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From 625b30e09d0090f81722aa8f02e7057839dfcf4f Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Fri, 9 Feb 2018 17:05:17 +0100
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Subject: [PATCH] service: relax PID file symlink chain checks a bit (#8133)
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Let's read the PID file after all if there's a potentially unsafe
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symlink chain in place. But if we do, then refuse taking the PID if its
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outside of the cgroup.
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Fixes: #8085
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(cherry picked from commit 73969ab61c39357e6892747e43307fbf07cafbed)
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(cherry picked from commit ce87ed7b47c61e649a0f9da39d272631b9524740)
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Resolves: #1729414
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---
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src/core/service.c | 15 +++++++++++++--
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1 file changed, 13 insertions(+), 2 deletions(-)
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diff --git a/src/core/service.c b/src/core/service.c
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index eaa588863f..6b61ccac18 100644
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--- a/src/core/service.c
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+++ b/src/core/service.c
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@@ -736,6 +736,7 @@ static int service_is_suitable_main_pid(Service *s, pid_t pid, int prio) {
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static int service_load_pid_file(Service *s, bool may_warn) {
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char procfs[sizeof("/proc/self/fd/") - 1 + DECIMAL_STR_MAX(int)];
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+ bool questionable_pid_file = false;
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_cleanup_free_ char *k = NULL;
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_cleanup_close_ int fd = -1;
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int r, prio;
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@@ -749,8 +750,13 @@ static int service_load_pid_file(Service *s, bool may_warn) {
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prio = may_warn ? LOG_INFO : LOG_DEBUG;
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fd = chase_symlinks(s->pid_file, NULL, CHASE_OPEN|CHASE_SAFE, NULL);
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- if (fd == -EPERM)
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- return log_unit_full_errno(UNIT(s)->id, prio, fd, "Permission denied while opening PID file or unsafe symlink chain: %s", s->pid_file);
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+ if (fd == -EPERM) {
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+ log_unit_full(UNIT(s)->id, LOG_DEBUG, "Permission denied while opening PID file or potentially unsafe symlink chain, will now retry with relaxed checks: %s", s->pid_file);
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+
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+ questionable_pid_file = true;
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+
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+ fd = chase_symlinks(s->pid_file, NULL, CHASE_OPEN, NULL);
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+ }
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if (fd < 0)
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return log_unit_full_errno(UNIT(s)->id, prio, fd, "Can't open PID file %s (yet?) after %s: %m", s->pid_file, service_state_to_string(s->state));
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@@ -773,6 +779,11 @@ static int service_load_pid_file(Service *s, bool may_warn) {
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if (r == 0) {
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struct stat st;
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+ if (questionable_pid_file) {
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+ log_unit_error(UNIT(s)->id, "Refusing to accept PID outside of service control group, acquired through unsafe symlink chain: %s", s->pid_file);
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+ return -EPERM;
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+ }
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+
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/* Hmm, it's not clear if the new main PID is safe. Let's allow this if the PID file is owned by root */
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if (fstat(fd, &st) < 0)
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