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[stat-cache] fix handling of collisions, might have returned wrong data (fixes #2669)

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- don't remember splay_tree nodes for long (dir_node, file_node) after
  cache lookup; only remember the data they pointed to (sce for file
  entries, fam_node for dir entries)
- unset sce / fam_node when a collision (not matching path) is detected
- check again for collision before splaytree_insert; the entry in
  question is already at the top because it was splayed before. simply
  replace the data on collisions (and release the old data).
- check fam_node for collisions too
- splaytree_size handles NULL nodes too
- enable some force_assert lines (were in #ifdef DEBUG_STAT_CACHE before)

Differential Revision: https://review.lighttpd.net/D1

From: Stefan Bühler <stbuehler@web.de>

git-svn-id: svn://svn.lighttpd.net/lighttpd/branches/lighttpd-1.4.x@3039 152afb58-edef-0310-8abb-c4023f1b3aa9
svn/tags/lighttpd-1.4.38
Stefan Bühler 7 years ago
parent 90a9322121
commit 69f890e2c5
2 changed files with 50 additions and 54 deletions
Show Stats Download Patch File Download Diff File

1
NEWS
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@ -4,6 +4,7 @@ NEWS
====
- 1.4.38
* [stat-cache] fix handling of collisions, might have returned wrong data (fixes #2669)
- 1.4.37 - 2015-08-30
* [mod_proxy] remove debug log line from error log (fixes #2659)

103
src/stat_cache.c
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@ -369,7 +369,6 @@ handler_t stat_cache_get_entry(server *srv, connection *con, buffer *name, stat_
#ifdef HAVE_FAM_H
fam_dir_entry *fam_dir = NULL;
int dir_ndx = -1;
splay_tree *dir_node = NULL;
#endif
stat_cache_entry *sce = NULL;
stat_cache *sc;
@ -382,7 +381,6 @@ handler_t stat_cache_get_entry(server *srv, connection *con, buffer *name, stat_
#endif
int file_ndx;
splay_tree *file_node = NULL;
*ret_sce = NULL;
@ -413,9 +411,7 @@ handler_t stat_cache_get_entry(server *srv, connection *con, buffer *name, stat_
/* we have seen this file already and
* don't stat() it again in the same second */
file_node = sc->files;
sce = file_node->data;
sce = sc->files->data;
/* check if the name is the same, we might have a collision */
@ -427,17 +423,8 @@ handler_t stat_cache_get_entry(server *srv, connection *con, buffer *name, stat_
}
}
} else {
/* oops, a collision,
*
* file_node is used by the FAM check below to see if we know this file
* and if we can save a stat().
*
* BUT, the sce is not reset here as the entry into the cache is ok, we
* it is just not pointing to our requested file.
*
* */
file_node = NULL;
/* collision, forget about the entry */
sce = NULL;
}
} else {
#ifdef DEBUG_STAT_CACHE
@ -465,21 +452,21 @@ handler_t stat_cache_get_entry(server *srv, connection *con, buffer *name, stat_
sc->dirs = splaytree_splay(sc->dirs, dir_ndx);
if (sc->dirs && (sc->dirs->key == dir_ndx)) {
dir_node = sc->dirs;
}
if (dir_node && file_node) {
/* we found a file */
if ((NULL != sc->dirs) && (sc->dirs->key == dir_ndx)) {
fam_dir = sc->dirs->data;
sce = file_node->data;
fam_dir = dir_node->data;
/* check whether we got a collision */
if (buffer_is_equal(sc->dir_name, fam_dir->name)) {
/* test whether a found file cache entry is still ok */
if ((NULL != sce) && (fam_dir->version == sce->dir_version)) {
/* the stat()-cache entry is still ok */
if (fam_dir->version == sce->dir_version) {
/* the stat()-cache entry is still ok */
*ret_sce = sce;
return HANDLER_GO_ON;
*ret_sce = sce;
return HANDLER_GO_ON;
}
} else {
/* hash collision, forget about the entry */
fam_dir = NULL;
}
}
}
@ -511,30 +498,36 @@ handler_t stat_cache_get_entry(server *srv, connection *con, buffer *name, stat_
}
if (NULL == sce) {
#ifdef DEBUG_STAT_CACHE
int osize = splaytree_size(sc->files);
#endif
sce = stat_cache_entry_init();
buffer_copy_buffer(sce->name, name);
sc->files = splaytree_insert(sc->files, file_ndx, sce);
#ifdef DEBUG_STAT_CACHE
if (ctrl.size == 0) {
ctrl.size = 16;
ctrl.used = 0;
ctrl.ptr = malloc(ctrl.size * sizeof(*ctrl.ptr));
} else if (ctrl.size == ctrl.used) {
ctrl.size += 16;
ctrl.ptr = realloc(ctrl.ptr, ctrl.size * sizeof(*ctrl.ptr));
}
/* already splayed file_ndx */
if ((NULL != sc->files) && (sc->files->key == file_ndx)) {
/* hash collision: replace old entry */
stat_cache_entry_free(sc->files->data);
sc->files->data = sce;
} else {
int osize = splaytree_size(sc->files);
ctrl.ptr[ctrl.used++] = file_ndx;
sc->files = splaytree_insert(sc->files, file_ndx, sce);
force_assert(osize + 1 == splaytree_size(sc->files));
#ifdef DEBUG_STAT_CACHE
if (ctrl.size == 0) {
ctrl.size = 16;
ctrl.used = 0;
ctrl.ptr = malloc(ctrl.size * sizeof(*ctrl.ptr));
} else if (ctrl.size == ctrl.used) {
ctrl.size += 16;
ctrl.ptr = realloc(ctrl.ptr, ctrl.size * sizeof(*ctrl.ptr));
}
ctrl.ptr[ctrl.used++] = file_ndx;
#endif
}
force_assert(sc->files);
force_assert(sc->files->data == sce);
force_assert(osize + 1 == splaytree_size(sc->files));
#endif
}
sce->st = st;
@ -639,7 +632,7 @@ handler_t stat_cache_get_entry(server *srv, connection *con, buffer *name, stat_
#ifdef HAVE_FAM_H
if (srv->srvconf.stat_cache_engine == STAT_CACHE_ENGINE_FAM) {
/* is this directory already registered ? */
if (!dir_node) {
if (NULL == fam_dir) {
fam_dir = fam_dir_entry_init();
buffer_copy_buffer(fam_dir->name, sc->dir_name);
@ -660,19 +653,21 @@ handler_t stat_cache_get_entry(server *srv, connection *con, buffer *name, stat_
fam_dir_entry_free(&sc->fam, fam_dir);
fam_dir = NULL;
} else {
int osize = 0;
if (sc->dirs) {
osize = sc->dirs->size;
int osize = splaytree_size(sc->dirs);
/* already splayed dir_ndx */
if ((NULL != sc->dirs) && (sc->dirs->key == dir_ndx)) {
/* hash collision: replace old entry */
fam_dir_entry_free(&sc->fam, sc->dirs->data);
sc->dirs->data = fam_dir;
} else {
sc->dirs = splaytree_insert(sc->dirs, dir_ndx, fam_dir);
force_assert(osize == (splaytree_size(sc->dirs) - 1));
}
sc->dirs = splaytree_insert(sc->dirs, dir_ndx, fam_dir);
force_assert(sc->dirs);
force_assert(sc->dirs->data == fam_dir);
force_assert(osize == (sc->dirs->size - 1));
}
} else {
fam_dir = dir_node->data;
}
/* bind the fam_fc to the stat() cache entry */

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