From e1130b774bef1ae7668fcebff8361ef8ac7c6ce2 Mon Sep 17 00:00:00 2001
From: Colin Patrick McCabe <cmccabe@alumni.cmu.edu>
Date: Fri, 13 May 2011 15:12:16 -0700
Subject: [PATCH] Fix race in core file limiting
Fix time-of-use / time-of-check race in core file limiting logic.
Signed-off-by: Colin McCabe <colin.mccabe@dreamhost.com>
---
handle_core.c | 134 ++++++++++++++++++++++++++++++++++----------------------
1 files changed, 81 insertions(+), 53 deletions(-)
diff --git a/handle_core.c b/handle_core.c
index ce81772..203ecda 100644
--- a/handle_core.c
+++ b/handle_core.c
@@ -16,7 +16,9 @@
#include <unistd.h>
#define BUF_SIZE 1024
-#define CORE_PATTERN "core.*"
+#define CORE_PREFIX "core."
+#define CORE_PREFIX_SZ (sizeof(CORE_PREFIX)-1)
+#define MAX_CORE_SCAN 500000
/*
* Core file handler
@@ -27,49 +29,88 @@
* /proc/sys/kernel/core_pattern
*/
-/* Count the number of core files we have. */
-static int count_core_files(const char *core_dir)
+/* Compare two core file names. We want reverse alphabetical order */
+static int compare_core_file_names(const void *a, const void *b)
{
- struct dirent *de;
- int count = 0;
- DIR *dp = opendir(core_dir);
+ const char *ca = *((const char **)a);
+ const char *cb = *((const char **)b);
+ return strcmp(cb, ca);
+}
+
+/* Step through core_dir and delete core files which have old looking names */
+static int limit_core_files(const char *core_dir, int max_cores)
+{
+ int deleted = 0, i, ret, num_cores = 0, alloc_cores = 64;
+ DIR *dp;
+ char **cores = malloc(sizeof(char*) * alloc_cores);
+
+ if (cores == NULL) {
+ ret = -ENOMEM;
+ goto done;
+ }
+ dp = opendir(core_dir);
if (!dp) {
- int err = errno;
- return -err;
+ ret = -errno;
+ goto done;
}
-
+ /* Scan through core files. If the number of files we're looking at is
+ * getting too large, we content ourselves with just what we've already
+ * scanned. This does mean we could delete newer files than we really
+ * intend. However, we need to avoid allocating a ridiculous amount of
+ * memory.
+ */
while (1) {
- de = readdir(dp);
+ struct dirent *de = readdir(dp);
if (!de)
break;
- if (fnmatch(CORE_PATTERN, de->d_name, 0) == 0) {
- count++;
+ /* ignore non-core files */
+ if (strncmp(de->d_name, CORE_PREFIX, CORE_PREFIX_SZ))
+ continue;
+ cores[num_cores] = strdup(de->d_name);
+ if (!cores[num_cores])
+ break;
+ num_cores++;
+ if (num_cores > MAX_CORE_SCAN)
+ break;
+ if (num_cores == alloc_cores) {
+ char **newptr = realloc(cores, sizeof(char*) * alloc_cores * 2);
+ if (!newptr)
+ break;
+ cores = newptr;
+ alloc_cores *= 2;
}
}
- closedir(dp);
- return count;
-}
-
-/* Unlink the core which sorts the first in the glob sort order. */
-static int unlink_core(const char *core_dir)
-{
- int ret;
- char path[PATH_MAX];
- glob_t g;
-
- snprintf(path, PATH_MAX, "%s/%s", core_dir, CORE_PATTERN);
- ret = glob(path, GLOB_ERR, NULL, &g);
- if (ret != 0) {
- return EIO;
+ qsort(cores, num_cores, sizeof(char**), compare_core_file_names);
+ /* delete core files which are too old. */
+ for (i = num_cores - 1; i >= max_cores; i--) {
+ char path[PATH_MAX];
+ snprintf(path, sizeof(path), "%s/%s", core_dir, cores[i]);
+ if (unlink(path) == 0) {
+ deleted++;
+ continue;
+ }
+ /* ignore ENOENT here. We may be racing with another
+ * handle_core process which deleted the old core first. */
+ ret = -errno;
+ if (ret != -ENOENT) {
+ syslog(LOG_USER | LOG_ERR, "unlink(%s) "
+ "error: %d (%s)",
+ cores[i], ret, strerror(ret));
+ goto done;
+ }
}
- if (g.gl_pathc == 0)
- return ENOENT;
- if (unlink(g.gl_pathv[0])) {
- globfree(&g);
- return errno;
+ ret = deleted;
+done:
+ if (cores) {
+ for (i = 0; i < num_cores; ++i) {
+ if (cores[i])
+ free(cores[i]);
+ }
+ free(cores);
}
- globfree(&g);
- return 0;
+ if (dp)
+ closedir(dp);
+ return ret;
}
/* Print the new core name into a buffer of size PATH_MAX */
@@ -190,12 +231,10 @@ core file name: %s/%s\r\n\
int main(int argc, char **argv)
{
- int ret, done = 0;
+ int max_cores, deleted, ret, done = 0;
char *exe_name, *core_dir, *email;
char core_name[PATH_MAX];
FILE *fp;
- int num_coref, num_deleted;
- int max_cores;
/* Write the core to a file */
ret = parse_options(argc, argv, &max_cores, &exe_name, &core_dir,
@@ -240,21 +279,10 @@ int main(int argc, char **argv)
fclose(fp);
/* Make sure we don't have too many cores sitting around. */
- num_coref = count_core_files(core_dir);
- num_deleted = 0;
- if (num_coref < 0) {
- syslog(LOG_USER | LOG_ERR, "count_core_files failed with error "
- "code %d\n", num_coref);
- return num_coref;
- }
- while (num_coref > max_cores) {
- int ret = unlink_core(core_dir);
- if (ret) {
- syslog(LOG_USER | LOG_ERR, "unlink_core failed with error "
- "code %d\n", ret);
- }
- num_coref--;
- num_deleted++;
+ deleted = limit_core_files(core_dir, max_cores);
+ if (deleted < 0) {
+ syslog(LOG_USER | LOG_ERR, "error limiting number of core "
+ "files: %d", deleted);
}
ret = send_mail(exe_name, core_dir, core_name, email);
@@ -264,6 +292,6 @@ int main(int argc, char **argv)
}
syslog(LOG_USER | LOG_ERR, "wrote core %s. Deleted %d extra core%s\n",
- core_name, num_deleted, ((num_deleted == 1) ? "" : "s"));
+ core_name, deleted, ((deleted == 1) ? "" : "s"));
return 0;
}
--
1.6.6.rc1.39.g9a42