From b6c10945e68949edc6418f48ca7b1b748fefabe1 Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>

Date: Wed, 5 Dec 2018 18:38:39 +0100

Subject: [PATCH] journald: do not store the iovec entry for process

 commandline on stack

This fixes a crash where we would read the commandline, whose length is under

control of the sending program, and then crash when trying to create a stack

allocation for it.

CVE-2018-16864

https://bugzilla.redhat.com/show_bug.cgi?id=1653855

The message actually doesn't get written to disk, because

journal_file_append_entry() returns -E2BIG.

(cherry-picked from commit 084eeb865ca63887098e0945fb4e93c852b91b0f)

Resolves: #1664976

---

 src/basic/io-util.c           | 10 ++++++++++

 src/basic/io-util.h           |  2 ++

 src/coredump/coredump.c       | 31 +++++++++++--------------------

 src/journal/journald-server.c | 25 +++++++++++++++----------

 4 files changed, 38 insertions(+), 30 deletions(-)

diff --git a/src/basic/io-util.c b/src/basic/io-util.c

index 1f64cc933b..575398fbe6 100644

--- a/src/basic/io-util.c

+++ b/src/basic/io-util.c

@@ -8,6 +8,7 @@

 #include <unistd.h>

 #include "io-util.h"

+#include "string-util.h"

 #include "time-util.h"

 int flush_fd(int fd) {

@@ -252,3 +253,12 @@ ssize_t sparse_write(int fd, const void *p, size_t sz, size_t run_length) {

         return q - (const uint8_t*) p;

 }

+

+char* set_iovec_string_field(struct iovec *iovec, size_t *n_iovec, const char *field, const char *value) {

+        char *x;

+

+        x = strappend(field, value);

+        if (x)

+                iovec[(*n_iovec)++] = IOVEC_MAKE_STRING(x);

+        return x;

+}

diff --git a/src/basic/io-util.h b/src/basic/io-util.h

index ed189b5820..792a64ad5e 100644

--- a/src/basic/io-util.h

+++ b/src/basic/io-util.h

@@ -71,3 +71,5 @@ static inline bool FILE_SIZE_VALID_OR_INFINITY(uint64_t l) {

 #define IOVEC_MAKE(base, len) (struct iovec) IOVEC_INIT(base, len)

 #define IOVEC_INIT_STRING(string) IOVEC_INIT((char*) string, strlen(string))

 #define IOVEC_MAKE_STRING(string) (struct iovec) IOVEC_INIT_STRING(string)

+

+char* set_iovec_string_field(struct iovec *iovec, size_t *n_iovec, const char *field, const char *value);

diff --git a/src/coredump/coredump.c b/src/coredump/coredump.c

index d7dd81c1b4..ffa88f612d 100644

--- a/src/coredump/coredump.c

+++ b/src/coredump/coredump.c

@@ -1054,19 +1054,10 @@ static int send_iovec(const struct iovec iovec[], size_t n_iovec, int input_fd)

         return 0;

 }

-static char* set_iovec_field(struct iovec *iovec, size_t *n_iovec, const char *field, const char *value) {

-        char *x;

-

-        x = strappend(field, value);

-        if (x)

-                iovec[(*n_iovec)++] = IOVEC_MAKE_STRING(x);

-        return x;

-}

-

 static char* set_iovec_field_free(struct iovec *iovec, size_t *n_iovec, const char *field, char *value) {

         char *x;

-        x = set_iovec_field(iovec, n_iovec, field, value);

+        x = set_iovec_string_field(iovec, n_iovec, field, value);

         free(value);

         return x;

 }

@@ -1116,36 +1107,36 @@ static int gather_pid_metadata(

                         disable_coredumps();

                 }

-                set_iovec_field(iovec, n_iovec, "COREDUMP_UNIT=", context[CONTEXT_UNIT]);

+                set_iovec_string_field(iovec, n_iovec, "COREDUMP_UNIT=", context[CONTEXT_UNIT]);

         }

         if (cg_pid_get_user_unit(pid, &t) >= 0)

                 set_iovec_field_free(iovec, n_iovec, "COREDUMP_USER_UNIT=", t);

         /* The next few are mandatory */

-        if (!set_iovec_field(iovec, n_iovec, "COREDUMP_PID=", context[CONTEXT_PID]))

+        if (!set_iovec_string_field(iovec, n_iovec, "COREDUMP_PID=", context[CONTEXT_PID]))

                 return log_oom();

