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From c56c1f6c2b683d6f20a7e8caeecec6c3cb76798f Mon Sep 17 00:00:00 2001
From: Lukas Nykryn <lnykryn@redhat.com>
Date: Tue, 3 Jan 2017 14:21:25 +0100
Subject: [PATCH] core: make parsing of RLIMIT_NICE aware of actual nice levels

RHEL-only
(most of code taken from 29857001854a02c292f1f3b324e7a66831e859c8)

Resolves: #1409588
---
 man/systemd.exec.xml                  |  7 ++-
 src/core/load-fragment-gperf.gperf.m4 |  2 +-
 src/core/load-fragment.c              | 72 +++++++++++++++++++++++++++
 src/core/load-fragment.h              |  1 +
 src/core/main.c                       |  2 +-
 5 files changed, 81 insertions(+), 3 deletions(-)

diff --git a/man/systemd.exec.xml b/man/systemd.exec.xml
index 0cd469cd9..c5199d3a5 100644
--- a/man/systemd.exec.xml
+++ b/man/systemd.exec.xml
@@ -575,7 +575,12 @@
         granularity of the limits might influence their
         enforcement. For example, time limits specified for
         <varname>LimitCPU=</varname> will be rounded up implicitly to
-        multiples of 1s.</para>
+        multiples of 1s. For <varname>LimitNICE=</varname> the value
+        may be specified in two syntaxes: if prefixed with <literal>+</literal>
+        or <literal>-</literal>, the value is understood as regular Linux
+        nice value in the range -20..19. If not prefixed like this the value
+        is understood as raw resource limit parameter in the range 0..40 (with 0 being
+        equivalent to 1).</para>
 
         <para>Note that most process resource limits configured with
         these options are per-process, and processes may fork in order
diff --git a/src/core/load-fragment-gperf.gperf.m4 b/src/core/load-fragment-gperf.gperf.m4
index 45d1ead45..f3a6e13d9 100644
--- a/src/core/load-fragment-gperf.gperf.m4
+++ b/src/core/load-fragment-gperf.gperf.m4
@@ -71,7 +71,7 @@ $1.LimitMEMLOCK,                 config_parse_bytes_limit,           RLIMIT_MEML
 $1.LimitLOCKS,                   config_parse_limit,                 RLIMIT_LOCKS,                  offsetof($1, exec_context.rlimit)
 $1.LimitSIGPENDING,              config_parse_limit,                 RLIMIT_SIGPENDING,             offsetof($1, exec_context.rlimit)
 $1.LimitMSGQUEUE,                config_parse_bytes_limit,           RLIMIT_MSGQUEUE,               offsetof($1, exec_context.rlimit)
-$1.LimitNICE,                    config_parse_limit,                 RLIMIT_NICE,                   offsetof($1, exec_context.rlimit)
+$1.LimitNICE,                    config_parse_nice_limit,            RLIMIT_NICE,                   offsetof($1, exec_context.rlimit)
 $1.LimitRTPRIO,                  config_parse_limit,                 RLIMIT_RTPRIO,                 offsetof($1, exec_context.rlimit)
 $1.LimitRTTIME,                  config_parse_usec_limit,            RLIMIT_RTTIME,                 offsetof($1, exec_context.rlimit)
 $1.ReadWriteDirectories,         config_parse_namespace_path_strv,   0,                             offsetof($1, exec_context.read_write_dirs)
diff --git a/src/core/load-fragment.c b/src/core/load-fragment.c
index 705641971..3a3c456da 100644
--- a/src/core/load-fragment.c
+++ b/src/core/load-fragment.c
@@ -1154,6 +1154,56 @@ static int rlim_parse_usec(const char *val, rlim_t *res) {
         return r;
 }
 
