry {
struct hashmap_entry ent;
struct dir_entry *parent;
- struct cache_entry *ce;
int nr;
unsigned int namelen;
+ char name[FLEX_ARRAY];
};
static int dir_entry_cmp(const struct dir_entry *e1,
const struct dir_entry *e2, const char *name)
{
- return e1->namelen != e2->namelen || strncasecmp(e1->ce->name,
- name ? name : e2->ce->name, e1->namelen);
+ return e1->namelen != e2->namelen || strncasecmp(e1->name,
+ name ? name : e2->name, e1->namelen);
}
static struct dir_entry *find_dir_entry(struct index_state *istate,
@@ -41,14 +41,6 @@ static struct dir_entry *hash_dir_entry(struct index_state *istate,
* closing slash. Despite submodules being a directory, they never
* reach this point, because they are stored
* in index_state.name_hash (as ordinary cache_entries).
- *
- * Note that the cache_entry stored with the dir_entry merely
- * supplies the name of the directory (up to dir_entry.namelen). We
- * track the number of 'active' files in a directory in dir_entry.nr,
- * so we can tell if the directory is still relevant, e.g. for git
- * status. However, if cache_entries are removed, we cannot pinpoint
- * an exact cache_entry that's still active. It is very possible that
- * multiple dir_entries point to the same cache_entry.
*/
struct dir_entry *dir;
@@ -63,10 +55,10 @@ static struct dir_entry *hash_dir_entry(struct index_state *istate,
dir = find_dir_entry(istate, ce->name, namelen);
if (!dir) {
/* not found, create it and add to hash table */
- dir = xcalloc(1, sizeof(struct dir_entry));
+ dir = xcalloc(1, sizeof(struct dir_entry) + namelen + 1);
hashmap_entry_init(dir, memihash(ce->name, namelen));
dir->namelen = namelen;
- dir->ce = ce;
+ strncpy(dir->name, ce->name, namelen);
hashmap_add(&istate->dir_hash, dir);
/* recursively add missing parent directories */
@@ -188,26 +180,36 @@ static int same_name(const struct cache_entry *ce, const char *name, int namelen
return slow_same_name(name, namelen, ce->name, len);
}
-struct cache_entry *index_dir_exists(struct index_state *istate, const char *name, int namelen)
+int index_dir_exists(struct index_state *istate, const char *name, int namelen)
{
- struct cache_entry *ce;
struct dir_entry *dir;
lazy_init_name_hash(istate);
dir = find_dir_entry(istate, name, namelen);
- if (dir && dir->nr)
- return dir->ce;
+ return dir && dir->nr;
+}
- /*
- * It might be a submodule. Unlike plain directories, which are stored
- * in the dir-hash, submodules are stored in the name-hash, so check
- * there, as well.
- */
- ce = index_file_exists(istate, name, namelen, 1);
- if (ce && S_ISGITLINK(ce->ce_mode))
- return ce;
+void adjust_dirname_case(struct index_state *istate, char *name)
+{
+ const char *startPtr = name;
+ const char *ptr = startPtr;
- return NULL;
+ lazy_init_name_hash(istate);
+ while (*ptr) {
+ while (*ptr && *ptr != '/')
+ ptr++;
+
+ if (*ptr == '/') {
+ struct dir_entry *dir;
+
+ ptr++;
+ dir = find_dir_entry(istate, name, ptr - name + 1);
+ if (dir) {
+ memcpy((void *)startPtr, dir->name + (startPtr - name), ptr - startPtr);
+ startPtr = ptr;
+ }
+ }
+ }
}
struct cache_entry *index_file_exists(struct index_state *istate, const char *name, int namelen, int icase)
diff --git a/read-cache.c b/read-cache.c
index 87204a5..de22df2 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -679,21 +679,7 @@ int add_to_index(struct index_state *istate, const char *path, struct stat *st,
* entry's directory case.
*/
if (ignore_case) {
- const char *startPtr = ce->name;
- const char *ptr = startPtr;
- while (*ptr) {
- while (*ptr && *ptr != '/')
- ++ptr;
- if (*ptr == '/') {
- struct cache_entry *foundce;
- ++ptr;
- foundce = index_dir_exists(istate, ce->name, ptr - ce->name - 1);
- if (foundce) {
- memcpy((void *)startPtr, foundce->name + (startPtr - ce->name), ptr - startPtr);
- startPtr = ptr;
- }
- }
- }
+ adjust_dirname_case(istate, ce->name);
}
alias = index_file_exists(istate, ce->name, ce_namelen(ce), ignore_case);
--
2.4.2.644.g97b850b-twtrsrc
--
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