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From fd4405b763d26649339069532e79bd45013c8c38 Mon Sep 17 00:00:00 2001
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From: Tomas Mraz <tmraz@fedoraproject.org>
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Date: Mon, 20 Jan 2020 13:58:07 +0100
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Subject: [PATCH] Do not mistake a regular user process for a namespaced one
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In case there is a regular user with a process running on a system
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with uid falling into a namespaced uid range of another user.
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The user with the colliding namespaced uid range will not be
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allowed to be deleted without forcing the action with -f.
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The user_busy() is adjusted to check whether the suspected process
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is really a namespaced process in a different namespace.
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---
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libmisc/user_busy.c | 44 ++++++++++++++++++++++++++++++++++++--------
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1 file changed, 36 insertions(+), 8 deletions(-)
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diff --git a/libmisc/user_busy.c b/libmisc/user_busy.c
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index b0867568..324bb946 100644
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--- a/libmisc/user_busy.c
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+++ b/libmisc/user_busy.c
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@@ -39,6 +39,7 @@
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#include <sys/types.h>
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#include <dirent.h>
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#include <fcntl.h>
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+#include <unistd.h>
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#include "defines.h"
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#include "prototypes.h"
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#ifdef ENABLE_SUBIDS
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@@ -106,6 +107,31 @@ static int user_busy_utmp (const char *name)
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#endif /* !__linux__ */
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#ifdef __linux__
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+#ifdef ENABLE_SUBIDS
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+#define in_parentuid_range(uid) ((uid) >= parentuid && (uid) < parentuid + range)
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+static int different_namespace (const char *sname)
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+{
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+ /* 41: /proc/xxxxxxxxxx/task/xxxxxxxxxx/ns/user + \0 */
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+ char path[41];
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+ char buf[512], buf2[512];
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+ ssize_t llen1, llen2;
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+
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+ snprintf (path, 41, "/proc/%s/ns/user", sname);
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+
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+ if ((llen1 = readlink (path, buf, sizeof(buf))) == -1)
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+ return 0;
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+
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+ if ((llen2 = readlink ("/proc/self/ns/user", buf2, sizeof(buf2))) == -1)
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+ return 0;
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+
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+ if (llen1 == llen2 && memcmp (buf, buf2, llen1) == 0)
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+ return 0; /* same namespace */
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+
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+ return 1;
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+}
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+#endif /* ENABLE_SUBIDS */
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+
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+
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static int check_status (const char *name, const char *sname, uid_t uid)
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{
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/* 40: /proc/xxxxxxxxxx/task/xxxxxxxxxx/status + \0 */
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@@ -114,7 +140,6 @@ static int check_status (const char *name, const char *sname, uid_t uid)
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FILE *sfile;
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snprintf (status, 40, "/proc/%s/status", sname);
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- status[39] = '\0';
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sfile = fopen (status, "r");
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if (NULL == sfile) {
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@@ -123,26 +148,29 @@ static int check_status (const char *name, const char *sname, uid_t uid)
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while (fgets (line, sizeof (line), sfile) == line) {
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if (strncmp (line, "Uid:\t", 5) == 0) {
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unsigned long ruid, euid, suid;
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+
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assert (uid == (unsigned long) uid);
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+ (void) fclose (sfile);
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if (sscanf (line,
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"Uid:\t%lu\t%lu\t%lu\n",
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&ruid, &euid, &suid) == 3) {
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if ( (ruid == (unsigned long) uid)
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|| (euid == (unsigned long) uid)
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- || (suid == (unsigned long) uid)
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+ || (suid == (unsigned long) uid) ) {
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+ return 1;
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+ }
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#ifdef ENABLE_SUBIDS
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- || have_sub_uids(name, ruid, 1)
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- || have_sub_uids(name, euid, 1)
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- || have_sub_uids(name, suid, 1)
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-#endif /* ENABLE_SUBIDS */
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+ if ( different_namespace (sname)
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+ && ( have_sub_uids(name, ruid, 1)
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+ || have_sub_uids(name, euid, 1)
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+ || have_sub_uids(name, suid, 1))
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) {
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- (void) fclose (sfile);
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return 1;
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}
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+#endif /* ENABLE_SUBIDS */
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} else {
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/* Ignore errors. This is just a best effort. */
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}
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- (void) fclose (sfile);
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return 0;
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}
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}
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--
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2.25.2
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