dump: preserve the dumpable flag on criu dump/restore

Preserve the dumpable flag, which affects whether a core dump will be
generated, but also affects the ownership of the virtual files under
/proc/$pid after restoring a process.

Tested: Restored a process with a criu including this patch and looked
at /proc/$pid to confirm that the virtual files were no longer all owned
by root:root.

zdtm tests pass except for cow01 which seems to be broken.
(see https://bugzilla.openvz.org/show_bug.cgi?id=2967 for details.)

This patch fixes https://bugzilla.openvz.org/show_bug.cgi?id=2968

Signed-off-by: Filipe Brandenburger <filbranden@google.com>
Change-Id: I8c386508448a84368a86666f2d7500b252a78bbf
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-dump.c

@@ -471,6 +471,9 @@ static int dump_task_mm(pid_t pid, const struct proc_pid_stat *stat,
 
 	mme.mm_brk = misc->brk;
 
+	mme.dumpable = misc->dumpable;
+	mme.has_dumpable = true;
+
 	mme.n_mm_saved_auxv = AT_VECTOR_SIZE;
 	mme.mm_saved_auxv = xmalloc(pb_repeated_size(&mme, mm_saved_auxv));
 	if (!mme.mm_saved_auxv)

include/parasite.h

@@ -156,6 +156,8 @@ struct parasite_dump_misc {
 	u32 umask;
 
 	struct parasite_dump_thread	ti;
+
+	int dumpable;
 };
 
 #define PARASITE_MAX_GROUPS	(PAGE_SIZE / sizeof(unsigned int) - 2 * sizeof(unsigned))

include/prctl.h

@@ -16,6 +16,12 @@
 #ifndef PR_SET_SECUREBITS
 # define PR_SET_SECUREBITS	28
 #endif
+#ifndef PR_GET_DUMPABLE
+# define PR_GET_DUMPABLE	3
+#endif
+#ifndef PR_SET_DUMPABLE
+# define PR_SET_DUMPABLE	4
+#endif
 
 #ifndef PR_SET_MM
 #define PR_SET_MM		35

pie/parasite.c

@@ -159,6 +159,7 @@ static int dump_misc(struct parasite_dump_misc *args)
 	args->pgid = sys_getpgid(0);
 	args->umask = sys_umask(0);
 	sys_umask(args->umask); /* never fails */
+	args->dumpable = sys_prctl(PR_GET_DUMPABLE, 0, 0, 0, 0);
 
 	return dump_thread_common(&args->ti);
 }

pie/restorer.c

@@ -30,6 +30,7 @@
 #include "restorer.h"
 
 #include "protobuf/creds.pb-c.h"
+#include "protobuf/mm.pb-c.h"
 
 #include "asm/restorer.h"
 
@@ -187,6 +188,21 @@ static int restore_creds(CredsEntry *ce)
 	return 0;
 }
 
+static int restore_dumpable_flag(MmEntry *mme)
+{
+	int ret;
+
+	if (mme->has_dumpable) {
+		ret = sys_prctl(PR_SET_DUMPABLE, mme->dumpable, 0, 0, 0);
+		if (ret) {
+			pr_err("Unable to set PR_SET_DUMPABLE: %d\n", ret);
+			return -1;
+		}
+	}
+
+	return 0;
+}
+
 static void restore_sched_info(struct rst_sched_param *p)
 {
 	struct sched_param parm;
@@ -295,6 +311,10 @@ long __export_restore_thread(struct thread_restore_args *args)
 	if (ret)
 		goto core_restore_end;
 
+	ret = restore_dumpable_flag(&args->ta->mm);
+	if (ret)
+		goto core_restore_end;
+
 	pr_info("%ld: Restored\n", sys_gettid());
 
 	restore_finish_stage(CR_STATE_RESTORE);
@@ -918,6 +938,7 @@ long __export_restore_task(struct task_restore_args *args)
 	 */
 
 	ret = restore_creds(&args->creds);
+	ret = ret || restore_dumpable_flag(&args->mm);
 
 	futex_set_and_wake(&thread_inprogress, args->nr_threads);
 

protobuf/mm.proto

@@ -17,4 +17,6 @@ message mm_entry {
 	repeated uint64	mm_saved_auxv	= 13;
 
 	repeated vma_entry vmas		= 14;
+
+	optional int32	dumpable	= 15;
 }