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journald: do not store the iovec entry for process commandline on stack

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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.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek
2019-01-09 23:41:53 +01:00
parent bc2762a309
commit 084eeb865c
4 changed files with 38 additions and 30 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/journal/journald-server.c
+15 -10
View File
@@ -905,6 +905,7 @@ 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;
@@ -921,20 +922,23 @@ 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) */
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");
@@ -955,13 +959,14 @@ 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");
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");