-        if (!set_iovec_field(iovec, n_iovec, "COREDUMP_UID=", context[CONTEXT_UID]))

+        if (!set_iovec_string_field(iovec, n_iovec, "COREDUMP_UID=", context[CONTEXT_UID]))

                 return log_oom();

-        if (!set_iovec_field(iovec, n_iovec, "COREDUMP_GID=", context[CONTEXT_GID]))

+        if (!set_iovec_string_field(iovec, n_iovec, "COREDUMP_GID=", context[CONTEXT_GID]))

                 return log_oom();

-        if (!set_iovec_field(iovec, n_iovec, "COREDUMP_SIGNAL=", context[CONTEXT_SIGNAL]))

+        if (!set_iovec_string_field(iovec, n_iovec, "COREDUMP_SIGNAL=", context[CONTEXT_SIGNAL]))

                 return log_oom();

-        if (!set_iovec_field(iovec, n_iovec, "COREDUMP_RLIMIT=", context[CONTEXT_RLIMIT]))

+        if (!set_iovec_string_field(iovec, n_iovec, "COREDUMP_RLIMIT=", context[CONTEXT_RLIMIT]))

                 return log_oom();

-        if (!set_iovec_field(iovec, n_iovec, "COREDUMP_HOSTNAME=", context[CONTEXT_HOSTNAME]))

+        if (!set_iovec_string_field(iovec, n_iovec, "COREDUMP_HOSTNAME=", context[CONTEXT_HOSTNAME]))

                 return log_oom();

-        if (!set_iovec_field(iovec, n_iovec, "COREDUMP_COMM=", context[CONTEXT_COMM]))

+        if (!set_iovec_string_field(iovec, n_iovec, "COREDUMP_COMM=", context[CONTEXT_COMM]))

                 return log_oom();

         if (context[CONTEXT_EXE] &&

-            !set_iovec_field(iovec, n_iovec, "COREDUMP_EXE=", context[CONTEXT_EXE]))

+            !set_iovec_string_field(iovec, n_iovec, "COREDUMP_EXE=", context[CONTEXT_EXE]))

                 return log_oom();

         if (sd_pid_get_session(pid, &t) >= 0)

@@ -1213,7 +1204,7 @@ static int gather_pid_metadata(

                 iovec[(*n_iovec)++] = IOVEC_MAKE_STRING(t);

         if (safe_atoi(context[CONTEXT_SIGNAL], &signo) >= 0 && SIGNAL_VALID(signo))

-                set_iovec_field(iovec, n_iovec, "COREDUMP_SIGNAL_NAME=SIG", signal_to_string(signo));

+                set_iovec_string_field(iovec, n_iovec, "COREDUMP_SIGNAL_NAME=SIG", signal_to_string(signo));

         return 0; /* we successfully acquired all metadata */

 }

diff --git a/src/journal/journald-server.c b/src/journal/journald-server.c

index ce2446a2f1..8de45552f6 100644

--- a/src/journal/journald-server.c

+++ b/src/journal/journald-server.c

@@ -753,6 +753,7 @@ static void dispatch_message_real(

                 pid_t object_pid) {

         char source_time[sizeof("_SOURCE_REALTIME_TIMESTAMP=") + DECIMAL_STR_MAX(usec_t)];

+        _cleanup_free_ char *cmdline1 = NULL, *cmdline2 = NULL;

         uid_t journal_uid;

         ClientContext *o;

@@ -769,20 +770,23 @@ static void dispatch_message_real(

                 IOVEC_ADD_NUMERIC_FIELD(iovec, n, c->uid, uid_t, uid_is_valid, UID_FMT, "_UID");

                 IOVEC_ADD_NUMERIC_FIELD(iovec, n, c->gid, gid_t, gid_is_valid, GID_FMT, "_GID");

-                IOVEC_ADD_STRING_FIELD(iovec, n, c->comm, "_COMM");

-                IOVEC_ADD_STRING_FIELD(iovec, n, c->exe, "_EXE");

-                IOVEC_ADD_STRING_FIELD(iovec, n, c->cmdline, "_CMDLINE");

-                IOVEC_ADD_STRING_FIELD(iovec, n, c->capeff, "_CAP_EFFECTIVE");

+                IOVEC_ADD_STRING_FIELD(iovec, n, c->comm, "_COMM"); /* At most TASK_COMM_LENGTH (16 bytes) */

+                IOVEC_ADD_STRING_FIELD(iovec, n, c->exe, "_EXE"); /* A path, so at most PATH_MAX (4096 bytes) */

-                IOVEC_ADD_SIZED_FIELD(iovec, n, c->label, c->label_size, "_SELINUX_CONTEXT");

+                if (c->cmdline)

+                        /* At most _SC_ARG_MAX (2MB usually), which is too much to put on stack.

