journal: map objects to context set by caller, not by actual object type

[elogind.git] / src / journal / mmap-cache.c

diff --git a/src/journal/mmap-cache.c b/src/journal/mmap-cache.c
index 908562da27a45e922f5ddccfe31de12d0934a98b..c57c1623c5c01e870fed95fa9804e15ad676a524 100644 (file)
--- a/src/journal/mmap-cache.c
+++ b/src/journal/mmap-cache.c
@@ -83,7 +83,13 @@ struct MMapCache {
 };
 
 #define WINDOWS_MIN 64
-#define WINDOW_SIZE (8ULL*1024ULL*1024ULL)
+
+#ifdef ENABLE_DEBUG_MMAP_CACHE
+/* Tiny windows increase mmap activity and the chance of exposing unsafe use. */
+# define WINDOW_SIZE (page_size())
+#else
+# define WINDOW_SIZE (8ULL*1024ULL*1024ULL)
+#endif
 
 MMapCache* mmap_cache_new(void) {
         MMapCache *m;
@@ -187,11 +193,17 @@ static void context_detach_window(Context *c) {
 
         if (!w->contexts && w->keep_always == 0) {
                 /* Not used anymore? */
+#ifdef ENABLE_DEBUG_MMAP_CACHE
+                /* Unmap unused windows immediately to expose use-after-unmap
+                 * by SIGSEGV. */
+                window_free(w);
+#else
                 LIST_PREPEND(unused, c->cache->unused, w);
                 if (!c->cache->last_unused)
                         c->cache->last_unused = w;
 
                 w->in_unused = true;
+#endif
         }
 }
 
@@ -227,7 +239,7 @@ static Context *context_add(MMapCache *m, unsigned id) {
         if (c)
                 return c;
 
-        r = hashmap_ensure_allocated(&m->contexts, trivial_hash_func, trivial_compare_func);
+        r = hashmap_ensure_allocated(&m->contexts, NULL);
         if (r < 0)
                 return NULL;
 
@@ -281,7 +293,7 @@ static FileDescriptor* fd_add(MMapCache *m, int fd) {
         if (f)
                 return f;
 
-        r = hashmap_ensure_allocated(&m->fds, trivial_hash_func, trivial_compare_func);
+        r = hashmap_ensure_allocated(&m->fds, NULL);
         if (r < 0)
                 return NULL;
 
@@ -352,7 +364,8 @@ static int try_context(
                 bool keep_always,
                 uint64_t offset,
                 size_t size,
-                void **ret) {
+                void **ret,
+                void **release_cookie) {
 
         Context *c;
 
@@ -381,6 +394,8 @@ static int try_context(
 
         if (ret)
                 *ret = (uint8_t*) c->window->ptr + (offset - c->window->offset);
+        if (keep_always && release_cookie)
+                *release_cookie = c->window;
         return 1;
 }
 
@@ -392,7 +407,8 @@ static int find_mmap(
                 bool keep_always,
                 uint64_t offset,
                 size_t size,
-                void **ret) {
+                void **ret,
+                void **release_cookie) {
 
         FileDescriptor *f;
         Window *w;
@@ -425,6 +441,8 @@ static int find_mmap(
 
         if (ret)
                 *ret = (uint8_t*) w->ptr + (offset - w->offset);
+        if (keep_always && release_cookie)
+                *release_cookie = c->window;
         return 1;
 }
 
@@ -437,7 +455,8 @@ static int add_mmap(
                 uint64_t offset,
                 size_t size,
                 struct stat *st,
-                void **ret) {
+                void **ret,
+                void **release_cookie) {
 
         uint64_t woffset, wsize;
         Context *c;
@@ -521,6 +540,8 @@ static int add_mmap(
 
         if (ret)
                 *ret = (uint8_t*) w->ptr + (offset - w->offset);
+        if (keep_always && release_cookie)
+                *release_cookie = c->window;
         return 1;
 
 outofmem:
@@ -537,7 +558,8 @@ int mmap_cache_get(
                 uint64_t offset,
                 size_t size,
                 struct stat *st,
-                void **ret) {
+                void **ret,
+                void **release_cookie) {
 
         int r;
 
@@ -547,14 +569,14 @@ int mmap_cache_get(
         assert(size > 0);
 
         /* Check whether the current context is the right one already */
-        r = try_context(m, fd, prot, context, keep_always, offset, size, ret);
+        r = try_context(m, fd, prot, context, keep_always, offset, size, ret, release_cookie);
         if (r != 0) {
                 m->n_hit ++;
                 return r;
         }
 
         /* Search for a matching mmap */
-        r = find_mmap(m, fd, prot, context, keep_always, offset, size, ret);
+        r = find_mmap(m, fd, prot, context, keep_always, offset, size, ret, release_cookie);
         if (r != 0) {
                 m->n_hit ++;
                 return r;
@@ -563,16 +585,13 @@ int mmap_cache_get(
         m->n_missed++;
 
         /* Create a new mmap */
-        return add_mmap(m, fd, prot, context, keep_always, offset, size, st, ret);
+        return add_mmap(m, fd, prot, context, keep_always, offset, size, st, ret, release_cookie);
 }
 
 int mmap_cache_release(
                 MMapCache *m,
                 int fd,
-                int prot,
-                unsigned context,
-                uint64_t offset,
-                size_t size) {
+                void *release_cookie) {
 
         FileDescriptor *f;
         Window *w;
@@ -580,7 +599,6 @@ int mmap_cache_release(
         assert(m);
         assert(m->n_ref > 0);
         assert(fd >= 0);
-        assert(size > 0);
 
         f = hashmap_get(m->fds, INT_TO_PTR(fd + 1));
         if (!f)
@@ -589,7 +607,7 @@ int mmap_cache_release(
         assert(f->fd == fd);
 
         LIST_FOREACH(by_fd, w, f->windows)
-                if (window_matches(w, fd, prot, offset, size))
+                if (w == release_cookie)
                         break;
 
         if (!w)