dump: Don't dump file params with on-stack values

Otherwise I see output like

 | Dumping path for 1536412160 fd via self 27 [/usr/bin/screen]

where fd is taken from stack and what is worse -- we work
with root privilegues, thus dumping _anything_ from stack
is very bad idea.

With explicitly cleared stack data and FD_DESC_INVALID the
log file will have an entry like

 | Dumping path for -3 fd via self 27 [/usr/bin/screen]
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-dump.c

@@ -354,7 +354,7 @@ static int dump_reg_file(struct fd_parms *p, int lfd,
 
 static int dump_task_exe_link(pid_t pid, struct mm_entry *mm)
 {
-	struct fd_parms params;
+	struct fd_parms params = { };
 	int fd, ret;
 
 	fd = open_proc(pid, "exe");
@@ -366,9 +366,7 @@ static int dump_task_exe_link(pid_t pid, struct mm_entry *mm)
 		return -1;
 	}
 
-	params.flags = 0;
-	params.pos = 0;
-	params.fown = (fown_t){ };
+	params.fd = FD_DESC_INVALID;
 	mm->exe_file_id = fd_id_generate_special();
 
 	ret = dump_one_reg_file(fd, mm->exe_file_id, &params);
@@ -593,15 +591,14 @@ static int dump_task_fs(pid_t pid, struct cr_fdset *fdset)
 static int dump_filemap(pid_t pid, struct vma_entry *vma, int file_fd,
 		const struct cr_fdset *fdset)
 {
-	struct fd_parms p;
+	struct fd_parms p = { };
 
 	if (fstat(file_fd, &p.stat) < 0) {
 		pr_perror("Can't stat file for vma");
 		return -1;
 	}
 
-	p.pos = 0;
-	p.fown = (fown_t){ };
+	p.fd = FD_DESC_INVALID;
 	if ((vma->prot & PROT_WRITE) && vma_entry_is(vma, VMA_FILE_SHARED))
 		p.flags = O_RDWR;
 	else

include/file-ids.h

@@ -7,6 +7,7 @@
 
 #define FD_ID_INVALID		(-1U)
 #define FD_PID_INVALID		(-2U)
+#define FD_DESC_INVALID		(-3U)
 
 #define MAKE_FD_GENID(dev, ino, pos) \
 	(((u32)(dev) ^ (u32)(ino) ^ (u32)(pos)))