From b6c10945e68949edc6418f48ca7b1b748fefabe1 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= 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 #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");