+static int rlim_parse_nice(const char *val, rlim_t *ret) {
+        uint64_t rl;
+        int r;
+
+        /* So, Linux is weird. The range for RLIMIT_NICE is 40..1, mapping to the nice levels -20..19. However, the
+         * RLIMIT_NICE limit defaults to 0 by the kernel, i.e. a value that maps to nice level 20, which of course is
+         * bogus and does not exist. In order to permit parsing the RLIMIT_NICE of 0 here we hence implement a slight
+         * asymmetry: when parsing as positive nice level we permit 0..19. When parsing as negative nice level, we
+         * permit -20..0. But when parsing as raw resource limit value then we also allow the special value 0.
+         *
+         * Yeah, Linux is quality engineering sometimes... */
+
+        if (val[0] == '+') {
+
+                /* Prefixed with "+": Parse as positive user-friendly nice value */
+                r = safe_atou64(val + 1, &rl);
+                if (r < 0)
+                        return r;
+
+                if (rl >= PRIO_MAX)
+                        return -ERANGE;
+
+                rl = 20 - rl;
+
+        } else if (val[0] == '-') {
+
+                /* Prefixed with "-": Parse as negative user-friendly nice value */
+                r = safe_atou64(val + 1, &rl);
+                if (r < 0)
+                        return r;
+
+                if (rl > (uint64_t) (-PRIO_MIN))
+                        return -ERANGE;
+
+                rl = 20 + rl;
+        } else {
+
+                /* Not prefixed: parse as raw resource limit value */
+                r = safe_atou64(val, &rl);
+                if (r < 0)
+                        return r;
+
+                if (rl > (uint64_t) (20 - PRIO_MIN))
+                        return -ERANGE;
+        }
+
+        *ret = (rlim_t) rl;
+        return 0;
+}
+
 static int parse_rlimit_range(
                 const char *unit,
                 const char *filename,
@@ -1286,6 +1336,28 @@ int config_parse_usec_limit(
         return parse_rlimit_range(unit, filename, line, rvalue, rl, rlim_parse_usec);
 }
 
+int config_parse_nice_limit(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        struct rlimit **rl = data;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+        assert(data);
+
+        rl += ltype;
+        return parse_rlimit_range(unit, filename, line, rvalue, rl, rlim_parse_nice);
+}
 
 #ifdef HAVE_SYSV_COMPAT
 int config_parse_sysv_priority(const char *unit,
diff --git a/src/core/load-fragment.h b/src/core/load-fragment.h
index 611479612..7c69e5369 100644
--- a/src/core/load-fragment.h
+++ b/src/core/load-fragment.h
@@ -59,6 +59,7 @@ int config_parse_limit(const char *unit, const char *filename, unsigned line, co
 int config_parse_bytes_limit(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_sec_limit(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_usec_limit(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
+int config_parse_nice_limit(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_sysv_priority(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_kill_signal(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_exec_mount_flags(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
diff --git a/src/core/main.c b/src/core/main.c
index 6f8367632..820cbc3e5 100644
--- a/src/core/main.c
+++ b/src/core/main.c
@@ -669,7 +669,7 @@ static int parse_config_file(void) {
                 { "Manager", "DefaultLimitLOCKS",         config_parse_limit,            0, &arg_default_rlimit[RLIMIT_LOCKS]      },
                 { "Manager", "DefaultLimitSIGPENDING",    config_parse_limit,            0, &arg_default_rlimit[RLIMIT_SIGPENDING] },
                 { "Manager", "DefaultLimitMSGQUEUE",      config_parse_bytes_limit,      0, &arg_default_rlimit[RLIMIT_MSGQUEUE]   },
-                { "Manager", "DefaultLimitNICE",          config_parse_limit,            0, &arg_default_rlimit[RLIMIT_NICE]       },
+                { "Manager", "DefaultLimitNICE",          config_parse_nice_limit,       0, &arg_default_rlimit[RLIMIT_NICE]       },
                 { "Manager", "DefaultLimitRTPRIO",        config_parse_limit,            0, &arg_default_rlimit[RLIMIT_RTPRIO]     },
                 { "Manager", "DefaultLimitRTTIME",        config_parse_limit,            0, &arg_default_rlimit[RLIMIT_RTTIME]     },
                 { "Manager", "DefaultCPUAccounting",      config_parse_bool,             0, &arg_default_cpu_accounting            },