+                         * Let's use a heap allocation for this one. */

+                        cmdline1 = set_iovec_string_field(iovec, &n, "_CMDLINE=", c->cmdline);

+                IOVEC_ADD_STRING_FIELD(iovec, n, c->capeff, "_CAP_EFFECTIVE"); /* Read from /proc/.../status */

+                IOVEC_ADD_SIZED_FIELD(iovec, n, c->label, c->label_size, "_SELINUX_CONTEXT");

                 IOVEC_ADD_NUMERIC_FIELD(iovec, n, c->auditid, uint32_t, audit_session_is_valid, "%" PRIu32, "_AUDIT_SESSION");

                 IOVEC_ADD_NUMERIC_FIELD(iovec, n, c->loginuid, uid_t, uid_is_valid, UID_FMT, "_AUDIT_LOGINUID");

-                IOVEC_ADD_STRING_FIELD(iovec, n, c->cgroup, "_SYSTEMD_CGROUP");

+                IOVEC_ADD_STRING_FIELD(iovec, n, c->cgroup, "_SYSTEMD_CGROUP"); /* A path */

                 IOVEC_ADD_STRING_FIELD(iovec, n, c->session, "_SYSTEMD_SESSION");

                 IOVEC_ADD_NUMERIC_FIELD(iovec, n, c->owner_uid, uid_t, uid_is_valid, UID_FMT, "_SYSTEMD_OWNER_UID");

-                IOVEC_ADD_STRING_FIELD(iovec, n, c->unit, "_SYSTEMD_UNIT");

+                IOVEC_ADD_STRING_FIELD(iovec, n, c->unit, "_SYSTEMD_UNIT"); /* Unit names are bounded by UNIT_NAME_MAX */

                 IOVEC_ADD_STRING_FIELD(iovec, n, c->user_unit, "_SYSTEMD_USER_UNIT");

                 IOVEC_ADD_STRING_FIELD(iovec, n, c->slice, "_SYSTEMD_SLICE");

                 IOVEC_ADD_STRING_FIELD(iovec, n, c->user_slice, "_SYSTEMD_USER_SLICE");

@@ -803,13 +807,14 @@ static void dispatch_message_real(

                 IOVEC_ADD_NUMERIC_FIELD(iovec, n, o->uid, uid_t, uid_is_valid, UID_FMT, "OBJECT_UID");

                 IOVEC_ADD_NUMERIC_FIELD(iovec, n, o->gid, gid_t, gid_is_valid, GID_FMT, "OBJECT_GID");

+                /* See above for size limits, only ->cmdline may be large, so use a heap allocation for it. */

                 IOVEC_ADD_STRING_FIELD(iovec, n, o->comm, "OBJECT_COMM");

                 IOVEC_ADD_STRING_FIELD(iovec, n, o->exe, "OBJECT_EXE");

-                IOVEC_ADD_STRING_FIELD(iovec, n, o->cmdline, "OBJECT_CMDLINE");

-                IOVEC_ADD_STRING_FIELD(iovec, n, o->capeff, "OBJECT_CAP_EFFECTIVE");

+                if (o->cmdline)

+                        cmdline2 = set_iovec_string_field(iovec, &n, "OBJECT_CMDLINE=", o->cmdline);

+                IOVEC_ADD_STRING_FIELD(iovec, n, o->capeff, "OBJECT_CAP_EFFECTIVE");

                 IOVEC_ADD_SIZED_FIELD(iovec, n, o->label, o->label_size, "OBJECT_SELINUX_CONTEXT");

-

                 IOVEC_ADD_NUMERIC_FIELD(iovec, n, o->auditid, uint32_t, audit_session_is_valid, "%" PRIu32, "OBJECT_AUDIT_SESSION");

                 IOVEC_ADD_NUMERIC_FIELD(iovec, n, o->loginuid, uid_t, uid_is_valid, UID_FMT, "OBJECT_AUDIT_LOGINUID");