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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.
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keszybz committed Dec 5, 2018
1 parent bc2762a commit 084eeb865ca63887098e0945fb4e93c852b91b0f
Showing with 38 additions and 30 deletions.
  1. +10 −0 src/basic/io-util.c
  2. +2 −0 src/basic/io-util.h
  3. +11 −20 src/coredump/coredump.c
  4. +15 −10 src/journal/journald-server.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;
}
@@ -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);
@@ -1063,19 +1063,10 @@ 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;
}
@@ -1125,36 +1116,36 @@ 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)
@@ -1222,7 +1213,7 @@ 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 */
}
@@ -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) */

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");
@@ -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");
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");

1 comment on commit 084eeb8

@nyetwurk

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nyetwurk commented on 084eeb8 Jan 20, 2019

This likely causes a regression
#11502

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