From 6298317e2d0dffb1ff4ecebedb8709645de36b6a 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 18:48:23 +0100

Subject: [PATCH] basic/process-util: limit command line lengths to _SC_ARG_MAX

This affects systemd-journald and systemd-coredump.

Example entry:

$ journalctl -o export -n1 'MESSAGE=Something logged'

__CURSOR=s=976542d120c649f494471be317829ef9;i=34e;b=4871e4c474574ce4a462dfe3f1c37f06;m=c7d0c37dd2;t=57c4ac58f3b98;x=67598e942bd23dc0

__REALTIME_TIMESTAMP=1544035467475864

__MONOTONIC_TIMESTAMP=858200964562

_BOOT_ID=4871e4c474574ce4a462dfe3f1c37f06

PRIORITY=6

_UID=1000

_GID=1000

_CAP_EFFECTIVE=0

_SELINUX_CONTEXT=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023

_AUDIT_SESSION=1

_AUDIT_LOGINUID=1000

_SYSTEMD_OWNER_UID=1000

_SYSTEMD_UNIT=user@1000.service

_SYSTEMD_SLICE=user-1000.slice

_SYSTEMD_USER_SLICE=-.slice

_SYSTEMD_INVOCATION_ID=1c4a469986d448719cb0f9141a10810e

_MACHINE_ID=08a5690a2eed47cf92ac0a5d2e3cf6b0

_HOSTNAME=krowka

_TRANSPORT=syslog

SYSLOG_FACILITY=17

SYSLOG_IDENTIFIER=syslog-caller

MESSAGE=Something logged

_COMM=poc

_EXE=/home/zbyszek/src/systemd-work3/poc

_SYSTEMD_CGROUP=/user.slice/user-1000.slice/user@1000.service/gnome-terminal-server.service

_SYSTEMD_USER_UNIT=gnome-terminal-server.service

SYSLOG_PID=4108

SYSLOG_TIMESTAMP=Dec  5 19:44:27

_PID=4108

_CMDLINE=./poc AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA>

_SOURCE_REALTIME_TIMESTAMP=1544035467475848

$ journalctl -o export -n1 'MESSAGE=Something logged' --output-fields=_CMDLINE|wc

      6    2053 2097410

2MB might be hard for some clients to use meaningfully, but OTOH, it is

important to log the full commandline sometimes. For example, when the program

is crashing, the exact argument list is useful.

(cherry-picked from commit 2d5d2e0cc5171c6795d2a485841474345d9e30ab)

Related: #1664976

---

 src/basic/process-util.c | 73 ++++++++++++++--------------------------

 1 file changed, 25 insertions(+), 48 deletions(-)

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

index 0a4f917cb..a20f1e3cc 100644

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

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

@@ -128,6 +128,13 @@ int get_process_cmdline(pid_t pid, size_t max_length, bool comm_fallback, char *

         (void) __fsetlocking(f, FSETLOCKING_BYCALLER);

+        if (max_length == 0) {

+                /* This is supposed to be a safety guard against runaway command lines. */

+                long l = sysconf(_SC_ARG_MAX);

+                assert(l > 0);

+                max_length = l;

+        }

+

         if (max_length == 1) {

                 /* If there's only room for one byte, return the empty string */

@@ -138,32 +145,6 @@ int get_process_cmdline(pid_t pid, size_t max_length, bool comm_fallback, char *

                 *line = ans;

                 return 0;

-        } else if (max_length == 0) {

-                size_t len = 0, allocated = 0;

-

-                while ((c = getc(f)) != EOF) {

-

-                        if (!GREEDY_REALLOC(ans, allocated, len+3)) {

-                                free(ans);

-                                return -ENOMEM;

-                        }

-

-                        if (isprint(c)) {

-                                if (space) {

-                                        ans[len++] = ' ';

-                                        space = false;

-                                }

-

-                                ans[len++] = c;

-                        } else if (len > 0)

-                                space = true;

-               }

-

-                if (len > 0)

-                        ans[len] = '\0';

-                else

-                        ans = mfree(ans);

-

         } else {

                 bool dotdotdot = false;

                 size_t left;

@@ -235,34 +216,30 @@ int get_process_cmdline(pid_t pid, size_t max_length, bool comm_fallback, char *

                 if (h < 0)

                         return h;

-                if (max_length == 0)

-                        ans = strjoin("[", t, "]");

-                else {

-                        size_t l;

-

-                        l = strlen(t);

+                size_t l = strlen(t);

-                        if (l + 3 <= max_length)

-                                ans = strjoin("[", t, "]");

-                        else if (max_length <= 6) {

+                if (l + 3 <= max_length) {

+                        ans = strjoin("[", t, "]");

+                        if (!ans)

+                                return -ENOMEM;

-                                ans = new(char, max_length);

-                                if (!ans)

-                                        return -ENOMEM;

+                } else if (max_length <= 6) {

+                        ans = new(char, max_length);

+                        if (!ans)

+                                return -ENOMEM;

-                                memcpy(ans, "[...]", max_length-1);

-                                ans[max_length-1] = 0;

-                        } else {

-                                t[max_length - 6] = 0;

+                        memcpy(ans, "[...]", max_length-1);

+                        ans[max_length-1] = 0;

+                } else {

+                        t[max_length - 6] = 0;

-                                /* Chop off final spaces */

-                                delete_trailing_chars(t, WHITESPACE);

+                        /* Chop off final spaces */

+                        delete_trailing_chars(t, WHITESPACE);

-                                ans = strjoin("[", t, "...]");

-                        }

+                        ans = strjoin("[", t, "...]");

+                        if (!ans)

+                                return -ENOMEM;

                 }

-                if (!ans)

-                        return -ENOMEM;

         }

         *line = ans;