X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=src%2Fjournal%2Fcoredump.c;h=7dea66e6fdd74bd4e396943cbb266a4efe587c1b;hp=bbec550784f8a79855c3808140af67c4092ae0ab;hb=b070e7f3c9ed680c821bd89d42506695f2438506;hpb=de0229ca36034981f6c380de39bf7ffd3c6b57fa

diff --git a/src/journal/coredump.c b/src/journal/coredump.c
index bbec55078..7dea66e6f 100644
--- a/src/journal/coredump.c
+++ b/src/journal/coredump.c
@@ -21,12 +21,15 @@
 
 #include <errno.h>
 #include <unistd.h>
+#include <stdio.h>
+#include <sys/prctl.h>
 
 #include <systemd/sd-journal.h>
 #include <systemd/sd-login.h>
 
 #include "log.h"
 #include "util.h"
+#include "special.h"
 
 #define COREDUMP_MAX (24*1024*1024)
 
@@ -40,21 +43,74 @@ enum {
         _ARG_MAX
 };
 
+static int divert_coredump(void) {
+        FILE *f;
+        int r;
+
+        log_info("Detected coredump of the journal daemon itself, diverting coredump to /var/lib/systemd/coredump/.");
+
+        mkdir_p("/var/lib/systemd/coredump", 0755);
+
+        f = fopen("/var/lib/systemd/coredump/core.systemd-journald", "we");
+        if (!f) {
+                log_error("Failed to create coredump file: %m");
+                return -errno;
+        }
+
+        for (;;) {
+                uint8_t buffer[4096];
+                size_t l, q;
+
+                l = fread(buffer, 1, sizeof(buffer), stdin);
+                if (l <= 0) {
+                        if (ferror(f)) {
+                                log_error("Failed to read coredump: %m");
+                                r = -errno;
+                                goto finish;
+                        }
+
+                        r = 0;
+                        break;
+                }
+
+                q = fwrite(buffer, 1, l, f);
+                if (q != l) {
+                        log_error("Failed to write coredump: %m");
+                        r = -errno;
+                        goto finish;
+                }
+        }
+
+        fflush(f);
+
+        if (ferror(f)) {
+                log_error("Failed to write coredump: %m");
+                r = -errno;
+        }
+
+finish:
+        fclose(f);
+        return r;
+}
+
 int main(int argc, char* argv[]) {
         int r, j = 0;
         char *p = NULL;
         ssize_t n;
         pid_t pid;
+        uid_t uid;
+        gid_t gid;
         struct iovec iovec[14];
         char *core_pid = NULL, *core_uid = NULL, *core_gid = NULL, *core_signal = NULL,
                 *core_timestamp = NULL, *core_comm = NULL, *core_exe = NULL, *core_unit = NULL,
                 *core_session = NULL, *core_message = NULL, *core_cmdline = NULL, *t;
 
-        log_set_target(LOG_TARGET_JOURNAL_OR_KMSG);
-        log_parse_environment();
-        log_open();
+        prctl(PR_SET_DUMPABLE, 0);
 
         if (argc != _ARG_MAX) {
+                log_set_target(LOG_TARGET_JOURNAL_OR_KMSG);
+                log_open();
+
                 log_error("Invalid number of arguments passed from kernel.");
                 r = -EINVAL;
                 goto finish;
@@ -62,31 +118,48 @@ int main(int argc, char* argv[]) {
 
         r = parse_pid(argv[ARG_PID], &pid);
         if (r < 0) {
+                log_set_target(LOG_TARGET_JOURNAL_OR_KMSG);
+                log_open();
+
                 log_error("Failed to parse PID.");
-                r = -EINVAL;
                 goto finish;
         }
 
-        p = malloc(9 + COREDUMP_MAX);
-        if (!p) {
-                log_error("Out of memory");
-                r = -ENOMEM;
-                goto finish;
+        if (sd_pid_get_unit(pid, &t) >= 0) {
+
+                if (streq(t, SPECIAL_JOURNALD_SERVICE)) {
+                        /* Make sure we don't make use of the journal,
+                         * if it's the journal which is crashing */
+                        log_set_target(LOG_TARGET_KMSG);
+                        log_open();
+
+                        r = divert_coredump();
+                        goto finish;
+                }
+
+                core_unit = strappend("COREDUMP_UNIT=", t);
+                free(t);
+
+                if (core_unit)
+                        IOVEC_SET_STRING(iovec[j++], core_unit);
         }
 
-        memcpy(p, "COREDUMP=", 9);
+        /* OK, now we know it's not the journal, hence make use of
+         * it */
+        log_set_target(LOG_TARGET_JOURNAL_OR_KMSG);
+        log_open();
 
-        n = loop_read(STDIN_FILENO, p + 9, COREDUMP_MAX, false);
-        if (n < 0) {
-                log_error("Failed to read core dump data: %s", strerror(-n));
-                r = (int) n;
+        r = parse_uid(argv[ARG_UID], &uid);
+        if (r < 0) {
+                log_error("Failed to parse UID.");
                 goto finish;
         }
 
-        zero(iovec);
-        iovec[j].iov_base = p;
-        iovec[j].iov_len = 9 + n;
-        j++;
+        r = parse_gid(argv[ARG_GID], &gid);
+        if (r < 0) {
+                log_error("Failed to parse GID.");
+                goto finish;
+        }
 
         core_pid = strappend("COREDUMP_PID=", argv[ARG_PID]);
         if (core_pid)
@@ -116,14 +189,6 @@ int main(int argc, char* argv[]) {
                         IOVEC_SET_STRING(iovec[j++], core_session);
         }
 
-        if (sd_pid_get_unit(pid, &t) >= 0) {
-                core_unit = strappend("COREDUMP_UNIT=", t);
-                free(t);
-
-                if (core_unit)
-                        IOVEC_SET_STRING(iovec[j++], core_unit);
-        }
-
         if (get_process_exe(pid, &t) >= 0) {
                 core_exe = strappend("COREDUMP_EXE=", t);
                 free(t);
@@ -151,6 +216,39 @@ int main(int argc, char* argv[]) {
         if (core_message)
                 IOVEC_SET_STRING(iovec[j++], core_message);
 
+        /* Now, let's drop privileges to become the user who owns the
+         * segfaulted process and allocate the coredump memory under
+         * his uid. This also ensures that the credentials journald
+         * will see are the ones of the coredumping user, thus making
+         * sure the user himself gets access to the core dump. */
+
+        if (setresgid(gid, gid, gid) < 0 ||
+            setresuid(uid, uid, uid) < 0) {
+                log_error("Failed to drop privileges: %m");
+                r = -errno;
+                goto finish;
+        }
+
+        p = malloc(9 + COREDUMP_MAX);
+        if (!p) {
+                log_error("Out of memory");
+                r = -ENOMEM;
+                goto finish;
+        }
+
+        memcpy(p, "COREDUMP=", 9);
+
+        n = loop_read(STDIN_FILENO, p + 9, COREDUMP_MAX, false);
+        if (n < 0) {
+                log_error("Failed to read core dump data: %s", strerror(-n));
+                r = (int) n;
+                goto finish;
+        }
+
+        iovec[j].iov_base = p;
+        iovec[j].iov_len = 9 + n;
+        j++;
+
         r = sd_journal_sendv(iovec, j);
         if (r < 0)
                 log_error("Failed to send coredump: %s", strerror(-r));